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gerrit.openfyde.cn / chromium.googlesource.com / chromium / deps / sqlite / bbce338412255f7aa5539c2bc6575f954d1ccae4 / . / src / btree.c
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/*
** 2004 April 6
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.545 2008/12/05 22:40:08 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"
/*
** The header string that appears at the beginning of every
** SQLite database.
*/
static const char zMagicHeader[] = SQLITE_FILE_HEADER;
/*
** Set this global variable to 1 to enable tracing using the TRACE
** macro.
*/
#if 0
int sqlite3BtreeTrace=0; /* True to enable tracing */
# define TRACE(X) if(sqlite3BtreeTrace){printf X;fflush(stdout);}
#else
# define TRACE(X)
#endif
/*
** Sometimes we need a small amount of code such as a variable initialization
** to setup for a later assert() statement. We do not want this code to
** appear when assert() is disabled. The following macro is therefore
** used to contain that setup code. The "VVA" acronym stands for
** "Verification, Validation, and Accreditation". In other words, the
** code within VVA_ONLY() will only run during verification processes.
*/
#ifndef NDEBUG
# define VVA_ONLY(X) X
#else
# define VVA_ONLY(X)
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** A list of BtShared objects that are eligible for participation
** in shared cache. This variable has file scope during normal builds,
** but the test harness needs to access it so we make it global for
** test builds.
*/
#ifdef SQLITE_TEST
BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
#else
static BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
#endif
#endif /* SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Enable or disable the shared pager and schema features.
**
** This routine has no effect on existing database connections.
** The shared cache setting effects only future calls to
** sqlite3_open(), sqlite3_open16(), or sqlite3_open_v2().
*/
int sqlite3_enable_shared_cache(int enable){
sqlite3GlobalConfig.sharedCacheEnabled = enable;
return SQLITE_OK;
}
#endif
/*
** Forward declaration
*/
static int checkReadLocks(Btree*, Pgno, BtCursor*, i64);
#ifdef SQLITE_OMIT_SHARED_CACHE
/*
** The functions queryTableLock(), lockTable() and unlockAllTables()
** manipulate entries in the BtShared.pLock linked list used to store
** shared-cache table level locks. If the library is compiled with the
** shared-cache feature disabled, then there is only ever one user
** of each BtShared structure and so this locking is not necessary.
** So define the lock related functions as no-ops.
*/
#define queryTableLock(a,b,c) SQLITE_OK
#define lockTable(a,b,c) SQLITE_OK
#define unlockAllTables(a)
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Query to see if btree handle p may obtain a lock of type eLock
** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
** SQLITE_OK if the lock may be obtained (by calling lockTable()), or
** SQLITE_LOCKED if not.
*/
static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
assert( p->db!=0 );
/* This is a no-op if the shared-cache is not enabled */
if( !p->sharable ){
return SQLITE_OK;
}
/* If some other connection is holding an exclusive lock, the
** requested lock may not be obtained.
*/
if( pBt->pExclusive && pBt->pExclusive!=p ){
return SQLITE_LOCKED;
}
/* This (along with lockTable()) is where the ReadUncommitted flag is
** dealt with. If the caller is querying for a read-lock and the flag is
** set, it is unconditionally granted - even if there are write-locks
** on the table. If a write-lock is requested, the ReadUncommitted flag
** is not considered.
**
** In function lockTable(), if a read-lock is demanded and the
** ReadUncommitted flag is set, no entry is added to the locks list
** (BtShared.pLock).
**
** To summarize: If the ReadUncommitted flag is set, then read cursors do
** not create or respect table locks. The locking procedure for a
** write-cursor does not change.
*/
if(
0==(p->db->flags&SQLITE_ReadUncommitted) ||
eLock==WRITE_LOCK ||
iTab==MASTER_ROOT
){
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->pBtree!=p && pIter->iTable==iTab &&
(pIter->eLock!=eLock || eLock!=READ_LOCK) ){
return SQLITE_LOCKED;
}
}
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Add a lock on the table with root-page iTable to the shared-btree used
** by Btree handle p. Parameter eLock must be either READ_LOCK or
** WRITE_LOCK.
**
** SQLITE_OK is returned if the lock is added successfully. SQLITE_BUSY and
** SQLITE_NOMEM may also be returned.
*/
static int lockTable(Btree *p, Pgno iTable, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pLock = 0;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
assert( p->db!=0 );
/* This is a no-op if the shared-cache is not enabled */
if( !p->sharable ){
return SQLITE_OK;
}
assert( SQLITE_OK==queryTableLock(p, iTable, eLock) );
/* If the read-uncommitted flag is set and a read-lock is requested,
** return early without adding an entry to the BtShared.pLock list. See
** comment in function queryTableLock() for more info on handling
** the ReadUncommitted flag.
*/
if(
(p->db->flags&SQLITE_ReadUncommitted) &&
(eLock==READ_LOCK) &&
iTable!=MASTER_ROOT
){
return SQLITE_OK;
}
/* First search the list for an existing lock on this table. */
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->iTable==iTable && pIter->pBtree==p ){
pLock = pIter;
break;
}
}
/* If the above search did not find a BtLock struct associating Btree p
** with table iTable, allocate one and link it into the list.
*/
if( !pLock ){
pLock = (BtLock *)sqlite3MallocZero(sizeof(BtLock));
if( !pLock ){
return SQLITE_NOMEM;
}
pLock->iTable = iTable;
pLock->pBtree = p;
pLock->pNext = pBt->pLock;
pBt->pLock = pLock;
}
/* Set the BtLock.eLock variable to the maximum of the current lock
** and the requested lock. This means if a write-lock was already held
** and a read-lock requested, we don't incorrectly downgrade the lock.
*/
assert( WRITE_LOCK>READ_LOCK );
if( eLock>pLock->eLock ){
pLock->eLock = eLock;
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Release all the table locks (locks obtained via calls to the lockTable()
** procedure) held by Btree handle p.
*/
static void unlockAllTables(Btree *p){
BtShared *pBt = p->pBt;
BtLock **ppIter = &pBt->pLock;
assert( sqlite3BtreeHoldsMutex(p) );
assert( p->sharable || 0==*ppIter );
while( *ppIter ){
BtLock *pLock = *ppIter;
assert( pBt->pExclusive==0 || pBt->pExclusive==pLock->pBtree );
if( pLock->pBtree==p ){
*ppIter = pLock->pNext;
sqlite3_free(pLock);
}else{
ppIter = &pLock->pNext;
}
}
if( pBt->pExclusive==p ){
pBt->pExclusive = 0;
}
}
#endif /* SQLITE_OMIT_SHARED_CACHE */
static void releasePage(MemPage *pPage); /* Forward reference */
/*
** Verify that the cursor holds a mutex on the BtShared
*/
#ifndef NDEBUG
static int cursorHoldsMutex(BtCursor *p){
return sqlite3_mutex_held(p->pBt->mutex);
}
#endif
#ifndef SQLITE_OMIT_INCRBLOB
/*
** Invalidate the overflow page-list cache for cursor pCur, if any.
*/
static void invalidateOverflowCache(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
sqlite3_free(pCur->aOverflow);
pCur->aOverflow = 0;
}
/*
** Invalidate the overflow page-list cache for all cursors opened
** on the shared btree structure pBt.
*/
static void invalidateAllOverflowCache(BtShared *pBt){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
for(p=pBt->pCursor; p; p=p->pNext){
invalidateOverflowCache(p);
}
}
#else
#define invalidateOverflowCache(x)
#define invalidateAllOverflowCache(x)
#endif
/*
** Save the current cursor position in the variables BtCursor.nKey
** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
*/
static int saveCursorPosition(BtCursor *pCur){
int rc;
assert( CURSOR_VALID==pCur->eState );
assert( 0==pCur->pKey );
assert( cursorHoldsMutex(pCur) );
rc = sqlite3BtreeKeySize(pCur, &pCur->nKey);
/* If this is an intKey table, then the above call to BtreeKeySize()
** stores the integer key in pCur->nKey. In this case this value is
** all that is required. Otherwise, if pCur is not open on an intKey
** table, then malloc space for and store the pCur->nKey bytes of key
** data.
*/
if( rc==SQLITE_OK && 0==pCur->apPage[0]->intKey){
void *pKey = sqlite3Malloc(pCur->nKey);
if( pKey ){
rc = sqlite3BtreeKey(pCur, 0, pCur->nKey, pKey);
if( rc==SQLITE_OK ){
pCur->pKey = pKey;
}else{
sqlite3_free(pKey);
}
}else{
rc = SQLITE_NOMEM;
}
}
assert( !pCur->apPage[0]->intKey || !pCur->pKey );
if( rc==SQLITE_OK ){
int i;
for(i=0; i<=pCur->iPage; i++){
releasePage(pCur->apPage[i]);
pCur->apPage[i] = 0;
}
pCur->iPage = -1;
pCur->eState = CURSOR_REQUIRESEEK;
}
invalidateOverflowCache(pCur);
return rc;
}
/*
** Save the positions of all cursors except pExcept open on the table
** with root-page iRoot. Usually, this is called just before cursor
** pExcept is used to modify the table (BtreeDelete() or BtreeInsert()).
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pExcept==0 || pExcept->pBt==pBt );
for(p=pBt->pCursor; p; p=p->pNext){
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) &&
p->eState==CURSOR_VALID ){
int rc = saveCursorPosition(p);
if( SQLITE_OK!=rc ){
return rc;
}
}
}
return SQLITE_OK;
}
/*
** Clear the current cursor position.
*/
void sqlite3BtreeClearCursor(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
pCur->eState = CURSOR_INVALID;
}
/*
** Restore the cursor to the position it was in (or as close to as possible)
** when saveCursorPosition() was called. Note that this call deletes the
** saved position info stored by saveCursorPosition(), so there can be
** at most one effective restoreCursorPosition() call after each
** saveCursorPosition().
*/
int sqlite3BtreeRestoreCursorPosition(BtCursor *pCur){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState>=CURSOR_REQUIRESEEK );
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
pCur->eState = CURSOR_INVALID;
rc = sqlite3BtreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &pCur->skip);
if( rc==SQLITE_OK ){
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
}
return rc;
}
#define restoreCursorPosition(p) \
(p->eState>=CURSOR_REQUIRESEEK ? \
sqlite3BtreeRestoreCursorPosition(p) : \
SQLITE_OK)
/*
** Determine whether or not a cursor has moved from the position it
** was last placed at. Cursors can move when the row they are pointing
** at is deleted out from under them.
**
** This routine returns an error code if something goes wrong. The
** integer *pHasMoved is set to one if the cursor has moved and 0 if not.
*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
int rc;
rc = restoreCursorPosition(pCur);
if( rc ){
*pHasMoved = 1;
return rc;
}
if( pCur->eState!=CURSOR_VALID || pCur->skip!=0 ){
*pHasMoved = 1;
}else{
*pHasMoved = 0;
}
return SQLITE_OK;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the
** input page number.
*/
static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
int nPagesPerMapPage;
Pgno iPtrMap, ret;
assert( sqlite3_mutex_held(pBt->mutex) );
nPagesPerMapPage = (pBt->usableSize/5)+1;
iPtrMap = (pgno-2)/nPagesPerMapPage;
ret = (iPtrMap*nPagesPerMapPage) + 2;
if( ret==PENDING_BYTE_PAGE(pBt) ){
ret++;
}
return ret;
}
/*
** Write an entry into the pointer map.
**
** This routine updates the pointer map entry for page number 'key'
** so that it maps to type 'eType' and parent page number 'pgno'.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent){
DbPage *pDbPage; /* The pointer map page */
u8 *pPtrmap; /* The pointer map data */
Pgno iPtrmap; /* The pointer map page number */
int offset; /* Offset in pointer map page */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
/* The master-journal page number must never be used as a pointer map page */
assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );
assert( pBt->autoVacuum );
if( key==0 ){
return SQLITE_CORRUPT_BKPT;
}
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
offset = PTRMAP_PTROFFSET(iPtrmap, key);
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
rc = sqlite3PagerWrite(pDbPage);
if( rc==SQLITE_OK ){
pPtrmap[offset] = eType;
put4byte(&pPtrmap[offset+1], parent);
}
}
sqlite3PagerUnref(pDbPage);
return rc;
}
/*
** Read an entry from the pointer map.
**
** This routine retrieves the pointer map entry for page 'key', writing
** the type and parent page number to *pEType and *pPgno respectively.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
DbPage *pDbPage; /* The pointer map page */
int iPtrmap; /* Pointer map page index */
u8 *pPtrmap; /* Pointer map page data */
int offset; /* Offset of entry in pointer map */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
if( rc!=0 ){
return rc;
}
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
offset = PTRMAP_PTROFFSET(iPtrmap, key);
assert( pEType!=0 );
*pEType = pPtrmap[offset];
if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
sqlite3PagerUnref(pDbPage);
if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
return SQLITE_OK;
}
#else /* if defined SQLITE_OMIT_AUTOVACUUM */
#define ptrmapPut(w,x,y,z) SQLITE_OK
#define ptrmapGet(w,x,y,z) SQLITE_OK
#define ptrmapPutOvfl(y,z) SQLITE_OK
#endif
/*
** Given a btree page and a cell index (0 means the first cell on
** the page, 1 means the second cell, and so forth) return a pointer
** to the cell content.
**
** This routine works only for pages that do not contain overflow cells.
*/
#define findCell(P,I) \
((P)->aData + ((P)->maskPage & get2byte(&(P)->aData[(P)->cellOffset+2*(I)])))
/*
** This a more complex version of findCell() that works for
** pages that do contain overflow cells. See insert
*/
static u8 *findOverflowCell(MemPage *pPage, int iCell){
int i;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
for(i=pPage->nOverflow-1; i>=0; i--){
int k;
struct _OvflCell *pOvfl;
pOvfl = &pPage->aOvfl[i];
k = pOvfl->idx;
if( k<=iCell ){
if( k==iCell ){
return pOvfl->pCell;
}
iCell--;
}
}
return findCell(pPage, iCell);
}
/*
** Parse a cell content block and fill in the CellInfo structure. There
** are two versions of this function. sqlite3BtreeParseCell() takes a
** cell index as the second argument and sqlite3BtreeParseCellPtr()
** takes a pointer to the body of the cell as its second argument.
**
** Within this file, the parseCell() macro can be called instead of
** sqlite3BtreeParseCellPtr(). Using some compilers, this will be faster.
*/
void sqlite3BtreeParseCellPtr(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
int n; /* Number bytes in cell content header */
u32 nPayload; /* Number of bytes of cell payload */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pInfo->pCell = pCell;
assert( pPage->leaf==0 || pPage->leaf==1 );
n = pPage->childPtrSize;
assert( n==4-4*pPage->leaf );
if( pPage->intKey ){
if( pPage->hasData ){
n += getVarint32(&pCell[n], nPayload);
}else{
nPayload = 0;
}
n += getVarint(&pCell[n], (u64*)&pInfo->nKey);
pInfo->nData = nPayload;
}else{
pInfo->nData = 0;
n += getVarint32(&pCell[n], nPayload);
pInfo->nKey = nPayload;
}
pInfo->nPayload = nPayload;
pInfo->nHeader = n;
if( likely(nPayload<=pPage->maxLocal) ){
/* This is the (easy) common case where the entire payload fits
** on the local page. No overflow is required.
*/
int nSize; /* Total size of cell content in bytes */
nSize = nPayload + n;
pInfo->nLocal = nPayload;
pInfo->iOverflow = 0;
if( (nSize & ~3)==0 ){
nSize = 4; /* Minimum cell size is 4 */
}
pInfo->nSize = nSize;
}else{
/* If the payload will not fit completely on the local page, we have
** to decide how much to store locally and how much to spill onto
** overflow pages. The strategy is to minimize the amount of unused
** space on overflow pages while keeping the amount of local storage
** in between minLocal and maxLocal.
**
** Warning: changing the way overflow payload is distributed in any
** way will result in an incompatible file format.
*/
int minLocal; /* Minimum amount of payload held locally */
int maxLocal; /* Maximum amount of payload held locally */
int surplus; /* Overflow payload available for local storage */
minLocal = pPage->minLocal;
maxLocal = pPage->maxLocal;
surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize - 4);
if( surplus <= maxLocal ){
pInfo->nLocal = surplus;
}else{
pInfo->nLocal = minLocal;
}
pInfo->iOverflow = pInfo->nLocal + n;
pInfo->nSize = pInfo->iOverflow + 4;
}
}
#define parseCell(pPage, iCell, pInfo) \
sqlite3BtreeParseCellPtr((pPage), findCell((pPage), (iCell)), (pInfo))
void sqlite3BtreeParseCell(
MemPage *pPage, /* Page containing the cell */
int iCell, /* The cell index. First cell is 0 */
CellInfo *pInfo /* Fill in this structure */
){
parseCell(pPage, iCell, pInfo);
}
/*
** Compute the total number of bytes that a Cell needs in the cell
** data area of the btree-page. The return number includes the cell
** data header and the local payload, but not any overflow page or
** the space used by the cell pointer.
*/
#ifndef NDEBUG
static u16 cellSize(MemPage *pPage, int iCell){
CellInfo info;
sqlite3BtreeParseCell(pPage, iCell, &info);
return info.nSize;
}
#endif
static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
CellInfo info;
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
return info.nSize;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** If the cell pCell, part of page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static int ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell){
CellInfo info;
assert( pCell!=0 );
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
if( (info.nData+(pPage->intKey?0:info.nKey))>info.nLocal ){
Pgno ovfl = get4byte(&pCell[info.iOverflow]);
return ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno);
}
return SQLITE_OK;
}
/*
** If the cell with index iCell on page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static int ptrmapPutOvfl(MemPage *pPage, int iCell){
u8 *pCell;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pCell = findOverflowCell(pPage, iCell);
return ptrmapPutOvflPtr(pPage, pCell);
}
#endif
/*
** Defragment the page given. All Cells are moved to the
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
*/
static int defragmentPage(MemPage *pPage){
int i; /* Loop counter */
int pc; /* Address of a i-th cell */
int addr; /* Offset of first byte after cell pointer array */
int hdr; /* Offset to the page header */
int size; /* Size of a cell */
int usableSize; /* Number of usable bytes on a page */
int cellOffset; /* Offset to the cell pointer array */
int cbrk; /* Offset to the cell content area */
int nCell; /* Number of cells on the page */
unsigned char *data; /* The page data */
unsigned char *temp; /* Temp area for cell content */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt!=0 );
assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
assert( pPage->nOverflow==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
data = pPage->aData;
hdr = pPage->hdrOffset;
cellOffset = pPage->cellOffset;
nCell = pPage->nCell;
assert( nCell==get2byte(&data[hdr+3]) );
usableSize = pPage->pBt->usableSize;
cbrk = get2byte(&data[hdr+5]);
memcpy(&temp[cbrk], &data[cbrk], usableSize - cbrk);
cbrk = usableSize;
for(i=0; i<nCell; i++){
u8 *pAddr; /* The i-th cell pointer */
pAddr = &data[cellOffset + i*2];
pc = get2byte(pAddr);
if( pc>=usableSize ){
return SQLITE_CORRUPT_BKPT;
}
size = cellSizePtr(pPage, &temp[pc]);
cbrk -= size;
if( cbrk<cellOffset+2*nCell || pc+size>usableSize ){
return SQLITE_CORRUPT_BKPT;
}
assert( cbrk+size<=usableSize && cbrk>=0 );
memcpy(&data[cbrk], &temp[pc], size);
put2byte(pAddr, cbrk);
}
assert( cbrk>=cellOffset+2*nCell );
put2byte(&data[hdr+5], cbrk);
data[hdr+1] = 0;
data[hdr+2] = 0;
data[hdr+7] = 0;
addr = cellOffset+2*nCell;
memset(&data[addr], 0, cbrk-addr);
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
if( cbrk-addr!=pPage->nFree ){
return SQLITE_CORRUPT_BKPT;
}
return SQLITE_OK;
}
/*
** Allocate nByte bytes of space on a page.
**
** Return the index into pPage->aData[] of the first byte of
** the new allocation. The caller guarantees that there is enough
** space. This routine will never fail.
**
** If the page contains nBytes of free space but does not contain
** nBytes of contiguous free space, then this routine automatically
** calls defragementPage() to consolidate all free space before
** allocating the new chunk.
*/
static int allocateSpace(MemPage *pPage, int nByte){
int addr, pc, hdr;
int size;
int nFrag;
int top;
int nCell;
int cellOffset;
unsigned char *data;
data = pPage->aData;
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( nByte>=0 ); /* Minimum cell size is 4 */
assert( pPage->nFree>=nByte );
assert( pPage->nOverflow==0 );
pPage->nFree -= nByte;
hdr = pPage->hdrOffset;
nFrag = data[hdr+7];
if( nFrag<60 ){
/* Search the freelist looking for a slot big enough to satisfy the
** space request. */
addr = hdr+1;
while( (pc = get2byte(&data[addr]))>0 ){
size = get2byte(&data[pc+2]);
if( size>=nByte ){
if( size<nByte+4 ){
memcpy(&data[addr], &data[pc], 2);
data[hdr+7] = nFrag + size - nByte;
return pc;
}else{
put2byte(&data[pc+2], size-nByte);
return pc + size - nByte;
}
}
addr = pc;
}
}
/* Allocate memory from the gap in between the cell pointer array
** and the cell content area.
*/
top = get2byte(&data[hdr+5]);
nCell = get2byte(&data[hdr+3]);
cellOffset = pPage->cellOffset;
if( nFrag>=60 || cellOffset + 2*nCell > top - nByte ){
defragmentPage(pPage);
top = get2byte(&data[hdr+5]);
}
top -= nByte;
assert( cellOffset + 2*nCell <= top );
put2byte(&data[hdr+5], top);
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
return top;
}
/*
** Return a section of the pPage->aData to the freelist.
** The first byte of the new free block is pPage->aDisk[start]
** and the size of the block is "size" bytes.
**
** Most of the effort here is involved in coalesing adjacent
** free blocks into a single big free block.
*/
static int freeSpace(MemPage *pPage, int start, int size){
int addr, pbegin, hdr;
unsigned char *data = pPage->aData;
assert( pPage->pBt!=0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
assert( (start + size)<=pPage->pBt->usableSize );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( size>=0 ); /* Minimum cell size is 4 */
#ifdef SQLITE_SECURE_DELETE
/* Overwrite deleted information with zeros when the SECURE_DELETE
** option is enabled at compile-time */
memset(&data[start], 0, size);
#endif
/* Add the space back into the linked list of freeblocks */
hdr = pPage->hdrOffset;
addr = hdr + 1;
while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
assert( pbegin<=pPage->pBt->usableSize-4 );
if( pbegin<=addr ) {
return SQLITE_CORRUPT_BKPT;
}
addr = pbegin;
}
if ( pbegin>pPage->pBt->usableSize-4 ) {
return SQLITE_CORRUPT_BKPT;
}
assert( pbegin>addr || pbegin==0 );
put2byte(&data[addr], start);
put2byte(&data[start], pbegin);
put2byte(&data[start+2], size);
pPage->nFree += size;
/* Coalesce adjacent free blocks */
addr = pPage->hdrOffset + 1;
while( (pbegin = get2byte(&data[addr]))>0 ){
int pnext, psize;
assert( pbegin>addr );
assert( pbegin<=pPage->pBt->usableSize-4 );
pnext = get2byte(&data[pbegin]);
psize = get2byte(&data[pbegin+2]);
if( pbegin + psize + 3 >= pnext && pnext>0 ){
int frag = pnext - (pbegin+psize);
if( (frag<0) || (frag>data[pPage->hdrOffset+7]) ){
return SQLITE_CORRUPT_BKPT;
}
data[pPage->hdrOffset+7] -= frag;
put2byte(&data[pbegin], get2byte(&data[pnext]));
put2byte(&data[pbegin+2], pnext+get2byte(&data[pnext+2])-pbegin);
}else{
addr = pbegin;
}
}
/* If the cell content area begins with a freeblock, remove it. */
if( data[hdr+1]==data[hdr+5] && data[hdr+2]==data[hdr+6] ){
int top;
pbegin = get2byte(&data[hdr+1]);
memcpy(&data[hdr+1], &data[pbegin], 2);
top = get2byte(&data[hdr+5]);
put2byte(&data[hdr+5], top + get2byte(&data[pbegin+2]));
}
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
return SQLITE_OK;
}
/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
**
** Only the following combinations are supported. Anything different
** indicates a corrupt database files:
**
** PTF_ZERODATA
** PTF_ZERODATA | PTF_LEAF
** PTF_LEAFDATA | PTF_INTKEY
** PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF
*/
static int decodeFlags(MemPage *pPage, int flagByte){
BtShared *pBt; /* A copy of pPage->pBt */
assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->leaf = flagByte>>3; assert( PTF_LEAF == 1<<3 );
flagByte &= ~PTF_LEAF;
pPage->childPtrSize = 4-4*pPage->leaf;
pBt = pPage->pBt;
if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
pPage->intKey = 1;
pPage->hasData = pPage->leaf;
pPage->maxLocal = pBt->maxLeaf;
pPage->minLocal = pBt->minLeaf;
}else if( flagByte==PTF_ZERODATA ){
pPage->intKey = 0;
pPage->hasData = 0;
pPage->maxLocal = pBt->maxLocal;
pPage->minLocal = pBt->minLocal;
}else{
return SQLITE_CORRUPT_BKPT;
}
return SQLITE_OK;
}
/*
** Initialize the auxiliary information for a disk block.
**
** Return SQLITE_OK on success. If we see that the page does
** not contain a well-formed database page, then return
** SQLITE_CORRUPT. Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed. It only shows that
** we failed to detect any corruption.
*/
int sqlite3BtreeInitPage(MemPage *pPage){
assert( pPage->pBt!=0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
if( !pPage->isInit ){
int pc; /* Address of a freeblock within pPage->aData[] */
int hdr; /* Offset to beginning of page header */
u8 *data; /* Equal to pPage->aData */
BtShared *pBt; /* The main btree structure */
int usableSize; /* Amount of usable space on each page */
int cellOffset; /* Offset from start of page to first cell pointer */
int nFree; /* Number of unused bytes on the page */
int top; /* First byte of the cell content area */
pBt = pPage->pBt;
hdr = pPage->hdrOffset;
data = pPage->aData;
if( decodeFlags(pPage, data[hdr]) ) return SQLITE_CORRUPT_BKPT;
assert( pBt->pageSize>=512 && pBt->pageSize<=32768 );
pPage->maskPage = pBt->pageSize - 1;
pPage->nOverflow = 0;
usableSize = pBt->usableSize;
pPage->cellOffset = cellOffset = hdr + 12 - 4*pPage->leaf;
top = get2byte(&data[hdr+5]);
pPage->nCell = get2byte(&data[hdr+3]);
if( pPage->nCell>MX_CELL(pBt) ){
/* To many cells for a single page. The page must be corrupt */
return SQLITE_CORRUPT_BKPT;
}
/* Compute the total free space on the page */
pc = get2byte(&data[hdr+1]);
nFree = data[hdr+7] + top - (cellOffset + 2*pPage->nCell);
while( pc>0 ){
int next, size;
if( pc>usableSize-4 ){
/* Free block is off the page */
return SQLITE_CORRUPT_BKPT;
}
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
if( next>0 && next<=pc+size+3 ){
/* Free blocks must be in accending order */
return SQLITE_CORRUPT_BKPT;
}
nFree += size;
pc = next;
}
pPage->nFree = nFree;
if( nFree>=usableSize ){
/* Free space cannot exceed total page size */
return SQLITE_CORRUPT_BKPT;
}
#if 0
/* Check that all the offsets in the cell offset array are within range.
**
** Omitting this consistency check and using the pPage->maskPage mask
** to prevent overrunning the page buffer in findCell() results in a
** 2.5% performance gain.
*/
{
u8 *pOff; /* Iterator used to check all cell offsets are in range */
u8 *pEnd; /* Pointer to end of cell offset array */
u8 mask; /* Mask of bits that must be zero in MSB of cell offsets */
mask = ~(((u8)(pBt->pageSize>>8))-1);
pEnd = &data[cellOffset + pPage->nCell*2];
for(pOff=&data[cellOffset]; pOff!=pEnd && !((*pOff)&mask); pOff+=2);
if( pOff!=pEnd ){
return SQLITE_CORRUPT_BKPT;
}
}
#endif
pPage->isInit = 1;
}
return SQLITE_OK;
}
/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage, int flags){
unsigned char *data = pPage->aData;
BtShared *pBt = pPage->pBt;
int hdr = pPage->hdrOffset;
int first;
assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage) == data );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pBt->mutex) );
/*memset(&data[hdr], 0, pBt->usableSize - hdr);*/
data[hdr] = flags;
first = hdr + 8 + 4*((flags&PTF_LEAF)==0);
memset(&data[hdr+1], 0, 4);
data[hdr+7] = 0;
put2byte(&data[hdr+5], pBt->usableSize);
pPage->nFree = pBt->usableSize - first;
decodeFlags(pPage, flags);
pPage->hdrOffset = hdr;
pPage->cellOffset = first;
pPage->nOverflow = 0;
assert( pBt->pageSize>=512 && pBt->pageSize<=32768 );
pPage->maskPage = pBt->pageSize - 1;
pPage->nCell = 0;
pPage->isInit = 1;
}
/*
** Convert a DbPage obtained from the pager into a MemPage used by
** the btree layer.
*/
static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
MemPage *pPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
pPage->aData = sqlite3PagerGetData(pDbPage);
pPage->pDbPage = pDbPage;
pPage->pBt = pBt;
pPage->pgno = pgno;
pPage->hdrOffset = pPage->pgno==1 ? 100 : 0;
return pPage;
}
/*
** Get a page from the pager. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
**
** If the noContent flag is set, it means that we do not care about
** the content of the page at this time. So do not go to the disk
** to fetch the content. Just fill in the content with zeros for now.
** If in the future we call sqlite3PagerWrite() on this page, that
** means we have started to be concerned about content and the disk
** read should occur at that point.
*/
int sqlite3BtreeGetPage(
BtShared *pBt, /* The btree */
Pgno pgno, /* Number of the page to fetch */
MemPage **ppPage, /* Return the page in this parameter */
int noContent /* Do not load page content if true */
){
int rc;
DbPage *pDbPage;
assert( sqlite3_mutex_held(pBt->mutex) );
rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, noContent);
if( rc ) return rc;
*ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
return SQLITE_OK;
}
/*
** Return the size of the database file in pages. If there is any kind of
** error, return ((unsigned int)-1).
*/
static Pgno pagerPagecount(BtShared *pBt){
int nPage = -1;
int rc;
assert( pBt->pPage1 );
rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
assert( rc==SQLITE_OK || nPage==-1 );
return (Pgno)nPage;
}
/*
** Get a page from the pager and initialize it. This routine
** is just a convenience wrapper around separate calls to
** sqlite3BtreeGetPage() and sqlite3BtreeInitPage().
*/
static int getAndInitPage(
BtShared *pBt, /* The database file */
Pgno pgno, /* Number of the page to get */
MemPage **ppPage /* Write the page pointer here */
){
int rc;
DbPage *pDbPage;
MemPage *pPage;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno==0 ){
return SQLITE_CORRUPT_BKPT;
}
/* It is often the case that the page we want is already in cache.
** If so, get it directly. This saves us from having to call
** pagerPagecount() to make sure pgno is within limits, which results
** in a measureable performance improvements.
*/
pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
if( pDbPage ){
/* Page is already in cache */
*ppPage = pPage = btreePageFromDbPage(pDbPage, pgno, pBt);
rc = SQLITE_OK;
}else{
/* Page not in cache. Acquire it. */
if( pgno>pagerPagecount(pBt) ){
return SQLITE_CORRUPT_BKPT;
}
rc = sqlite3BtreeGetPage(pBt, pgno, ppPage, 0);
if( rc ) return rc;
pPage = *ppPage;
}
if( !pPage->isInit ){
rc = sqlite3BtreeInitPage(pPage);
}
if( rc!=SQLITE_OK ){
releasePage(pPage);
*ppPage = 0;
}
return rc;
}
/*
** Release a MemPage. This should be called once for each prior
** call to sqlite3BtreeGetPage.
*/
static void releasePage(MemPage *pPage){
if( pPage ){
assert( pPage->aData );
assert( pPage->pBt );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
sqlite3PagerUnref(pPage->pDbPage);
}
}
/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
** the transaction, for each page restored this routine is called.
**
** This routine needs to reset the extra data section at the end of the
** page to agree with the restored data.
*/
static void pageReinit(DbPage *pData){
MemPage *pPage;
pPage = (MemPage *)sqlite3PagerGetExtra(pData);
if( pPage->isInit ){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->isInit = 0;
if( sqlite3PagerPageRefcount(pData)>0 ){
sqlite3BtreeInitPage(pPage);
}
}
}
/*
** Invoke the busy handler for a btree.
*/
static int btreeInvokeBusyHandler(void *pArg){
BtShared *pBt = (BtShared*)pArg;
assert( pBt->db );
assert( sqlite3_mutex_held(pBt->db->mutex) );
return sqlite3InvokeBusyHandler(&pBt->db->busyHandler);
}
/*
** Open a database file.
**
** zFilename is the name of the database file. If zFilename is NULL
** a new database with a random name is created. This randomly named
** database file will be deleted when sqlite3BtreeClose() is called.
** If zFilename is ":memory:" then an in-memory database is created
** that is automatically destroyed when it is closed.
*/
int sqlite3BtreeOpen(
const char *zFilename, /* Name of the file containing the BTree database */
sqlite3 *db, /* Associated database handle */
Btree **ppBtree, /* Pointer to new Btree object written here */
int flags, /* Options */
int vfsFlags /* Flags passed through to sqlite3_vfs.xOpen() */
){
sqlite3_vfs *pVfs; /* The VFS to use for this btree */
BtShared *pBt = 0; /* Shared part of btree structure */
Btree *p; /* Handle to return */
int rc = SQLITE_OK;
int nReserve;
unsigned char zDbHeader[100];
/* Set the variable isMemdb to true for an in-memory database, or
** false for a file-based database. This symbol is only required if
** either of the shared-data or autovacuum features are compiled
** into the library.
*/
#if !defined(SQLITE_OMIT_SHARED_CACHE) || !defined(SQLITE_OMIT_AUTOVACUUM)
#ifdef SQLITE_OMIT_MEMORYDB
const int isMemdb = 0;
#else
const int isMemdb = zFilename && !strcmp(zFilename, ":memory:");
#endif
#endif
assert( db!=0 );
assert( sqlite3_mutex_held(db->mutex) );
pVfs = db->pVfs;
p = sqlite3MallocZero(sizeof(Btree));
if( !p ){
return SQLITE_NOMEM;
}
p->inTrans = TRANS_NONE;
p->db = db;
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/*
** If this Btree is a candidate for shared cache, try to find an
** existing BtShared object that we can share with
*/
if( isMemdb==0
&& (db->flags & SQLITE_Vtab)==0
&& zFilename && zFilename[0]
){
if( sqlite3GlobalConfig.sharedCacheEnabled ){
int nFullPathname = pVfs->mxPathname+1;
char *zFullPathname = sqlite3Malloc(nFullPathname);
sqlite3_mutex *mutexShared;
p->sharable = 1;
db->flags |= SQLITE_SharedCache;
if( !zFullPathname ){
sqlite3_free(p);
return SQLITE_NOMEM;
}
sqlite3OsFullPathname(pVfs, zFilename, nFullPathname, zFullPathname);
mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
sqlite3_mutex_enter(mutexShared);
for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
assert( pBt->nRef>0 );
if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager))
&& sqlite3PagerVfs(pBt->pPager)==pVfs ){
p->pBt = pBt;
pBt->nRef++;
break;
}
}
sqlite3_mutex_leave(mutexShared);
sqlite3_free(zFullPathname);
}
#ifdef SQLITE_DEBUG
else{
/* In debug mode, we mark all persistent databases as sharable
** even when they are not. This exercises the locking code and
** gives more opportunity for asserts(sqlite3_mutex_held())
** statements to find locking problems.
*/
p->sharable = 1;
}
#endif
}
#endif
if( pBt==0 ){
/*
** The following asserts make sure that structures used by the btree are
** the right size. This is to guard against size changes that result
** when compiling on a different architecture.
*/
assert( sizeof(i64)==8 || sizeof(i64)==4 );
assert( sizeof(u64)==8 || sizeof(u64)==4 );
assert( sizeof(u32)==4 );
assert( sizeof(u16)==2 );
assert( sizeof(Pgno)==4 );
pBt = sqlite3MallocZero( sizeof(*pBt) );
if( pBt==0 ){
rc = SQLITE_NOMEM;
goto btree_open_out;
}
rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
EXTRA_SIZE, flags, vfsFlags);
if( rc==SQLITE_OK ){
rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
}
if( rc!=SQLITE_OK ){
goto btree_open_out;
}
sqlite3PagerSetBusyhandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
p->pBt = pBt;
sqlite3PagerSetReiniter(pBt->pPager, pageReinit);
pBt->pCursor = 0;
pBt->pPage1 = 0;
pBt->readOnly = sqlite3PagerIsreadonly(pBt->pPager);
pBt->pageSize = get2byte(&zDbHeader[16]);
if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
|| ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
pBt->pageSize = 0;
sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the magic name ":memory:" will create an in-memory database, then
** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
** SQLITE_DEFAULT_AUTOVACUUM is true. On the other hand, if
** SQLITE_OMIT_MEMORYDB has been defined, then ":memory:" is just a
** regular file-name. In this case the auto-vacuum applies as per normal.
*/
if( zFilename && !isMemdb ){
pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
}
#endif
nReserve = 0;
}else{
nReserve = zDbHeader[20];
pBt->pageSizeFixed = 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
#endif
}
pBt->usableSize = pBt->pageSize - nReserve;
assert( (pBt->pageSize & 7)==0 ); /* 8-byte alignment of pageSize */
sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* Add the new BtShared object to the linked list sharable BtShareds.
*/
if( p->sharable ){
sqlite3_mutex *mutexShared;
pBt->nRef = 1;
mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
if( pBt->mutex==0 ){
rc = SQLITE_NOMEM;
db->mallocFailed = 0;
goto btree_open_out;
}
}
sqlite3_mutex_enter(mutexShared);
pBt->pNext = GLOBAL(BtShared*,sqlite3SharedCacheList);
GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt;
sqlite3_mutex_leave(mutexShared);
}
#endif
}
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* If the new Btree uses a sharable pBtShared, then link the new
** Btree into the list of all sharable Btrees for the same connection.
** The list is kept in ascending order by pBt address.
*/
if( p->sharable ){
int i;
Btree *pSib;
for(i=0; i<db->nDb; i++){
if( (pSib = db->aDb[i].pBt)!=0 && pSib->sharable ){
while( pSib->pPrev ){ pSib = pSib->pPrev; }
if( p->pBt<pSib->pBt ){
p->pNext = pSib;
p->pPrev = 0;
pSib->pPrev = p;
}else{
while( pSib->pNext && pSib->pNext->pBt<p->pBt ){
pSib = pSib->pNext;
}
p->pNext = pSib->pNext;
p->pPrev = pSib;
if( p->pNext ){
p->pNext->pPrev = p;
}
pSib->pNext = p;
}
break;
}
}
}
#endif
*ppBtree = p;
btree_open_out:
if( rc!=SQLITE_OK ){
if( pBt && pBt->pPager ){
sqlite3PagerClose(pBt->pPager);
}
sqlite3_free(pBt);
sqlite3_free(p);
*ppBtree = 0;
}
return rc;
}
/*
** Decrement the BtShared.nRef counter. When it reaches zero,
** remove the BtShared structure from the sharing list. Return
** true if the BtShared.nRef counter reaches zero and return
** false if it is still positive.
*/
static int removeFromSharingList(BtShared *pBt){
#ifndef SQLITE_OMIT_SHARED_CACHE
sqlite3_mutex *pMaster;
BtShared *pList;
int removed = 0;
assert( sqlite3_mutex_notheld(pBt->mutex) );
pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
sqlite3_mutex_enter(pMaster);
pBt->nRef--;
if( pBt->nRef<=0 ){
if( GLOBAL(BtShared*,sqlite3SharedCacheList)==pBt ){
GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt->pNext;
}else{
pList = GLOBAL(BtShared*,sqlite3SharedCacheList);
while( ALWAYS(pList) && pList->pNext!=pBt ){
pList=pList->pNext;
}
if( ALWAYS(pList) ){
pList->pNext = pBt->pNext;
}
}
if( SQLITE_THREADSAFE ){
sqlite3_mutex_free(pBt->mutex);
}
removed = 1;
}
sqlite3_mutex_leave(pMaster);
return removed;
#else
return 1;
#endif
}
/*
** Make sure pBt->pTmpSpace points to an allocation of
** MX_CELL_SIZE(pBt) bytes.
*/
static void allocateTempSpace(BtShared *pBt){
if( !pBt->pTmpSpace ){
pBt->pTmpSpace = sqlite3PageMalloc( pBt->pageSize );
}
}
/*
** Free the pBt->pTmpSpace allocation
*/
static void freeTempSpace(BtShared *pBt){
sqlite3PageFree( pBt->pTmpSpace);
pBt->pTmpSpace = 0;
}
/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *p){
BtShared *pBt = p->pBt;
BtCursor *pCur;
/* Close all cursors opened via this handle. */
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
pBt->db = p->db;
pCur = pBt->pCursor;
while( pCur ){
BtCursor *pTmp = pCur;
pCur = pCur->pNext;
if( pTmp->pBtree==p ){
sqlite3BtreeCloseCursor(pTmp);
}
}
/* Rollback any active transaction and free the handle structure.
** The call to sqlite3BtreeRollback() drops any table-locks held by
** this handle.
*/
sqlite3BtreeRollback(p);
sqlite3BtreeLeave(p);
/* If there are still other outstanding references to the shared-btree
** structure, return now. The remainder of this procedure cleans
** up the shared-btree.
*/
assert( p->wantToLock==0 && p->locked==0 );
if( !p->sharable || removeFromSharingList(pBt) ){
/* The pBt is no longer on the sharing list, so we can access
** it without having to hold the mutex.
**
** Clean out and delete the BtShared object.
*/
assert( !pBt->pCursor );
sqlite3PagerClose(pBt->pPager);
if( pBt->xFreeSchema && pBt->pSchema ){
pBt->xFreeSchema(pBt->pSchema);
}
sqlite3_free(pBt->pSchema);
freeTempSpace(pBt);
sqlite3_free(pBt);
}
#ifndef SQLITE_OMIT_SHARED_CACHE
assert( p->wantToLock==0 );
assert( p->locked==0 );
if( p->pPrev ) p->pPrev->pNext = p->pNext;
if( p->pNext ) p->pNext->pPrev = p->pPrev;
#endif
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Change the limit on the number of pages allowed in the cache.
**
** The maximum number of cache pages is set to the absolute
** value of mxPage. If mxPage is negative, the pager will
** operate asynchronously - it will not stop to do fsync()s
** to insure data is written to the disk surface before
** continuing. Transactions still work if synchronous is off,
** and the database cannot be corrupted if this program
** crashes. But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
*/
int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetCachesize(pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures. Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage) Level 2 is the default. There
** is a very low but non-zero probability of damage. Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite3BtreeSetSafetyLevel(Btree *p, int level, int fullSync){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetSafetyLevel(pBt->pPager, level, fullSync);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
#endif
/*
** Return TRUE if the given btree is set to safety level 1. In other
** words, return TRUE if no sync() occurs on the disk files.
*/
int sqlite3BtreeSyncDisabled(Btree *p){
BtShared *pBt = p->pBt;
int rc;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
assert( pBt && pBt->pPager );
rc = sqlite3PagerNosync(pBt->pPager);
sqlite3BtreeLeave(p);
return rc;
}
#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
/*
** Change the default pages size and the number of reserved bytes per page.
**
** The page size must be a power of 2 between 512 and 65536. If the page
** size supplied does not meet this constraint then the page size is not
** changed.
**
** Page sizes are constrained to be a power of two so that the region
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
*/
int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve){
int rc = SQLITE_OK;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( pBt->pageSizeFixed ){
sqlite3BtreeLeave(p);
return SQLITE_READONLY;
}
if( nReserve<0 ){
nReserve = pBt->pageSize - pBt->usableSize;
}
if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
((pageSize-1)&pageSize)==0 ){
assert( (pageSize & 7)==0 );
assert( !pBt->pPage1 && !pBt->pCursor );
pBt->pageSize = pageSize;
freeTempSpace(pBt);
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
}
pBt->usableSize = pBt->pageSize - nReserve;
sqlite3BtreeLeave(p);
return rc;
}
/*
** Return the currently defined page size
*/
int sqlite3BtreeGetPageSize(Btree *p){
return p->pBt->pageSize;
}
int sqlite3BtreeGetReserve(Btree *p){
int n;
sqlite3BtreeEnter(p);
n = p->pBt->pageSize - p->pBt->usableSize;
sqlite3BtreeLeave(p);
return n;
}
/*
** Set the maximum page count for a database if mxPage is positive.
** No changes are made if mxPage is 0 or negative.
** Regardless of the value of mxPage, return the maximum page count.
*/
int sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
int n;
sqlite3BtreeEnter(p);
n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return n;
}
#endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */
/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
** is disabled. The default value for the auto-vacuum property is
** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
*/
int sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
#ifdef SQLITE_OMIT_AUTOVACUUM
return SQLITE_READONLY;
#else
BtShared *pBt = p->pBt;
int rc = SQLITE_OK;
int av = (autoVacuum?1:0);
sqlite3BtreeEnter(p);
if( pBt->pageSizeFixed && av!=pBt->autoVacuum ){
rc = SQLITE_READONLY;
}else{
pBt->autoVacuum = av;
}
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** Return the value of the 'auto-vacuum' property. If auto-vacuum is
** enabled 1 is returned. Otherwise 0.
*/
int sqlite3BtreeGetAutoVacuum(Btree *p){
#ifdef SQLITE_OMIT_AUTOVACUUM
return BTREE_AUTOVACUUM_NONE;
#else
int rc;
sqlite3BtreeEnter(p);
rc = (
(!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
(!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
BTREE_AUTOVACUUM_INCR
);
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** Get a reference to pPage1 of the database file. This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success. If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked. SQLITE_NOMEM
** is returned if we run out of memory.
*/
static int lockBtree(BtShared *pBt){
int rc;
MemPage *pPage1;
int nPage;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->pPage1 ) return SQLITE_OK;
rc = sqlite3BtreeGetPage(pBt, 1, &pPage1, 0);
if( rc!=SQLITE_OK ) return rc;
/* Do some checking to help insure the file we opened really is
** a valid database file.
*/
rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
if( rc!=SQLITE_OK ){
goto page1_init_failed;
}else if( nPage>0 ){
int pageSize;
int usableSize;
u8 *page1 = pPage1->aData;
rc = SQLITE_NOTADB;
if( memcmp(page1, zMagicHeader, 16)!=0 ){
goto page1_init_failed;
}
if( page1[18]>1 ){
pBt->readOnly = 1;
}
if( page1[19]>1 ){
goto page1_init_failed;
}
/* The maximum embedded fraction must be exactly 25%. And the minimum
** embedded fraction must be 12.5% for both leaf-data and non-leaf-data.
** The original design allowed these amounts to vary, but as of
** version 3.6.0, we require them to be fixed.
*/
if( memcmp(&page1[21], "\100\040\040",3)!=0 ){
goto page1_init_failed;
}
pageSize = get2byte(&page1[16]);
if( ((pageSize-1)&pageSize)!=0 || pageSize<512 ||
(SQLITE_MAX_PAGE_SIZE<32768 && pageSize>SQLITE_MAX_PAGE_SIZE)
){
goto page1_init_failed;
}
assert( (pageSize & 7)==0 );
usableSize = pageSize - page1[20];
if( pageSize!=pBt->pageSize ){
/* After reading the first page of the database assuming a page size
** of BtShared.pageSize, we have discovered that the page-size is
** actually pageSize. Unlock the database, leave pBt->pPage1 at
** zero and return SQLITE_OK. The caller will call this function
** again with the correct page-size.
*/
releasePage(pPage1);
pBt->usableSize = usableSize;
pBt->pageSize = pageSize;
freeTempSpace(pBt);
sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
return SQLITE_OK;
}
if( usableSize<500 ){
goto page1_init_failed;
}
pBt->pageSize = pageSize;
pBt->usableSize = usableSize;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
#endif
}
/* maxLocal is the maximum amount of payload to store locally for
** a cell. Make sure it is small enough so that at least minFanout
** cells can will fit on one page. We assume a 10-byte page header.
** Besides the payload, the cell must store:
** 2-byte pointer to the cell
** 4-byte child pointer
** 9-byte nKey value
** 4-byte nData value
** 4-byte overflow page pointer
** So a cell consists of a 2-byte poiner, a header which is as much as
** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
** page pointer.
*/
pBt->maxLocal = (pBt->usableSize-12)*64/255 - 23;
pBt->minLocal = (pBt->usableSize-12)*32/255 - 23;
pBt->maxLeaf = pBt->usableSize - 35;
pBt->minLeaf = (pBt->usableSize-12)*32/255 - 23;
assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
pBt->pPage1 = pPage1;
return SQLITE_OK;
page1_init_failed:
releasePage(pPage1);
pBt->pPage1 = 0;
return rc;
}
/*
** This routine works like lockBtree() except that it also invokes the
** busy callback if there is lock contention.
*/
static int lockBtreeWithRetry(Btree *pRef){
int rc = SQLITE_OK;
assert( sqlite3BtreeHoldsMutex(pRef) );
if( pRef->inTrans==TRANS_NONE ){
u8 inTransaction = pRef->pBt->inTransaction;
btreeIntegrity(pRef);
rc = sqlite3BtreeBeginTrans(pRef, 0);
pRef->pBt->inTransaction = inTransaction;
pRef->inTrans = TRANS_NONE;
if( rc==SQLITE_OK ){
pRef->pBt->nTransaction--;
}
btreeIntegrity(pRef);
}
return rc;
}
/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which
** has the effect of releasing the read lock.
**
** If there are any outstanding cursors, this routine is a no-op.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
if( sqlite3PagerRefcount(pBt->pPager)>=1 ){
assert( pBt->pPage1->aData );
#if 0
if( pBt->pPage1->aData==0 ){
MemPage *pPage = pBt->pPage1;
pPage->aData = sqlite3PagerGetData(pPage->pDbPage);
pPage->pBt = pBt;
pPage->pgno = 1;
}
#endif
releasePage(pBt->pPage1);
}
pBt->pPage1 = 0;
pBt->inStmt = 0;
}
}
/*
** Create a new database by initializing the first page of the
** file.
*/
static int newDatabase(BtShared *pBt){
MemPage *pP1;
unsigned char *data;
int rc;
int nPage;
assert( sqlite3_mutex_held(pBt->mutex) );
rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
if( rc!=SQLITE_OK || nPage>0 ){
return rc;
}
pP1 = pBt->pPage1;
assert( pP1!=0 );
data = pP1->aData;
rc = sqlite3PagerWrite(pP1->pDbPage);
if( rc ) return rc;
memcpy(data, zMagicHeader, sizeof(zMagicHeader));
assert( sizeof(zMagicHeader)==16 );
put2byte(&data[16], pBt->pageSize);
data[18] = 1;
data[19] = 1;
data[20] = pBt->pageSize - pBt->usableSize;
data[21] = 64;
data[22] = 32;
data[23] = 32;
memset(&data[24], 0, 100-24);
zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
pBt->pageSizeFixed = 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
put4byte(&data[36 + 4*4], pBt->autoVacuum);
put4byte(&data[36 + 7*4], pBt->incrVacuum);
#endif
return SQLITE_OK;
}
/*
** Attempt to start a new transaction. A write-transaction
** is started if the second argument is nonzero, otherwise a read-
** transaction. If the second argument is 2 or more and exclusive
** transaction is started, meaning that no other process is allowed
** to access the database. A preexisting transaction may not be
** upgraded to exclusive by calling this routine a second time - the
** exclusivity flag only works for a new transaction.
**
** A write-transaction must be started before attempting any
** changes to the database. None of the following routines
** will work unless a transaction is started first:
**
** sqlite3BtreeCreateTable()
** sqlite3BtreeCreateIndex()
** sqlite3BtreeClearTable()
** sqlite3BtreeDropTable()
** sqlite3BtreeInsert()
** sqlite3BtreeDelete()
** sqlite3BtreeUpdateMeta()
**
** If an initial attempt to acquire the lock fails because of lock contention
** and the database was previously unlocked, then invoke the busy handler
** if there is one. But if there was previously a read-lock, do not
** invoke the busy handler - just return SQLITE_BUSY. SQLITE_BUSY is
** returned when there is already a read-lock in order to avoid a deadlock.
**
** Suppose there are two processes A and B. A has a read lock and B has
** a reserved lock. B tries to promote to exclusive but is blocked because
** of A's read lock. A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress. By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
BtShared *pBt = p->pBt;
int rc = SQLITE_OK;
sqlite3BtreeEnter(p);
pBt->db = p->db;
btreeIntegrity(p);
/* If the btree is already in a write-transaction, or it
** is already in a read-transaction and a read-transaction
** is requested, this is a no-op.
*/
if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
goto trans_begun;
}
/* Write transactions are not possible on a read-only database */
if( pBt->readOnly && wrflag ){
rc = SQLITE_READONLY;
goto trans_begun;
}
/* If another database handle has already opened a write transaction
** on this shared-btree structure and a second write transaction is
** requested, return SQLITE_BUSY.
*/
if( pBt->inTransaction==TRANS_WRITE && wrflag ){
rc = SQLITE_BUSY;
goto trans_begun;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
if( wrflag>1 ){
BtLock *pIter;
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->pBtree!=p ){
rc = SQLITE_BUSY;
goto trans_begun;
}
}
}
#endif
do {
if( pBt->pPage1==0 ){
do{
rc = lockBtree(pBt);
}while( pBt->pPage1==0 && rc==SQLITE_OK );
}
if( rc==SQLITE_OK && wrflag ){
if( pBt->readOnly ){
rc = SQLITE_READONLY;
}else{
rc = sqlite3PagerBegin(pBt->pPage1->pDbPage, wrflag>1);
if( rc==SQLITE_OK ){
rc = newDatabase(pBt);
}
}
}
if( rc==SQLITE_OK ){
if( wrflag ) pBt->inStmt = 0;
}else{
unlockBtreeIfUnused(pBt);
}
}while( rc==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
btreeInvokeBusyHandler(pBt) );
if( rc==SQLITE_OK ){
if( p->inTrans==TRANS_NONE ){
pBt->nTransaction++;
}
p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
if( p->inTrans>pBt->inTransaction ){
pBt->inTransaction = p->inTrans;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
if( wrflag>1 ){
assert( !pBt->pExclusive );
pBt->pExclusive = p;
}
#endif
}
trans_begun:
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Set the pointer-map entries for all children of page pPage. Also, if
** pPage contains cells that point to overflow pages, set the pointer
** map entries for the overflow pages as well.
*/
static int setChildPtrmaps(MemPage *pPage){
int i; /* Counter variable */
int nCell; /* Number of cells in page pPage */
int rc; /* Return code */
BtShared *pBt = pPage->pBt;
int isInitOrig = pPage->isInit;
Pgno pgno = pPage->pgno;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
rc = sqlite3BtreeInitPage(pPage);
if( rc!=SQLITE_OK ){
goto set_child_ptrmaps_out;
}
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
rc = ptrmapPutOvflPtr(pPage, pCell);
if( rc!=SQLITE_OK ){
goto set_child_ptrmaps_out;
}
if( !pPage->leaf ){
Pgno childPgno = get4byte(pCell);
rc = ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno);
if( rc!=SQLITE_OK ) goto set_child_ptrmaps_out;
}
}
if( !pPage->leaf ){
Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
rc = ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno);
}
set_child_ptrmaps_out:
pPage->isInit = isInitOrig;
return rc;
}
/*
** Somewhere on pPage, which is guarenteed to be a btree page, not an overflow
** page, is a pointer to page iFrom. Modify this pointer so that it points to
** iTo. Parameter eType describes the type of pointer to be modified, as
** follows:
**
** PTRMAP_BTREE: pPage is a btree-page. The pointer points at a child
** page of pPage.
**
** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
** page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
** overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
if( eType==PTRMAP_OVERFLOW2 ){
/* The pointer is always the first 4 bytes of the page in this case. */
if( get4byte(pPage->aData)!=iFrom ){
return SQLITE_CORRUPT_BKPT;
}
put4byte(pPage->aData, iTo);
}else{
int isInitOrig = pPage->isInit;
int i;
int nCell;
sqlite3BtreeInitPage(pPage);
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
if( eType==PTRMAP_OVERFLOW1 ){
CellInfo info;
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
if( info.iOverflow ){
if( iFrom==get4byte(&pCell[info.iOverflow]) ){
put4byte(&pCell[info.iOverflow], iTo);
break;
}
}
}else{
if( get4byte(pCell)==iFrom ){
put4byte(pCell, iTo);
break;
}
}
}
if( i==nCell ){
if( eType!=PTRMAP_BTREE ||
get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
return SQLITE_CORRUPT_BKPT;
}
put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
}
pPage->isInit = isInitOrig;
}
return SQLITE_OK;
}
/*
** Move the open database page pDbPage to location iFreePage in the
** database. The pDbPage reference remains valid.
*/
static int relocatePage(
BtShared *pBt, /* Btree */
MemPage *pDbPage, /* Open page to move */
u8 eType, /* Pointer map 'type' entry for pDbPage */
Pgno iPtrPage, /* Pointer map 'page-no' entry for pDbPage */
Pgno iFreePage, /* The location to move pDbPage to */
int isCommit
){
MemPage *pPtrPage; /* The page that contains a pointer to pDbPage */
Pgno iDbPage = pDbPage->pgno;
Pager *pPager = pBt->pPager;
int rc;
assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 ||
eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pDbPage->pBt==pBt );
/* Move page iDbPage from its current location to page number iFreePage */
TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n",
iDbPage, iFreePage, iPtrPage, eType));
rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage, isCommit);
if( rc!=SQLITE_OK ){
return rc;
}
pDbPage->pgno = iFreePage;
/* If pDbPage was a btree-page, then it may have child pages and/or cells
** that point to overflow pages. The pointer map entries for all these
** pages need to be changed.
**
** If pDbPage is an overflow page, then the first 4 bytes may store a
** pointer to a subsequent overflow page. If this is the case, then
** the pointer map needs to be updated for the subsequent overflow page.
*/
if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
rc = setChildPtrmaps(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
Pgno nextOvfl = get4byte(pDbPage->aData);
if( nextOvfl!=0 ){
rc = ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
/* Fix the database pointer on page iPtrPage that pointed at iDbPage so
** that it points at iFreePage. Also fix the pointer map entry for
** iPtrPage.
*/
if( eType!=PTRMAP_ROOTPAGE ){
rc = sqlite3BtreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pPtrPage->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pPtrPage);
return rc;
}
rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
releasePage(pPtrPage);
if( rc==SQLITE_OK ){
rc = ptrmapPut(pBt, iFreePage, eType, iPtrPage);
}
}
return rc;
}
/* Forward declaration required by incrVacuumStep(). */
static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
/*
** Perform a single step of an incremental-vacuum. If successful,
** return SQLITE_OK. If there is no work to do (and therefore no
** point in calling this function again), return SQLITE_DONE.
**
** More specificly, this function attempts to re-organize the
** database so that the last page of the file currently in use
** is no longer in use.
**
** If the nFin parameter is non-zero, the implementation assumes
** that the caller will keep calling incrVacuumStep() until
** it returns SQLITE_DONE or an error, and that nFin is the
** number of pages the database file will contain after this
** process is complete.
*/
static int incrVacuumStep(BtShared *pBt, Pgno nFin){
Pgno iLastPg; /* Last page in the database */
Pgno nFreeList; /* Number of pages still on the free-list */
assert( sqlite3_mutex_held(pBt->mutex) );
iLastPg = pBt->nTrunc;
if( iLastPg==0 ){
iLastPg = pagerPagecount(pBt);
}
if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
int rc;
u8 eType;
Pgno iPtrPage;
nFreeList = get4byte(&pBt->pPage1->aData[36]);
if( nFreeList==0 || nFin==iLastPg ){
return SQLITE_DONE;
}
rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
if( rc!=SQLITE_OK ){
return rc;
}
if( eType==PTRMAP_ROOTPAGE ){
return SQLITE_CORRUPT_BKPT;
}
if( eType==PTRMAP_FREEPAGE ){
if( nFin==0 ){
/* Remove the page from the files free-list. This is not required
** if nFin is non-zero. In that case, the free-list will be
** truncated to zero after this function returns, so it doesn't
** matter if it still contains some garbage entries.
*/
Pgno iFreePg;
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, 1);
if( rc!=SQLITE_OK ){
return rc;
}
assert( iFreePg==iLastPg );
releasePage(pFreePg);
}
} else {
Pgno iFreePg; /* Index of free page to move pLastPg to */
MemPage *pLastPg;
rc = sqlite3BtreeGetPage(pBt, iLastPg, &pLastPg, 0);
if( rc!=SQLITE_OK ){
return rc;
}
/* If nFin is zero, this loop runs exactly once and page pLastPg
** is swapped with the first free page pulled off the free list.
**
** On the other hand, if nFin is greater than zero, then keep
** looping until a free-page located within the first nFin pages
** of the file is found.
*/
do {
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, 0, 0);
if( rc!=SQLITE_OK ){
releasePage(pLastPg);
return rc;
}
releasePage(pFreePg);
}while( nFin!=0 && iFreePg>nFin );
assert( iFreePg<iLastPg );
rc = sqlite3PagerWrite(pLastPg->pDbPage);
if( rc==SQLITE_OK ){
rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, nFin!=0);
}
releasePage(pLastPg);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
pBt->nTrunc = iLastPg - 1;
while( pBt->nTrunc==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, pBt->nTrunc) ){
pBt->nTrunc--;
}
return SQLITE_OK;
}
/*
** A write-transaction must be opened before calling this function.
** It performs a single unit of work towards an incremental vacuum.
**
** If the incremental vacuum is finished after this function has run,
** SQLITE_DONE is returned. If it is not finished, but no error occured,
** SQLITE_OK is returned. Otherwise an SQLite error code.
*/
int sqlite3BtreeIncrVacuum(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
pBt->db = p->db;
assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
if( !pBt->autoVacuum ){
rc = SQLITE_DONE;
}else{
invalidateAllOverflowCache(pBt);
rc = incrVacuumStep(pBt, 0);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** This routine is called prior to sqlite3PagerCommit when a transaction
** is commited for an auto-vacuum database.
**
** If SQLITE_OK is returned, then *pnTrunc is set to the number of pages
** the database file should be truncated to during the commit process.
** i.e. the database has been reorganized so that only the first *pnTrunc
** pages are in use.
*/
static int autoVacuumCommit(BtShared *pBt, Pgno *pnTrunc){
int rc = SQLITE_OK;
Pager *pPager = pBt->pPager;
VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager) );
assert( sqlite3_mutex_held(pBt->mutex) );
invalidateAllOverflowCache(pBt);
assert(pBt->autoVacuum);
if( !pBt->incrVacuum ){
Pgno nFin = 0;
if( pBt->nTrunc==0 ){
Pgno nFree;
Pgno nPtrmap;
const int pgsz = pBt->pageSize;
Pgno nOrig = pagerPagecount(pBt);
if( PTRMAP_ISPAGE(pBt, nOrig) ){
return SQLITE_CORRUPT_BKPT;
}
if( nOrig==PENDING_BYTE_PAGE(pBt) ){
nOrig--;
}
nFree = get4byte(&pBt->pPage1->aData[36]);
nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+pgsz/5)/(pgsz/5);
nFin = nOrig - nFree - nPtrmap;
if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<=PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
}
while( rc==SQLITE_OK ){
rc = incrVacuumStep(pBt, nFin);
}
if( rc==SQLITE_DONE ){
assert(nFin==0 || pBt->nTrunc==0 || nFin<=pBt->nTrunc);
rc = SQLITE_OK;
if( pBt->nTrunc && nFin ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
put4byte(&pBt->pPage1->aData[32], 0);
put4byte(&pBt->pPage1->aData[36], 0);
pBt->nTrunc = nFin;
}
}
if( rc!=SQLITE_OK ){
sqlite3PagerRollback(pPager);
}
}
if( rc==SQLITE_OK ){
*pnTrunc = pBt->nTrunc;
pBt->nTrunc = 0;
}
assert( nRef==sqlite3PagerRefcount(pPager) );
return rc;
}
#endif /* ifndef SQLITE_OMIT_AUTOVACUUM */
/*
** This routine does the first phase of a two-phase commit. This routine
** causes a rollback journal to be created (if it does not already exist)
** and populated with enough information so that if a power loss occurs
** the database can be restored to its original state by playing back
** the journal. Then the contents of the journal are flushed out to
** the disk. After the journal is safely on oxide, the changes to the
** database are written into the database file and flushed to oxide.
** At the end of this call, the rollback journal still exists on the
** disk and we are still holding all locks, so the transaction has not
** committed. See sqlite3BtreeCommit() for the second phase of the
** commit process.
**
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
** individual journal file, or is NULL, indicating no master journal file
** (single database transaction).
**
** When this is called, the master journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite3BtreeCommitPhaseOne(Btree *p, const char *zMaster){
int rc = SQLITE_OK;
if( p->inTrans==TRANS_WRITE ){
BtShared *pBt = p->pBt;
Pgno nTrunc = 0;
sqlite3BtreeEnter(p);
pBt->db = p->db;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
rc = autoVacuumCommit(pBt, &nTrunc);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
}
#endif
rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zMaster, nTrunc, 0);
sqlite3BtreeLeave(p);
}
return rc;
}
/*
** Commit the transaction currently in progress.
**
** This routine implements the second phase of a 2-phase commit. The
** sqlite3BtreeSync() routine does the first phase and should be invoked
** prior to calling this routine. The sqlite3BtreeSync() routine did
** all the work of writing information out to disk and flushing the
** contents so that they are written onto the disk platter. All this
** routine has to do is delete or truncate the rollback journal
** (which causes the transaction to commit) and drop locks.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommitPhaseTwo(Btree *p){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
pBt->db = p->db;
btreeIntegrity(p);
/* If the handle has a write-transaction open, commit the shared-btrees
** transaction and set the shared state to TRANS_READ.
*/
if( p->inTrans==TRANS_WRITE ){
int rc;
assert( pBt->inTransaction==TRANS_WRITE );
assert( pBt->nTransaction>0 );
rc = sqlite3PagerCommitPhaseTwo(pBt->pPager);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
pBt->inTransaction = TRANS_READ;
pBt->inStmt = 0;
}
unlockAllTables(p);
/* If the handle has any kind of transaction open, decrement the transaction
** count of the shared btree. If the transaction count reaches 0, set
** the shared state to TRANS_NONE. The unlockBtreeIfUnused() call below
** will unlock the pager.
*/
if( p->inTrans!=TRANS_NONE ){
pBt->nTransaction--;
if( 0==pBt->nTransaction ){
pBt->inTransaction = TRANS_NONE;
}
}
/* Set the handles current transaction state to TRANS_NONE and unlock
** the pager if this call closed the only read or write transaction.
*/
p->inTrans = TRANS_NONE;
unlockBtreeIfUnused(pBt);
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Do both phases of a commit.
*/
int sqlite3BtreeCommit(Btree *p){
int rc;
sqlite3BtreeEnter(p);
rc = sqlite3BtreeCommitPhaseOne(p, 0);
if( rc==SQLITE_OK ){
rc = sqlite3BtreeCommitPhaseTwo(p);
}
sqlite3BtreeLeave(p);
return rc;
}
#ifndef NDEBUG
/*
** Return the number of write-cursors open on this handle. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
**
** For the purposes of this routine, a write-cursor is any cursor that
** is capable of writing to the databse. That means the cursor was
** originally opened for writing and the cursor has not be disabled
** by having its state changed to CURSOR_FAULT.
*/
static int countWriteCursors(BtShared *pBt){
BtCursor *pCur;
int r = 0;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->wrFlag && pCur->eState!=CURSOR_FAULT ) r++;
}
return r;
}
#endif
/*
** This routine sets the state to CURSOR_FAULT and the error
** code to errCode for every cursor on BtShared that pBtree
** references.
**
** Every cursor is tripped, including cursors that belong
** to other database connections that happen to be sharing
** the cache with pBtree.
**
** This routine gets called when a rollback occurs.
** All cursors using the same cache must be tripped
** to prevent them from trying to use the btree after
** the rollback. The rollback may have deleted tables
** or moved root pages, so it is not sufficient to
** save the state of the cursor. The cursor must be
** invalidated.
*/
void sqlite3BtreeTripAllCursors(Btree *pBtree, int errCode){
BtCursor *p;
sqlite3BtreeEnter(pBtree);
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
int i;
sqlite3BtreeClearCursor(p);
p->eState = CURSOR_FAULT;
p->skip = errCode;
for(i=0; i<=p->iPage; i++){
releasePage(p->apPage[i]);
p->apPage[i] = 0;
}
}
sqlite3BtreeLeave(pBtree);
}
/*
** Rollback the transaction in progress. All cursors will be
** invalided by this operation. Any attempt to use a cursor
** that was open at the beginning of this operation will result
** in an error.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeRollback(Btree *p){
int rc;
BtShared *pBt = p->pBt;
MemPage *pPage1;
sqlite3BtreeEnter(p);
pBt->db = p->db;
rc = saveAllCursors(pBt, 0, 0);
#ifndef SQLITE_OMIT_SHARED_CACHE
if( rc!=SQLITE_OK ){
/* This is a horrible situation. An IO or malloc() error occured whilst
** trying to save cursor positions. If this is an automatic rollback (as
** the result of a constraint, malloc() failure or IO error) then
** the cache may be internally inconsistent (not contain valid trees) so
** we cannot simply return the error to the caller. Instead, abort
** all queries that may be using any of the cursors that failed to save.
*/
sqlite3BtreeTripAllCursors(p, rc);
}
#endif
btreeIntegrity(p);
unlockAllTables(p);
if( p->inTrans==TRANS_WRITE ){
int rc2;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->nTrunc = 0;
#endif
assert( TRANS_WRITE==pBt->inTransaction );
rc2 = sqlite3PagerRollback(pBt->pPager);
if( rc2!=SQLITE_OK ){
rc = rc2;
}
/* The rollback may have destroyed the pPage1->aData value. So
** call sqlite3BtreeGetPage() on page 1 again to make
** sure pPage1->aData is set correctly. */
if( sqlite3BtreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
releasePage(pPage1);
}
assert( countWriteCursors(pBt)==0 );
pBt->inTransaction = TRANS_READ;
}
if( p->inTrans!=TRANS_NONE ){
assert( pBt->nTransaction>0 );
pBt->nTransaction--;
if( 0==pBt->nTransaction ){
pBt->inTransaction = TRANS_NONE;
}
}
p->inTrans = TRANS_NONE;
pBt->inStmt = 0;
unlockBtreeIfUnused(pBt);
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Start a statement subtransaction. The subtransaction can
** can be rolled back independently of the main transaction.
** You must start a transaction before starting a subtransaction.
** The subtransaction is ended automatically if the main transaction
** commits or rolls back.
**
** Only one subtransaction may be active at a time. It is an error to try
** to start a new subtransaction if another subtransaction is already active.
**
** Statement subtransactions are used around individual SQL statements
** that are contained within a BEGIN...COMMIT block. If a constraint
** error occurs within the statement, the effect of that one statement
** can be rolled back without having to rollback the entire transaction.
*/
int sqlite3BtreeBeginStmt(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
pBt->db = p->db;
if( (p->inTrans!=TRANS_WRITE) || pBt->inStmt ){
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}else{
assert( pBt->inTransaction==TRANS_WRITE );
rc = pBt->readOnly ? SQLITE_OK : sqlite3PagerStmtBegin(pBt->pPager);
pBt->inStmt = 1;
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Commit the statment subtransaction currently in progress. If no
** subtransaction is active, this is a no-op.
*/
int sqlite3BtreeCommitStmt(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
pBt->db = p->db;
if( pBt->inStmt && !pBt->readOnly ){
rc = sqlite3PagerStmtCommit(pBt->pPager);
}else{
rc = SQLITE_OK;
}
pBt->inStmt = 0;
sqlite3BtreeLeave(p);
return rc;
}
/*
** Rollback the active statement subtransaction. If no subtransaction
** is active this routine is a no-op.
**
** All cursors will be invalidated by this operation. Any attempt
** to use a cursor that was open at the beginning of this operation
** will result in an error.
*/
int sqlite3BtreeRollbackStmt(Btree *p){
int rc = SQLITE_OK;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
pBt->db = p->db;
if( pBt->inStmt && !pBt->readOnly ){
rc = sqlite3PagerStmtRollback(pBt->pPager);
pBt->inStmt = 0;
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Create a new cursor for the BTree whose root is on the page
** iTable. The act of acquiring a cursor gets a read lock on
** the database file.
**
** If wrFlag==0, then the cursor can only be used for reading.
** If wrFlag==1, then the cursor can be used for reading or for
** writing if other conditions for writing are also met. These
** are the conditions that must be met in order for writing to
** be allowed:
**
** 1: The cursor must have been opened with wrFlag==1
**
** 2: Other database connections that share the same pager cache
** but which are not in the READ_UNCOMMITTED state may not have
** cursors open with wrFlag==0 on the same table. Otherwise
** the changes made by this write cursor would be visible to
** the read cursors in the other database connection.
**
** 3: The database must be writable (not on read-only media)
**
** 4: There must be an active transaction.
**
** No checking is done to make sure that page iTable really is the
** root page of a b-tree. If it is not, then the cursor acquired
** will not work correctly.
**
** It is assumed that the sqlite3BtreeCursorSize() bytes of memory
** pointed to by pCur have been zeroed by the caller.
*/
static int btreeCursor(
Btree *p, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
struct KeyInfo *pKeyInfo, /* First arg to comparison function */
BtCursor *pCur /* Space for new cursor */
){
int rc;
Pgno nPage;
BtShared *pBt = p->pBt;
assert( sqlite3BtreeHoldsMutex(p) );
if( wrFlag ){
if( pBt->readOnly ){
return SQLITE_READONLY;
}
if( checkReadLocks(p, iTable, 0, 0) ){
return SQLITE_LOCKED;
}
}
if( pBt->pPage1==0 ){
rc = lockBtreeWithRetry(p);
if( rc!=SQLITE_OK ){
return rc;
}
if( pBt->readOnly && wrFlag ){
return SQLITE_READONLY;
}
}
pCur->pgnoRoot = (Pgno)iTable;
rc = sqlite3PagerPagecount(pBt->pPager, (int *)&nPage);
if( rc!=SQLITE_OK ){
return rc;
}
if( iTable==1 && nPage==0 ){
rc = SQLITE_EMPTY;
goto create_cursor_exception;
}
rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]);
if( rc!=SQLITE_OK ){
goto create_cursor_exception;
}
/* Now that no other errors can occur, finish filling in the BtCursor
** variables, link the cursor into the BtShared list and set *ppCur (the
** output argument to this function).
*/
pCur->pKeyInfo = pKeyInfo;
pCur->pBtree = p;
pCur->pBt = pBt;
pCur->wrFlag = wrFlag;
pCur->pNext = pBt->pCursor;
if( pCur->pNext ){
pCur->pNext->pPrev = pCur;
}
pBt->pCursor = pCur;
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
create_cursor_exception:
releasePage(pCur->apPage[0]);
unlockBtreeIfUnused(pBt);
return rc;
}
int sqlite3BtreeCursor(
Btree *p, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
struct KeyInfo *pKeyInfo, /* First arg to xCompare() */
BtCursor *pCur /* Write new cursor here */
){
int rc;
sqlite3BtreeEnter(p);
p->pBt->db = p->db;
rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
sqlite3BtreeLeave(p);
return rc;
}
int sqlite3BtreeCursorSize(){
return sizeof(BtCursor);
}
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
Btree *pBtree = pCur->pBtree;
if( pBtree ){
int i;
BtShared *pBt = pCur->pBt;
sqlite3BtreeEnter(pBtree);
pBt->db = pBtree->db;
sqlite3BtreeClearCursor(pCur);
if( pCur->pPrev ){
pCur->pPrev->pNext = pCur->pNext;
}else{
pBt->pCursor = pCur->pNext;
}
if( pCur->pNext ){
pCur->pNext->pPrev = pCur->pPrev;
}
for(i=0; i<=pCur->iPage; i++){
releasePage(pCur->apPage[i]);
}
unlockBtreeIfUnused(pBt);
invalidateOverflowCache(pCur);
/* sqlite3_free(pCur); */
sqlite3BtreeLeave(pBtree);
}
return SQLITE_OK;
}
/*
** Make a temporary cursor by filling in the fields of pTempCur.
** The temporary cursor is not on the cursor list for the Btree.
*/
void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur){
int i;
assert( cursorHoldsMutex(pCur) );
memcpy(pTempCur, pCur, sizeof(BtCursor));
pTempCur->pNext = 0;
pTempCur->pPrev = 0;
for(i=0; i<=pTempCur->iPage; i++){
sqlite3PagerRef(pTempCur->apPage[i]->pDbPage);
}
assert( pTempCur->pKey==0 );
}
/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
void sqlite3BtreeReleaseTempCursor(BtCursor *pCur){
int i;
assert( cursorHoldsMutex(pCur) );
for(i=0; i<=pCur->iPage; i++){
sqlite3PagerUnref(pCur->apPage[i]->pDbPage);
}
sqlite3_free(pCur->pKey);
}
/*
** Make sure the BtCursor* given in the argument has a valid
** BtCursor.info structure. If it is not already valid, call
** sqlite3BtreeParseCell() to fill it in.
**
** BtCursor.info is a cache of the information in the current cell.
** Using this cache reduces the number of calls to sqlite3BtreeParseCell().
**
** 2007-06-25: There is a bug in some versions of MSVC that cause the
** compiler to crash when getCellInfo() is implemented as a macro.
** But there is a measureable speed advantage to using the macro on gcc
** (when less compiler optimizations like -Os or -O0 are used and the
** compiler is not doing agressive inlining.) So we use a real function
** for MSVC and a macro for everything else. Ticket #2457.
*/
#ifndef NDEBUG
static void assertCellInfo(BtCursor *pCur){
CellInfo info;
int iPage = pCur->iPage;
memset(&info, 0, sizeof(info));
sqlite3BtreeParseCell(pCur->apPage[iPage], pCur->aiIdx[iPage], &info);
assert( memcmp(&info, &pCur->info, sizeof(info))==0 );
}
#else
#define assertCellInfo(x)
#endif
#ifdef _MSC_VER
/* Use a real function in MSVC to work around bugs in that compiler. */
static void getCellInfo(BtCursor *pCur){
if( pCur->info.nSize==0 ){
int iPage = pCur->iPage;
sqlite3BtreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);
pCur->validNKey = 1;
}else{
assertCellInfo(pCur);
}
}
#else /* if not _MSC_VER */
/* Use a macro in all other compilers so that the function is inlined */
#define getCellInfo(pCur) \
if( pCur->info.nSize==0 ){ \
int iPage = pCur->iPage; \
sqlite3BtreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info); \
pCur->validNKey = 1; \
}else{ \
assertCellInfo(pCur); \
}
#endif /* _MSC_VER */
/*
** Set *pSize to the size of the buffer needed to hold the value of
** the key for the current entry. If the cursor is not pointing
** to a valid entry, *pSize is set to 0.
**
** For a table with the INTKEY flag set, this routine returns the key
** itself, not the number of bytes in the key.
*/
int sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = restoreCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
if( pCur->eState==CURSOR_INVALID ){
*pSize = 0;
}else{
getCellInfo(pCur);
*pSize = pCur->info.nKey;
}
}
return rc;
}
/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to. Always return SQLITE_OK.
** Failure is not possible. If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = restoreCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
if( pCur->eState==CURSOR_INVALID ){
/* Not pointing at a valid entry - set *pSize to 0. */
*pSize = 0;
}else{
getCellInfo(pCur);
*pSize = pCur->info.nData;
}
}
return rc;
}
/*
** Given the page number of an overflow page in the database (parameter
** ovfl), this function finds the page number of the next page in the
** linked list of overflow pages. If possible, it uses the auto-vacuum
** pointer-map data instead of reading the content of page ovfl to do so.
**
** If an error occurs an SQLite error code is returned. Otherwise:
**
** Unless pPgnoNext is NULL, the page number of the next overflow
** page in the linked list is written to *pPgnoNext. If page ovfl
** is the last page in its linked list, *pPgnoNext is set to zero.
**
** If ppPage is not NULL, *ppPage is set to the MemPage* handle
** for page ovfl. The underlying pager page may have been requested
** with the noContent flag set, so the page data accessable via
** this handle may not be trusted.
*/
static int getOverflowPage(
BtShared *pBt,
Pgno ovfl, /* Overflow page */
MemPage **ppPage, /* OUT: MemPage handle */
Pgno *pPgnoNext /* OUT: Next overflow page number */
){
Pgno next = 0;
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
/* One of these must not be NULL. Otherwise, why call this function? */
assert(ppPage || pPgnoNext);
/* If pPgnoNext is NULL, then this function is being called to obtain
** a MemPage* reference only. No page-data is required in this case.
*/
if( !pPgnoNext ){
return sqlite3BtreeGetPage(pBt, ovfl, ppPage, 1);
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/* Try to find the next page in the overflow list using the
** autovacuum pointer-map pages. Guess that the next page in
** the overflow list is page number (ovfl+1). If that guess turns
** out to be wrong, fall back to loading the data of page
** number ovfl to determine the next page number.
*/
if( pBt->autoVacuum ){
Pgno pgno;
Pgno iGuess = ovfl+1;
u8 eType;
while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
iGuess++;
}
if( iGuess<=pagerPagecount(pBt) ){
rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
if( rc!=SQLITE_OK ){
return rc;
}
if( eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
next = iGuess;
}
}
}
#endif
if( next==0 || ppPage ){
MemPage *pPage = 0;
rc = sqlite3BtreeGetPage(pBt, ovfl, &pPage, next!=0);
assert(rc==SQLITE_OK || pPage==0);
if( next==0 && rc==SQLITE_OK ){
next = get4byte(pPage->aData);
}
if( ppPage ){
*ppPage = pPage;
}else{
releasePage(pPage);
}
}
*pPgnoNext = next;
return rc;
}
/*
** Copy data from a buffer to a page, or from a page to a buffer.
**
** pPayload is a pointer to data stored on database page pDbPage.
** If argument eOp is false, then nByte bytes of data are copied
** from pPayload to the buffer pointed at by pBuf. If eOp is true,
** then sqlite3PagerWrite() is called on pDbPage and nByte bytes
** of data are copied from the buffer pBuf to pPayload.
**
** SQLITE_OK is returned on success, otherwise an error code.
*/
static int copyPayload(
void *pPayload, /* Pointer to page data */
void *pBuf, /* Pointer to buffer */
int nByte, /* Number of bytes to copy */
int eOp, /* 0 -> copy from page, 1 -> copy to page */
DbPage *pDbPage /* Page containing pPayload */
){
if( eOp ){
/* Copy data from buffer to page (a write operation) */
int rc = sqlite3PagerWrite(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
memcpy(pPayload, pBuf, nByte);
}else{
/* Copy data from page to buffer (a read operation) */
memcpy(pBuf, pPayload, nByte);
}
return SQLITE_OK;
}
/*
** This function is used to read or overwrite payload information
** for the entry that the pCur cursor is pointing to. If the eOp
** parameter is 0, this is a read operation (data copied into
** buffer pBuf). If it is non-zero, a write (data copied from
** buffer pBuf).
**
** A total of "amt" bytes are read or written beginning at "offset".
** Data is read to or from the buffer pBuf.
**
** This routine does not make a distinction between key and data.
** It just reads or writes bytes from the payload area. Data might
** appear on the main page or be scattered out on multiple overflow
** pages.
**
** If the BtCursor.isIncrblobHandle flag is set, and the current
** cursor entry uses one or more overflow pages, this function
** allocates space for and lazily popluates the overflow page-list
** cache array (BtCursor.aOverflow). Subsequent calls use this
** cache to make seeking to the supplied offset more efficient.
**
** Once an overflow page-list cache has been allocated, it may be
** invalidated if some other cursor writes to the same table, or if
** the cursor is moved to a different row. Additionally, in auto-vacuum
** mode, the following events may invalidate an overflow page-list cache.
**
** * An incremental vacuum,
** * A commit in auto_vacuum="full" mode,
** * Creating a table (may require moving an overflow page).
*/
static int accessPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
u32 offset, /* Begin reading this far into payload */
u32 amt, /* Read this many bytes */
unsigned char *pBuf, /* Write the bytes into this buffer */
int skipKey, /* offset begins at data if this is true */
int eOp /* zero to read. non-zero to write. */
){
unsigned char *aPayload;
int rc = SQLITE_OK;
u32 nKey;
int iIdx = 0;
MemPage *pPage = pCur->apPage[pCur->iPage]; /* Btree page of current entry */
BtShared *pBt = pCur->pBt; /* Btree this cursor belongs to */
assert( pPage );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
assert( cursorHoldsMutex(pCur) );
getCellInfo(pCur);
aPayload = pCur->info.pCell + pCur->info.nHeader;
nKey = (pPage->intKey ? 0 : pCur->info.nKey);
if( skipKey ){
offset += nKey;
}
if( offset+amt > nKey+pCur->info.nData
|| &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
){
/* Trying to read or write past the end of the data is an error */
return SQLITE_CORRUPT_BKPT;
}
/* Check if data must be read/written to/from the btree page itself. */
if( offset<pCur->info.nLocal ){
int a = amt;
if( a+offset>pCur->info.nLocal ){
a = pCur->info.nLocal - offset;
}
rc = copyPayload(&aPayload[offset], pBuf, a, eOp, pPage->pDbPage);
offset = 0;
pBuf += a;
amt -= a;
}else{
offset -= pCur->info.nLocal;
}
if( rc==SQLITE_OK && amt>0 ){
const u32 ovflSize = pBt->usableSize - 4; /* Bytes content per ovfl page */
Pgno nextPage;
nextPage = get4byte(&aPayload[pCur->info.nLocal]);
#ifndef SQLITE_OMIT_INCRBLOB
/* If the isIncrblobHandle flag is set and the BtCursor.aOverflow[]
** has not been allocated, allocate it now. The array is sized at
** one entry for each overflow page in the overflow chain. The
** page number of the first overflow page is stored in aOverflow[0],
** etc. A value of 0 in the aOverflow[] array means "not yet known"
** (the cache is lazily populated).
*/
if( pCur->isIncrblobHandle && !pCur->aOverflow ){
int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
pCur->aOverflow = (Pgno *)sqlite3MallocZero(sizeof(Pgno)*nOvfl);
if( nOvfl && !pCur->aOverflow ){
rc = SQLITE_NOMEM;
}
}
/* If the overflow page-list cache has been allocated and the
** entry for the first required overflow page is valid, skip
** directly to it.
*/
if( pCur->aOverflow && pCur->aOverflow[offset/ovflSize] ){
iIdx = (offset/ovflSize);
nextPage = pCur->aOverflow[iIdx];
offset = (offset%ovflSize);
}
#endif
for( ; rc==SQLITE_OK && amt>0 && nextPage; iIdx++){
#ifndef SQLITE_OMIT_INCRBLOB
/* If required, populate the overflow page-list cache. */
if( pCur->aOverflow ){
assert(!pCur->aOverflow[iIdx] || pCur->aOverflow[iIdx]==nextPage);
pCur->aOverflow[iIdx] = nextPage;
}
#endif
if( offset>=ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. The page
** data is not required. So first try to lookup the overflow
** page-list cache, if any, then fall back to the getOverflowPage()
** function.
*/
#ifndef SQLITE_OMIT_INCRBLOB
if( pCur->aOverflow && pCur->aOverflow[iIdx+1] ){
nextPage = pCur->aOverflow[iIdx+1];
} else
#endif
rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
offset -= ovflSize;
}else{
/* Need to read this page properly. It contains some of the
** range of data that is being read (eOp==0) or written (eOp!=0).
*/
DbPage *pDbPage;
int a = amt;
rc = sqlite3PagerGet(pBt->pPager, nextPage, &pDbPage);
if( rc==SQLITE_OK ){
aPayload = sqlite3PagerGetData(pDbPage);
nextPage = get4byte(aPayload);
if( a + offset > ovflSize ){
a = ovflSize - offset;
}
rc = copyPayload(&aPayload[offset+4], pBuf, a, eOp, pDbPage);
sqlite3PagerUnref(pDbPage);
offset = 0;
amt -= a;
pBuf += a;
}
}
}
}
if( rc==SQLITE_OK && amt>0 ){
return SQLITE_CORRUPT_BKPT;
}
return rc;
}
/*
** Read part of the key associated with cursor pCur. Exactly
** "amt" bytes will be transfered into pBuf[]. The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
int rc;
assert( cursorHoldsMutex(pCur) );
rc = restoreCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
if( pCur->apPage[0]->intKey ){
return SQLITE_CORRUPT_BKPT;
}
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
rc = accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0, 0);
}
return rc;
}
/*
** Read part of the data associated with cursor pCur. Exactly
** "amt" bytes will be transfered into pBuf[]. The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
int rc;
#ifndef SQLITE_OMIT_INCRBLOB
if ( pCur->eState==CURSOR_INVALID ){
return SQLITE_ABORT;
}
#endif
assert( cursorHoldsMutex(pCur) );
rc = restoreCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
rc = accessPayload(pCur, offset, amt, pBuf, 1, 0);
}
return rc;
}
/*
** Return a pointer to payload information from the entry that the
** pCur cursor is pointing to. The pointer is to the beginning of
** the key if skipKey==0 and it points to the beginning of data if
** skipKey==1. The number of bytes of available key/data is written
** into *pAmt. If *pAmt==0, then the value returned will not be
** a valid pointer.
**
** This routine is an optimization. It is common for the entire key
** and data to fit on the local page and for there to be no overflow
** pages. When that is so, this routine can be used to access the
** key and data without making a copy. If the key and/or data spills
** onto overflow pages, then accessPayload() must be used to reassembly
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached
** page of the database. The data might change or move the next time
** any btree routine is called.
*/
static const unsigned char *fetchPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
int *pAmt, /* Write the number of available bytes here */
int skipKey /* read beginning at data if this is true */
){
unsigned char *aPayload;
MemPage *pPage;
u32 nKey;
u32 nLocal;
assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
assert( pCur->eState==CURSOR_VALID );
assert( cursorHoldsMutex(pCur) );
pPage = pCur->apPage[pCur->iPage];
assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
getCellInfo(pCur);
aPayload = pCur->info.pCell;
aPayload += pCur->info.nHeader;
if( pPage->intKey ){
nKey = 0;
}else{
nKey = pCur->info.nKey;
}
if( skipKey ){
aPayload += nKey;
nLocal = pCur->info.nLocal - nKey;
}else{
nLocal = pCur->info.nLocal;
if( nLocal>nKey ){
nLocal = nKey;
}
}
*pAmt = nLocal;
return aPayload;
}
/*
** For the entry that cursor pCur is point to, return as
** many bytes of the key or data as are available on the local
** b-tree page. Write the number of available bytes into *pAmt.
**
** The pointer returned is ephemeral. The key/data may move
** or be destroyed on the next call to any Btree routine,
** including calls from other threads against the same cache.
** Hence, a mutex on the BtShared should be held prior to calling
** this routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
*/
const void *sqlite3BtreeKeyFetch(BtCursor *pCur, int *pAmt){
assert( cursorHoldsMutex(pCur) );
if( pCur->eState==CURSOR_VALID ){
return (const void*)fetchPayload(pCur, pAmt, 0);
}
return 0;
}
const void *sqlite3BtreeDataFetch(BtCursor *pCur, int *pAmt){
assert( cursorHoldsMutex(pCur) );
if( pCur->eState==CURSOR_VALID ){
return (const void*)fetchPayload(pCur, pAmt, 1);
}
return 0;
}
/*
** Move the cursor down to a new child page. The newPgno argument is the
** page number of the child page to move to.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
int rc;
int i = pCur->iPage;
MemPage *pNewPage;
BtShared *pBt = pCur->pBt;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getAndInitPage(pBt, newPgno, &pNewPage);
if( rc ) return rc;
pCur->apPage[i+1] = pNewPage;
pCur->aiIdx[i+1] = 0;
pCur->iPage++;
pCur->info.nSize = 0;
pCur->validNKey = 0;
if( pNewPage->nCell<1 ){
return SQLITE_CORRUPT_BKPT;
}
return SQLITE_OK;
}
#ifndef NDEBUG
/*
** Page pParent is an internal (non-leaf) tree page. This function
** asserts that page number iChild is the left-child if the iIdx'th
** cell in page pParent. Or, if iIdx is equal to the total number of
** cells in pParent, that page number iChild is the right-child of
** the page.
*/
static void assertParentIndex(MemPage *pParent, int iIdx, Pgno iChild){
assert( iIdx<=pParent->nCell );
if( iIdx==pParent->nCell ){
assert( get4byte(&pParent->aData[pParent->hdrOffset+8])==iChild );
}else{
assert( get4byte(findCell(pParent, iIdx))==iChild );
}
}
#else
# define assertParentIndex(x,y,z)
#endif
/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from. If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
void sqlite3BtreeMoveToParent(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>0 );
assert( pCur->apPage[pCur->iPage] );
assertParentIndex(
pCur->apPage[pCur->iPage-1],
pCur->aiIdx[pCur->iPage-1],
pCur->apPage[pCur->iPage]->pgno
);
releasePage(pCur->apPage[pCur->iPage]);
pCur->iPage--;
pCur->info.nSize = 0;
pCur->validNKey = 0;
}
/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
MemPage *pRoot;
int rc = SQLITE_OK;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
assert( cursorHoldsMutex(pCur) );
assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
assert( CURSOR_VALID < CURSOR_REQUIRESEEK );
assert( CURSOR_FAULT > CURSOR_REQUIRESEEK );
if( pCur->eState>=CURSOR_REQUIRESEEK ){
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
sqlite3BtreeClearCursor(pCur);
}
if( pCur->iPage>=0 ){
int i;
for(i=1; i<=pCur->iPage; i++){
releasePage(pCur->apPage[i]);
}
}else{
if(
SQLITE_OK!=(rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]))
){
pCur->eState = CURSOR_INVALID;
return rc;
}
}
pRoot = pCur->apPage[0];
assert( pRoot->pgno==pCur->pgnoRoot );
pCur->iPage = 0;
pCur->aiIdx[0] = 0;
pCur->info.nSize = 0;
pCur->atLast = 0;
pCur->validNKey = 0;
if( pRoot->nCell==0 && !pRoot->leaf ){
Pgno subpage;
assert( pRoot->pgno==1 );
subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
assert( subpage>0 );
pCur->eState = CURSOR_VALID;
rc = moveToChild(pCur, subpage);
}else{
pCur->eState = ((pRoot->nCell>0)?CURSOR_VALID:CURSOR_INVALID);
}
return rc;
}
/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
**
** The left-most leaf is the one with the smallest key - the first
** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
pgno = get4byte(findCell(pPage, pCur->aiIdx[pCur->iPage]));
rc = moveToChild(pCur, pgno);
}
return rc;
}
/*
** Move the cursor down to the right-most leaf entry beneath the
** page to which it is currently pointing. Notice the difference
** between moveToLeftmost() and moveToRightmost(). moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
**
** The right-most entry is the one with the largest key - the last
** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
pCur->aiIdx[pCur->iPage] = pPage->nCell;
rc = moveToChild(pCur, pgno);
}
if( rc==SQLITE_OK ){
pCur->aiIdx[pCur->iPage] = pPage->nCell-1;
pCur->info.nSize = 0;
pCur->validNKey = 0;
}
return rc;
}
/* Move the cursor to the first entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
if( pCur->eState==CURSOR_INVALID ){
assert( pCur->apPage[pCur->iPage]->nCell==0 );
*pRes = 1;
rc = SQLITE_OK;
}else{
assert( pCur->apPage[pCur->iPage]->nCell>0 );
*pRes = 0;
rc = moveToLeftmost(pCur);
}
}
return rc;
}
/* Move the cursor to the last entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
if( CURSOR_INVALID==pCur->eState ){
assert( pCur->apPage[pCur->iPage]->nCell==0 );
*pRes = 1;
}else{
assert( pCur->eState==CURSOR_VALID );
*pRes = 0;
rc = moveToRightmost(pCur);
getCellInfo(pCur);
pCur->atLast = rc==SQLITE_OK;
}
}
return rc;
}
/* Move the cursor so that it points to an entry near the key
** specified by pIdxKey or intKey. Return a success code.
**
** For INTKEY tables, the intKey parameter is used. pIdxKey
** must be NULL. For index tables, pIdxKey is used and intKey
** is ignored.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present. The cursor might point to an entry that comes
** before or after the key.
**
** The result of comparing the key with the entry to which the
** cursor is written to *pRes if pRes!=NULL. The meaning of
** this value is as follows:
**
** *pRes<0 The cursor is left pointing at an entry that
** is smaller than pKey or if the table is empty
** and the cursor is therefore left point to nothing.
**
** *pRes==0 The cursor is left pointing at an entry that
** exactly matches pKey.
**
** *pRes>0 The cursor is left pointing at an entry that
** is larger than pKey.
**
*/
int sqlite3BtreeMovetoUnpacked(
BtCursor *pCur, /* The cursor to be moved */
UnpackedRecord *pIdxKey, /* Unpacked index key */
i64 intKey, /* The table key */
int biasRight, /* If true, bias the search to the high end */
int *pRes /* Write search results here */
){
int rc;
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
/* If the cursor is already positioned at the point we are trying
** to move to, then just return without doing any work */
if( pCur->eState==CURSOR_VALID && pCur->validNKey
&& pCur->apPage[0]->intKey
){
if( pCur->info.nKey==intKey ){
*pRes = 0;
return SQLITE_OK;
}
if( pCur->atLast && pCur->info.nKey<intKey ){
*pRes = -1;
return SQLITE_OK;
}
}
rc = moveToRoot(pCur);
if( rc ){
return rc;
}
assert( pCur->apPage[pCur->iPage] );
assert( pCur->apPage[pCur->iPage]->isInit );
if( pCur->eState==CURSOR_INVALID ){
*pRes = -1;
assert( pCur->apPage[pCur->iPage]->nCell==0 );
return SQLITE_OK;
}
assert( pCur->apPage[0]->intKey || pIdxKey );
for(;;){
int lwr, upr;
Pgno chldPg;
MemPage *pPage = pCur->apPage[pCur->iPage];
int c = -1; /* pRes return if table is empty must be -1 */
lwr = 0;
upr = pPage->nCell-1;
if( !pPage->intKey && pIdxKey==0 ){
rc = SQLITE_CORRUPT_BKPT;
goto moveto_finish;
}
if( biasRight ){
pCur->aiIdx[pCur->iPage] = upr;
}else{
pCur->aiIdx[pCur->iPage] = (upr+lwr)/2;
}
if( lwr<=upr ) for(;;){
void *pCellKey;
i64 nCellKey;
int idx = pCur->aiIdx[pCur->iPage];
pCur->info.nSize = 0;
pCur->validNKey = 1;
if( pPage->intKey ){
u8 *pCell;
pCell = findCell(pPage, idx) + pPage->childPtrSize;
if( pPage->hasData ){
u32 dummy;
pCell += getVarint32(pCell, dummy);
}
getVarint(pCell, (u64*)&nCellKey);
if( nCellKey==intKey ){
c = 0;
}else if( nCellKey<intKey ){
c = -1;
}else{
assert( nCellKey>intKey );
c = +1;
}
}else{
int available;
pCellKey = (void *)fetchPayload(pCur, &available, 0);
nCellKey = pCur->info.nKey;
if( available>=nCellKey ){
c = sqlite3VdbeRecordCompare(nCellKey, pCellKey, pIdxKey);
}else{
pCellKey = sqlite3Malloc( nCellKey );
if( pCellKey==0 ){
rc = SQLITE_NOMEM;
goto moveto_finish;
}
rc = sqlite3BtreeKey(pCur, 0, nCellKey, (void *)pCellKey);
c = sqlite3VdbeRecordCompare(nCellKey, pCellKey, pIdxKey);
sqlite3_free(pCellKey);
if( rc ) goto moveto_finish;
}
}
if( c==0 ){
pCur->info.nKey = nCellKey;
if( pPage->intKey && !pPage->leaf ){
lwr = idx;
upr = lwr - 1;
break;
}else{
if( pRes ) *pRes = 0;
rc = SQLITE_OK;
goto moveto_finish;
}
}
if( c<0 ){
lwr = idx+1;
}else{
upr = idx-1;
}
if( lwr>upr ){
pCur->info.nKey = nCellKey;
break;
}
pCur->aiIdx[pCur->iPage] = (lwr+upr)/2;
}
assert( lwr==upr+1 );
assert( pPage->isInit );
if( pPage->leaf ){
chldPg = 0;
}else if( lwr>=pPage->nCell ){
chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
}else{
chldPg = get4byte(findCell(pPage, lwr));
}
if( chldPg==0 ){
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
if( pRes ) *pRes = c;
rc = SQLITE_OK;
goto moveto_finish;
}
pCur->aiIdx[pCur->iPage] = lwr;
pCur->info.nSize = 0;
pCur->validNKey = 0;
rc = moveToChild(pCur, chldPg);
if( rc ) goto moveto_finish;
}
moveto_finish:
return rc;
}
/*
** In this version of BtreeMoveto, pKey is a packed index record
** such as is generated by the OP_MakeRecord opcode. Unpack the
** record and then call BtreeMovetoUnpacked() to do the work.
*/
int sqlite3BtreeMoveto(
BtCursor *pCur, /* Cursor open on the btree to be searched */
const void *pKey, /* Packed key if the btree is an index */
i64 nKey, /* Integer key for tables. Size of pKey for indices */
int bias, /* Bias search to the high end */
int *pRes /* Write search results here */
){
int rc; /* Status code */
UnpackedRecord *pIdxKey; /* Unpacked index key */
UnpackedRecord aSpace[16]; /* Temp space for pIdxKey - to avoid a malloc */
if( pKey ){
pIdxKey = sqlite3VdbeRecordUnpack(pCur->pKeyInfo, nKey, pKey,
aSpace, sizeof(aSpace));
if( pIdxKey==0 ) return SQLITE_NOMEM;
}else{
pIdxKey = 0;
}
rc = sqlite3BtreeMovetoUnpacked(pCur, pIdxKey, nKey, bias, pRes);
if( pKey ){
sqlite3VdbeDeleteUnpackedRecord(pIdxKey);
}
return rc;
}
/*
** Return TRUE if the cursor is not pointing at an entry of the table.
**
** TRUE will be returned after a call to sqlite3BtreeNext() moves
** past the last entry in the table or sqlite3BtreePrev() moves past
** the first entry. TRUE is also returned if the table is empty.
*/
int sqlite3BtreeEof(BtCursor *pCur){
/* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
** have been deleted? This API will need to change to return an error code
** as well as the boolean result value.
*/
return (CURSOR_VALID!=pCur->eState);
}
/*
** Return the database connection handle for a cursor.
*/
sqlite3 *sqlite3BtreeCursorDb(const BtCursor *pCur){
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
return pCur->pBtree->db;
}
/*
** Advance the cursor to the next entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.
*/
int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
int rc;
int idx;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
rc = restoreCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pRes!=0 );
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
if( pCur->skip>0 ){
pCur->skip = 0;
*pRes = 0;
return SQLITE_OK;
}
pCur->skip = 0;
pPage = pCur->apPage[pCur->iPage];
idx = ++pCur->aiIdx[pCur->iPage];
assert( pPage->isInit );
assert( idx<=pPage->nCell );
pCur->info.nSize = 0;
pCur->validNKey = 0;
if( idx>=pPage->nCell ){
if( !pPage->leaf ){
rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
if( rc ) return rc;
rc = moveToLeftmost(pCur);
*pRes = 0;
return rc;
}
do{
if( pCur->iPage==0 ){
*pRes = 1;
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
}
sqlite3BtreeMoveToParent(pCur);
pPage = pCur->apPage[pCur->iPage];
}while( pCur->aiIdx[pCur->iPage]>=pPage->nCell );
*pRes = 0;
if( pPage->intKey ){
rc = sqlite3BtreeNext(pCur, pRes);
}else{
rc = SQLITE_OK;
}
return rc;
}
*pRes = 0;
if( pPage->leaf ){
return SQLITE_OK;
}
rc = moveToLeftmost(pCur);
return rc;
}
/*
** Step the cursor to the back to the previous entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.
*/
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
int rc;
MemPage *pPage;
assert( cursorHoldsMutex(pCur) );
rc = restoreCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
pCur->atLast = 0;
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
if( pCur->skip<0 ){
pCur->skip = 0;
*pRes = 0;
return SQLITE_OK;
}
pCur->skip = 0;
pPage = pCur->apPage[pCur->iPage];
assert( pPage->isInit );
if( !pPage->leaf ){
int idx = pCur->aiIdx[pCur->iPage];
rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
if( rc ){
return rc;
}
rc = moveToRightmost(pCur);
}else{
while( pCur->aiIdx[pCur->iPage]==0 ){
if( pCur->iPage==0 ){
pCur->eState = CURSOR_INVALID;
*pRes = 1;
return SQLITE_OK;
}
sqlite3BtreeMoveToParent(pCur);
}
pCur->info.nSize = 0;
pCur->validNKey = 0;
pCur->aiIdx[pCur->iPage]--;
pPage = pCur->apPage[pCur->iPage];
if( pPage->intKey && !pPage->leaf ){
rc = sqlite3BtreePrevious(pCur, pRes);
}else{
rc = SQLITE_OK;
}
}
*pRes = 0;
return rc;
}
/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty. (In other words, sqlite3PagerWrite()
** has already been called on the new page.) The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite3PagerUnref() on the new page when it is done.
**
** SQLITE_OK is returned on success. Any other return value indicates
** an error. *ppPage and *pPgno are undefined in the event of an error.
** Do not invoke sqlite3PagerUnref() on *ppPage if an error is returned.
**
** If the "nearby" parameter is not 0, then a (feeble) effort is made to
** locate a page close to the page number "nearby". This can be used in an
** attempt to keep related pages close to each other in the database file,
** which in turn can make database access faster.
**
** If the "exact" parameter is not 0, and the page-number nearby exists
** anywhere on the free-list, then it is guarenteed to be returned. This
** is only used by auto-vacuum databases when allocating a new table.
*/
static int allocateBtreePage(
BtShared *pBt,
MemPage **ppPage,
Pgno *pPgno,
Pgno nearby,
u8 exact
){
MemPage *pPage1;
int rc;
int n; /* Number of pages on the freelist */
int k; /* Number of leaves on the trunk of the freelist */
MemPage *pTrunk = 0;
MemPage *pPrevTrunk = 0;
assert( sqlite3_mutex_held(pBt->mutex) );
pPage1 = pBt->pPage1;
n = get4byte(&pPage1->aData[36]);
if( n>0 ){
/* There are pages on the freelist. Reuse one of those pages. */
Pgno iTrunk;
u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
/* If the 'exact' parameter was true and a query of the pointer-map
** shows that the page 'nearby' is somewhere on the free-list, then
** the entire-list will be searched for that page.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
if( exact && nearby<=pagerPagecount(pBt) ){
u8 eType;
assert( nearby>0 );
assert( pBt->autoVacuum );
rc = ptrmapGet(pBt, nearby, &eType, 0);
if( rc ) return rc;
if( eType==PTRMAP_FREEPAGE ){
searchList = 1;
}
*pPgno = nearby;
}
#endif
/* Decrement the free-list count by 1. Set iTrunk to the index of the
** first free-list trunk page. iPrevTrunk is initially 1.
*/
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) return rc;
put4byte(&pPage1->aData[36], n-1);
/* The code within this loop is run only once if the 'searchList' variable
** is not true. Otherwise, it runs once for each trunk-page on the
** free-list until the page 'nearby' is located.
*/
do {
pPrevTrunk = pTrunk;
if( pPrevTrunk ){
iTrunk = get4byte(&pPrevTrunk->aData[0]);
}else{
iTrunk = get4byte(&pPage1->aData[32]);
}
rc = sqlite3BtreeGetPage(pBt, iTrunk, &pTrunk, 0);
if( rc ){
pTrunk = 0;
goto end_allocate_page;
}
k = get4byte(&pTrunk->aData[4]);
if( k==0 && !searchList ){
/* The trunk has no leaves and the list is not being searched.
** So extract the trunk page itself and use it as the newly
** allocated page */
assert( pPrevTrunk==0 );
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
*pPgno = iTrunk;
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
*ppPage = pTrunk;
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
}else if( k>pBt->usableSize/4 - 2 ){
/* Value of k is out of range. Database corruption */
rc = SQLITE_CORRUPT_BKPT;
goto end_allocate_page;
#ifndef SQLITE_OMIT_AUTOVACUUM
}else if( searchList && nearby==iTrunk ){
/* The list is being searched and this trunk page is the page
** to allocate, regardless of whether it has leaves.
*/
assert( *pPgno==iTrunk );
*ppPage = pTrunk;
searchList = 0;
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
if( k==0 ){
if( !pPrevTrunk ){
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
}else{
memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
}
}else{
/* The trunk page is required by the caller but it contains
** pointers to free-list leaves. The first leaf becomes a trunk
** page in this case.
*/
MemPage *pNewTrunk;
Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
rc = sqlite3BtreeGetPage(pBt, iNewTrunk, &pNewTrunk, 0);
if( rc!=SQLITE_OK ){
goto end_allocate_page;
}
rc = sqlite3PagerWrite(pNewTrunk->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pNewTrunk);
goto end_allocate_page;
}
memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
put4byte(&pNewTrunk->aData[4], k-1);
memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
releasePage(pNewTrunk);
if( !pPrevTrunk ){
assert( sqlite3PagerIswriteable(pPage1->pDbPage) );
put4byte(&pPage1->aData[32], iNewTrunk);
}else{
rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
put4byte(&pPrevTrunk->aData[0], iNewTrunk);
}
}
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
#endif
}else{
/* Extract a leaf from the trunk */
int closest;
Pgno iPage;
unsigned char *aData = pTrunk->aData;
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
if( nearby>0 ){
int i, dist;
closest = 0;
dist = get4byte(&aData[8]) - nearby;
if( dist<0 ) dist = -dist;
for(i=1; i<k; i++){
int d2 = get4byte(&aData[8+i*4]) - nearby;
if( d2<0 ) d2 = -d2;
if( d2<dist ){
closest = i;
dist = d2;
}
}
}else{
closest = 0;
}
iPage = get4byte(&aData[8+closest*4]);
if( !searchList || iPage==nearby ){
Pgno nPage;
*pPgno = iPage;
nPage = pagerPagecount(pBt);
if( *pPgno>nPage ){
/* Free page off the end of the file */
rc = SQLITE_CORRUPT_BKPT;
goto end_allocate_page;
}
TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
": %d more free pages\n",
*pPgno, closest+1, k, pTrunk->pgno, n-1));
if( closest<k-1 ){
memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
}
put4byte(&aData[4], k-1);
assert( sqlite3PagerIswriteable(pTrunk->pDbPage) );
rc = sqlite3BtreeGetPage(pBt, *pPgno, ppPage, 1);
if( rc==SQLITE_OK ){
sqlite3PagerDontRollback((*ppPage)->pDbPage);
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
}
}
searchList = 0;
}
}
releasePage(pPrevTrunk);
pPrevTrunk = 0;
}while( searchList );
}else{
/* There are no pages on the freelist, so create a new page at the
** end of the file */
int nPage = pagerPagecount(pBt);
*pPgno = nPage + 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->nTrunc ){
/* An incr-vacuum has already run within this transaction. So the
** page to allocate is not from the physical end of the file, but
** at pBt->nTrunc.
*/
*pPgno = pBt->nTrunc+1;
if( *pPgno==PENDING_BYTE_PAGE(pBt) ){
(*pPgno)++;
}
}
if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, *pPgno) ){
/* If *pPgno refers to a pointer-map page, allocate two new pages
** at the end of the file instead of one. The first allocated page
** becomes a new pointer-map page, the second is used by the caller.
*/
TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", *pPgno));
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
(*pPgno)++;
if( *pPgno==PENDING_BYTE_PAGE(pBt) ){ (*pPgno)++; }
}
if( pBt->nTrunc ){
pBt->nTrunc = *pPgno;
}
#endif
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
rc = sqlite3BtreeGetPage(pBt, *pPgno, ppPage, 0);
if( rc ) return rc;
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
}
TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
}
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
end_allocate_page:
releasePage(pTrunk);
releasePage(pPrevTrunk);
if( rc==SQLITE_OK ){
if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
releasePage(*ppPage);
return SQLITE_CORRUPT_BKPT;
}
(*ppPage)->isInit = 0;
}
return rc;
}
/*
** Add a page of the database file to the freelist.
**
** sqlite3PagerUnref() is NOT called for pPage.
*/
static int freePage(MemPage *pPage){
BtShared *pBt = pPage->pBt;
MemPage *pPage1 = pBt->pPage1;
int rc, n, k;
/* Prepare the page for freeing */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->pgno>1 );
pPage->isInit = 0;
/* Increment the free page count on pPage1 */
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) return rc;
n = get4byte(&pPage1->aData[36]);
put4byte(&pPage1->aData[36], n+1);
#ifdef SQLITE_SECURE_DELETE
/* If the SQLITE_SECURE_DELETE compile-time option is enabled, then
** always fully overwrite deleted information with zeros.
*/
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
memset(pPage->aData, 0, pPage->pBt->pageSize);
#endif
/* If the database supports auto-vacuum, write an entry in the pointer-map
** to indicate that the page is free.
*/
if( ISAUTOVACUUM ){
rc = ptrmapPut(pBt, pPage->pgno, PTRMAP_FREEPAGE, 0);
if( rc ) return rc;
}
if( n==0 ){
/* This is the first free page */
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
memset(pPage->aData, 0, 8);
put4byte(&pPage1->aData[32], pPage->pgno);
TRACE(("FREE-PAGE: %d first\n", pPage->pgno));
}else{
/* Other free pages already exist. Retrive the first trunk page
** of the freelist and find out how many leaves it has. */
MemPage *pTrunk;
rc = sqlite3BtreeGetPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk, 0);
if( rc ) return rc;
k = get4byte(&pTrunk->aData[4]);
if( k>=pBt->usableSize/4 - 8 ){
/* The trunk is full. Turn the page being freed into a new
** trunk page with no leaves.
**
** Note that the trunk page is not really full until it contains
** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
** coded. But due to a coding error in versions of SQLite prior to
** 3.6.0, databases with freelist trunk pages holding more than
** usableSize/4 - 8 entries will be reported as corrupt. In order
** to maintain backwards compatibility with older versions of SQLite,
** we will contain to restrict the number of entries to usableSize/4 - 8
** for now. At some point in the future (once everyone has upgraded
** to 3.6.0 or later) we should consider fixing the conditional above
** to read "usableSize/4-2" instead of "usableSize/4-8".
*/
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc==SQLITE_OK ){
put4byte(pPage->aData, pTrunk->pgno);
put4byte(&pPage->aData[4], 0);
put4byte(&pPage1->aData[32], pPage->pgno);
TRACE(("FREE-PAGE: %d new trunk page replacing %d\n",
pPage->pgno, pTrunk->pgno));
}
}else if( k<0 ){
rc = SQLITE_CORRUPT;
}else{
/* Add the newly freed page as a leaf on the current trunk */
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pTrunk->aData[4], k+1);
put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
#ifndef SQLITE_SECURE_DELETE
rc = sqlite3PagerDontWrite(pPage->pDbPage);
#endif
}
TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
}
releasePage(pTrunk);
}
return rc;
}
/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
BtShared *pBt = pPage->pBt;
CellInfo info;
Pgno ovflPgno;
int rc;
int nOvfl;
int ovflPageSize;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
if( info.iOverflow==0 ){
return SQLITE_OK; /* No overflow pages. Return without doing anything */
}
ovflPgno = get4byte(&pCell[info.iOverflow]);
ovflPageSize = pBt->usableSize - 4;
nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
assert( ovflPgno==0 || nOvfl>0 );
while( nOvfl-- ){
MemPage *pOvfl;
if( ovflPgno==0 || ovflPgno>pagerPagecount(pBt) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getOverflowPage(pBt, ovflPgno, &pOvfl, (nOvfl==0)?0:&ovflPgno);
if( rc ) return rc;
rc = freePage(pOvfl);
sqlite3PagerUnref(pOvfl->pDbPage);
if( rc ) return rc;
}
return SQLITE_OK;
}
/*
** Create the byte sequence used to represent a cell on page pPage
** and write that byte sequence into pCell[]. Overflow pages are
** allocated and filled in as necessary. The calling procedure
** is responsible for making sure sufficient space has been allocated
** for pCell[].
**
** Note that pCell does not necessary need to point to the pPage->aData
** area. pCell might point to some temporary storage. The cell will
** be constructed in this temporary area then copied into pPage->aData
** later.
*/
static int fillInCell(
MemPage *pPage, /* The page that contains the cell */
unsigned char *pCell, /* Complete text of the cell */
const void *pKey, i64 nKey, /* The key */
const void *pData,int nData, /* The data */
int nZero, /* Extra zero bytes to append to pData */
int *pnSize /* Write cell size here */
){
int nPayload;
const u8 *pSrc;
int nSrc, n, rc;
int spaceLeft;
MemPage *pOvfl = 0;
MemPage *pToRelease = 0;
unsigned char *pPrior;
unsigned char *pPayload;
BtShared *pBt = pPage->pBt;
Pgno pgnoOvfl = 0;
int nHeader;
CellInfo info;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/* pPage is not necessarily writeable since pCell might be auxiliary
** buffer space that is separate from the pPage buffer area */
assert( pCell<pPage->aData || pCell>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
/* Fill in the header. */
nHeader = 0;
if( !pPage->leaf ){
nHeader += 4;
}
if( pPage->hasData ){
nHeader += putVarint(&pCell[nHeader], nData+nZero);
}else{
nData = nZero = 0;
}
nHeader += putVarint(&pCell[nHeader], *(u64*)&nKey);
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
assert( info.nHeader==nHeader );
assert( info.nKey==nKey );
assert( info.nData==(u32)(nData+nZero) );
/* Fill in the payload */
nPayload = nData + nZero;
if( pPage->intKey ){
pSrc = pData;
nSrc = nData;
nData = 0;
}else{
nPayload += nKey;
pSrc = pKey;
nSrc = nKey;
}
*pnSize = info.nSize;
spaceLeft = info.nLocal;
pPayload = &pCell[nHeader];
pPrior = &pCell[info.iOverflow];
while( nPayload>0 ){
if( spaceLeft==0 ){
int isExact = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
if( pBt->autoVacuum ){
do{
pgnoOvfl++;
} while(
PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt)
);
if( pgnoOvfl>1 ){
/* isExact = 1; */
}
}
#endif
rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, isExact);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the database supports auto-vacuum, and the second or subsequent
** overflow page is being allocated, add an entry to the pointer-map
** for that page now.
**
** If this is the first overflow page, then write a partial entry
** to the pointer-map. If we write nothing to this pointer-map slot,
** then the optimistic overflow chain processing in clearCell()
** may misinterpret the uninitialised values and delete the
** wrong pages from the database.
*/
if( pBt->autoVacuum && rc==SQLITE_OK ){
u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
rc = ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap);
if( rc ){
releasePage(pOvfl);
}
}
#endif
if( rc ){
releasePage(pToRelease);
return rc;
}
/* If pToRelease is not zero than pPrior points into the data area
** of pToRelease. Make sure pToRelease is still writeable. */
assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
/* If pPrior is part of the data area of pPage, then make sure pPage
** is still writeable */
assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
put4byte(pPrior, pgnoOvfl);
releasePage(pToRelease);
pToRelease = pOvfl;
pPrior = pOvfl->aData;
put4byte(pPrior, 0);
pPayload = &pOvfl->aData[4];
spaceLeft = pBt->usableSize - 4;
}
n = nPayload;
if( n>spaceLeft ) n = spaceLeft;
/* If pToRelease is not zero than pPayload points into the data area
** of pToRelease. Make sure pToRelease is still writeable. */
assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
/* If pPayload is part of the data area of pPage, then make sure pPage
** is still writeable */
assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
if( nSrc>0 ){
if( n>nSrc ) n = nSrc;
assert( pSrc );
memcpy(pPayload, pSrc, n);
}else{
memset(pPayload, 0, n);
}
nPayload -= n;
pPayload += n;
pSrc += n;
nSrc -= n;
spaceLeft -= n;
if( nSrc==0 ){
nSrc = nData;
pSrc = pData;
}
}
releasePage(pToRelease);
return SQLITE_OK;
}
/*
** Remove the i-th cell from pPage. This routine effects pPage only.
** The cell content is not freed or deallocated. It is assumed that
** the cell content has been copied someplace else. This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
*/
static int dropCell(MemPage *pPage, int idx, int sz){
int i; /* Loop counter */
int pc; /* Offset to cell content of cell being deleted */
u8 *data; /* pPage->aData */
u8 *ptr; /* Used to move bytes around within data[] */
int rc; /* The return code */
assert( idx>=0 && idx<pPage->nCell );
assert( sz==cellSize(pPage, idx) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
data = pPage->aData;
ptr = &data[pPage->cellOffset + 2*idx];
pc = get2byte(ptr);
if( (pc<pPage->hdrOffset+6+(pPage->leaf?0:4))
|| (pc+sz>pPage->pBt->usableSize) ){
return SQLITE_CORRUPT_BKPT;
}
rc = freeSpace(pPage, pc, sz);
if( rc!=SQLITE_OK ){
return rc;
}
for(i=idx+1; i<pPage->nCell; i++, ptr+=2){
ptr[0] = ptr[2];
ptr[1] = ptr[3];
}
pPage->nCell--;
put2byte(&data[pPage->hdrOffset+3], pPage->nCell);
pPage->nFree += 2;
return SQLITE_OK;
}
/*
** Insert a new cell on pPage at cell index "i". pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there. If it
** will not fit, then make a copy of the cell content into pTemp if
** pTemp is not null. Regardless of pTemp, allocate a new entry
** in pPage->aOvfl[] and make it point to the cell content (either
** in pTemp or the original pCell) and also record its index.
** Allocating a new entry in pPage->aCell[] implies that
** pPage->nOverflow is incremented.
**
** If nSkip is non-zero, then do not copy the first nSkip bytes of the
** cell. The caller will overwrite them after this function returns. If
** nSkip is non-zero, then pCell may not point to an invalid memory location
** (but pCell+nSkip is always valid).
*/
static int insertCell(
MemPage *pPage, /* Page into which we are copying */
int i, /* New cell becomes the i-th cell of the page */
u8 *pCell, /* Content of the new cell */
int sz, /* Bytes of content in pCell */
u8 *pTemp, /* Temp storage space for pCell, if needed */
u8 nSkip /* Do not write the first nSkip bytes of the cell */
){
int idx; /* Where to write new cell content in data[] */
int j; /* Loop counter */
int top; /* First byte of content for any cell in data[] */
int end; /* First byte past the last cell pointer in data[] */
int ins; /* Index in data[] where new cell pointer is inserted */
int hdr; /* Offset into data[] of the page header */
int cellOffset; /* Address of first cell pointer in data[] */
u8 *data; /* The content of the whole page */
u8 *ptr; /* Used for moving information around in data[] */
assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
assert( sz==cellSizePtr(pPage, pCell) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( pPage->nOverflow || sz+2>pPage->nFree ){
if( pTemp ){
memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
pCell = pTemp;
}
j = pPage->nOverflow++;
assert( j<(int)(sizeof(pPage->aOvfl)/sizeof(pPage->aOvfl[0])) );
pPage->aOvfl[j].pCell = pCell;
pPage->aOvfl[j].idx = i;
pPage->nFree = 0;
}else{
int rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
data = pPage->aData;
hdr = pPage->hdrOffset;
top = get2byte(&data[hdr+5]);
cellOffset = pPage->cellOffset;
end = cellOffset + 2*pPage->nCell + 2;
ins = cellOffset + 2*i;
if( end > top - sz ){
rc = defragmentPage(pPage);
if( rc!=SQLITE_OK ){
return rc;
}
top = get2byte(&data[hdr+5]);
assert( end + sz <= top );
}
idx = allocateSpace(pPage, sz);
assert( idx>0 );
assert( end <= get2byte(&data[hdr+5]) );
if (idx+sz > pPage->pBt->usableSize) {
return SQLITE_CORRUPT_BKPT;
}
pPage->nCell++;
pPage->nFree -= 2;
memcpy(&data[idx+nSkip], pCell+nSkip, sz-nSkip);
for(j=end-2, ptr=&data[j]; j>ins; j-=2, ptr-=2){
ptr[0] = ptr[-2];
ptr[1] = ptr[-1];
}
put2byte(&data[ins], idx);
put2byte(&data[hdr+3], pPage->nCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pPage->pBt->autoVacuum ){
/* The cell may contain a pointer to an overflow page. If so, write
** the entry for the overflow page into the pointer map.
*/
CellInfo info;
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
if( (info.nData+(pPage->intKey?0:info.nKey))>info.nLocal ){
Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
rc = ptrmapPut(pPage->pBt, pgnoOvfl, PTRMAP_OVERFLOW1, pPage->pgno);
if( rc!=SQLITE_OK ) return rc;
}
}
#endif
}
return SQLITE_OK;
}
/*
** Add a list of cells to a page. The page should be initially empty.
** The cells are guaranteed to fit on the page.
*/
static void assemblePage(
MemPage *pPage, /* The page to be assemblied */
int nCell, /* The number of cells to add to this page */
u8 **apCell, /* Pointers to cell bodies */
u16 *aSize /* Sizes of the cells */
){
int i; /* Loop counter */
int totalSize; /* Total size of all cells */
int hdr; /* Index of page header */
int cellptr; /* Address of next cell pointer */
int cellbody; /* Address of next cell body */
u8 *data; /* Data for the page */
assert( pPage->nOverflow==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
totalSize = 0;
for(i=0; i<nCell; i++){
totalSize += aSize[i];
}
assert( totalSize+2*nCell<=pPage->nFree );
assert( pPage->nCell==0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
cellptr = pPage->cellOffset;
data = pPage->aData;
hdr = pPage->hdrOffset;
put2byte(&data[hdr+3], nCell);
if( nCell ){
cellbody = allocateSpace(pPage, totalSize);
assert( cellbody>0 );
assert( pPage->nFree >= 2*nCell );
pPage->nFree -= 2*nCell;
for(i=0; i<nCell; i++){
put2byte(&data[cellptr], cellbody);
memcpy(&data[cellbody], apCell[i], aSize[i]);
cellptr += 2;
cellbody += aSize[i];
}
assert( cellbody==pPage->pBt->usableSize );
}
pPage->nCell = nCell;
}
/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation. NN is the number of neighbors on either side
** of the page that participate in the balancing operation. NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
** The minimum value of NN is 1 (of course). Increasing NN above 1
** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
** in exchange for a larger degradation in INSERT and UPDATE performance.
** The value of NN appears to give the best results overall.
*/
#define NN 1 /* Number of neighbors on either side of pPage */
#define NB (NN*2+1) /* Total pages involved in the balance */
/* Forward reference */
static int balance(BtCursor*, int);
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** This version of balance() handles the common special case where
** a new entry is being inserted on the extreme right-end of the
** tree, in other words, when the new entry will become the largest
** entry in the tree.
**
** Instead of trying balance the 3 right-most leaf pages, just add
** a new page to the right-hand side and put the one new entry in
** that page. This leaves the right side of the tree somewhat
** unbalanced. But odds are that we will be inserting new entries
** at the end soon afterwards so the nearly empty page will quickly
** fill up. On average.
**
** pPage is the leaf page which is the right-most page in the tree.
** pParent is its parent. pPage must have a single overflow entry
** which is also the right-most entry on the page.
*/
static int balance_quick(BtCursor *pCur){
int rc;
MemPage *pNew = 0;
Pgno pgnoNew;
u8 *pCell;
u16 szCell;
CellInfo info;
MemPage *pPage = pCur->apPage[pCur->iPage];
MemPage *pParent = pCur->apPage[pCur->iPage-1];
BtShared *pBt = pPage->pBt;
int parentIdx = pParent->nCell; /* pParent new divider cell index */
int parentSize; /* Size of new divider cell */
u8 parentCell[64]; /* Space for the new divider cell */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/* Allocate a new page. Insert the overflow cell from pPage
** into it. Then remove the overflow cell from pPage.
*/
rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
if( rc==SQLITE_OK ){
pCell = pPage->aOvfl[0].pCell;
szCell = cellSizePtr(pPage, pCell);
assert( sqlite3PagerIswriteable(pNew->pDbPage) );
zeroPage(pNew, pPage->aData[0]);
assemblePage(pNew, 1, &pCell, &szCell);
pPage->nOverflow = 0;
/* pPage is currently the right-child of pParent. Change this
** so that the right-child is the new page allocated above and
** pPage is the next-to-right child.
**
** Ignore the return value of the call to fillInCell(). fillInCell()
** may only return other than SQLITE_OK if it is required to allocate
** one or more overflow pages. Since an internal table B-Tree cell
** may never spill over onto an overflow page (it is a maximum of
** 13 bytes in size), it is not neccessary to check the return code.
**
** Similarly, the insertCell() function cannot fail if the page
** being inserted into is already writable and the cell does not
** contain an overflow pointer. So ignore this return code too.
*/
assert( pPage->nCell>0 );
pCell = findCell(pPage, pPage->nCell-1);
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
fillInCell(pParent, parentCell, 0, info.nKey, 0, 0, 0, &parentSize);
assert( parentSize<64 );
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
insertCell(pParent, parentIdx, parentCell, parentSize, 0, 4);
put4byte(findOverflowCell(pParent,parentIdx), pPage->pgno);
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
/* If this is an auto-vacuum database, update the pointer map
** with entries for the new page, and any pointer from the
** cell on the page to an overflow page.
*/
if( ISAUTOVACUUM ){
rc = ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno);
if( rc==SQLITE_OK ){
rc = ptrmapPutOvfl(pNew, 0);
}
}
/* Release the reference to the new page. */
releasePage(pNew);
}
/* At this point the pPage->nFree variable is not set correctly with
** respect to the content of the page (because it was set to 0 by
** insertCell). So call sqlite3BtreeInitPage() to make sure it is
** correct.
**
** This has to be done even if an error will be returned. Normally, if
** an error occurs during tree balancing, the contents of MemPage are
** not important, as they will be recalculated when the page is rolled
** back. But here, in balance_quick(), it is possible that pPage has
** not yet been marked dirty or written into the journal file. Therefore
** it will not be rolled back and so it is important to make sure that
** the page data and contents of MemPage are consistent.
*/
pPage->isInit = 0;
sqlite3BtreeInitPage(pPage);
/* If everything else succeeded, balance the parent page, in
** case the divider cell inserted caused it to become overfull.
*/
if( rc==SQLITE_OK ){
releasePage(pPage);
pCur->iPage--;
rc = balance(pCur, 0);
}
return rc;
}
#endif /* SQLITE_OMIT_QUICKBALANCE */
/*
** This routine redistributes Cells on pPage and up to NN*2 siblings
** of pPage so that all pages have about the same amount of free space.
** Usually NN siblings on either side of pPage is used in the balancing,
** though more siblings might come from one side if pPage is the first
** or last child of its parent. If pPage has fewer than 2*NN siblings
** (something which can only happen if pPage is the root page or a
** child of root) then all available siblings participate in the balancing.
**
** The number of siblings of pPage might be increased or decreased by one or
** two in an effort to keep pages nearly full but not over full. The root page
** is special and is allowed to be nearly empty. If pPage is
** the root page, then the depth of the tree might be increased
** or decreased by one, as necessary, to keep the root page from being
** overfull or completely empty.
**
** Note that when this routine is called, some of the Cells on pPage
** might not actually be stored in pPage->aData[]. This can happen
** if the page is overfull. Part of the job of this routine is to
** make sure all Cells for pPage once again fit in pPage->aData[].
**
** In the course of balancing the siblings of pPage, the parent of pPage
** might become overfull or underfull. If that happens, then this routine
** is called recursively on the parent.
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
*/
static int balance_nonroot(BtCursor *pCur){
MemPage *pPage; /* The over or underfull page to balance */
MemPage *pParent; /* The parent of pPage */
BtShared *pBt; /* The whole database */
int nCell = 0; /* Number of cells in apCell[] */
int nMaxCells = 0; /* Allocated size of apCell, szCell, aFrom. */
int nOld; /* Number of pages in apOld[] */
int nNew; /* Number of pages in apNew[] */
int nDiv; /* Number of cells in apDiv[] */
int i, j, k; /* Loop counters */
int idx; /* Index of pPage in pParent->aCell[] */
int nxDiv; /* Next divider slot in pParent->aCell[] */
int rc; /* The return code */
int leafCorrection; /* 4 if pPage is a leaf. 0 if not */
int leafData; /* True if pPage is a leaf of a LEAFDATA tree */
int usableSpace; /* Bytes in pPage beyond the header */
int pageFlags; /* Value of pPage->aData[0] */
int subtotal; /* Subtotal of bytes in cells on one page */
int iSpace1 = 0; /* First unused byte of aSpace1[] */
int iSpace2 = 0; /* First unused byte of aSpace2[] */
int szScratch; /* Size of scratch memory requested */
MemPage *apOld[NB]; /* pPage and up to two siblings */
Pgno pgnoOld[NB]; /* Page numbers for each page in apOld[] */
MemPage *apCopy[NB]; /* Private copies of apOld[] pages */
MemPage *apNew[NB+2]; /* pPage and up to NB siblings after balancing */
Pgno pgnoNew[NB+2]; /* Page numbers for each page in apNew[] */
u8 *apDiv[NB]; /* Divider cells in pParent */
int cntNew[NB+2]; /* Index in aCell[] of cell after i-th page */
int szNew[NB+2]; /* Combined size of cells place on i-th page */
u8 **apCell = 0; /* All cells begin balanced */
u16 *szCell; /* Local size of all cells in apCell[] */
u8 *aCopy[NB]; /* Space for holding data of apCopy[] */
u8 *aSpace1; /* Space for copies of dividers cells before balance */
u8 *aSpace2 = 0; /* Space for overflow dividers cells after balance */
u8 *aFrom = 0;
pPage = pCur->apPage[pCur->iPage];
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
VVA_ONLY( pCur->pagesShuffled = 1 );
/*
** Find the parent page.
*/
assert( pCur->iPage>0 );
assert( pPage->isInit );
assert( sqlite3PagerIswriteable(pPage->pDbPage) || pPage->nOverflow==1 );
pBt = pPage->pBt;
pParent = pCur->apPage[pCur->iPage-1];
assert( pParent );
if( SQLITE_OK!=(rc = sqlite3PagerWrite(pParent->pDbPage)) ){
return rc;
}
TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** A special case: If a new entry has just been inserted into a
** table (that is, a btree with integer keys and all data at the leaves)
** and the new entry is the right-most entry in the tree (it has the
** largest key) then use the special balance_quick() routine for
** balancing. balance_quick() is much faster and results in a tighter
** packing of data in the common case.
*/
if( pPage->leaf &&
pPage->intKey &&
pPage->nOverflow==1 &&
pPage->aOvfl[0].idx==pPage->nCell &&
pParent->pgno!=1 &&
get4byte(&pParent->aData[pParent->hdrOffset+8])==pPage->pgno
){
assert( pPage->intKey );
/*
** TODO: Check the siblings to the left of pPage. It may be that
** they are not full and no new page is required.
*/
return balance_quick(pCur);
}
#endif
if( SQLITE_OK!=(rc = sqlite3PagerWrite(pPage->pDbPage)) ){
return rc;
}
/*
** Find the cell in the parent page whose left child points back
** to pPage. The "idx" variable is the index of that cell. If pPage
** is the rightmost child of pParent then set idx to pParent->nCell
*/
idx = pCur->aiIdx[pCur->iPage-1];
assertParentIndex(pParent, idx, pPage->pgno);
/*
** Initialize variables so that it will be safe to jump
** directly to balance_cleanup at any moment.
*/
nOld = nNew = 0;
/*
** Find sibling pages to pPage and the cells in pParent that divide
** the siblings. An attempt is made to find NN siblings on either
** side of pPage. More siblings are taken from one side, however, if
** pPage there are fewer than NN siblings on the other side. If pParent
** has NB or fewer children then all children of pParent are taken.
*/
nxDiv = idx - NN;
if( nxDiv + NB > pParent->nCell ){
nxDiv = pParent->nCell - NB + 1;
}
if( nxDiv<0 ){
nxDiv = 0;
}
nDiv = 0;
for(i=0, k=nxDiv; i<NB; i++, k++){
if( k<pParent->nCell ){
apDiv[i] = findCell(pParent, k);
nDiv++;
assert( !pParent->leaf );
pgnoOld[i] = get4byte(apDiv[i]);
}else if( k==pParent->nCell ){
pgnoOld[i] = get4byte(&pParent->aData[pParent->hdrOffset+8]);
}else{
break;
}
rc = getAndInitPage(pBt, pgnoOld[i], &apOld[i]);
if( rc ) goto balance_cleanup;
/* apOld[i]->idxParent = k; */
apCopy[i] = 0;
assert( i==nOld );
nOld++;
nMaxCells += 1+apOld[i]->nCell+apOld[i]->nOverflow;
}
/* Make nMaxCells a multiple of 4 in order to preserve 8-byte
** alignment */
nMaxCells = (nMaxCells + 3)&~3;
/*
** Allocate space for memory structures
*/
szScratch =
nMaxCells*sizeof(u8*) /* apCell */
+ nMaxCells*sizeof(u16) /* szCell */
+ (ROUND8(sizeof(MemPage))+pBt->pageSize)*NB /* aCopy */
+ pBt->pageSize /* aSpace1 */
+ (ISAUTOVACUUM ? nMaxCells : 0); /* aFrom */
apCell = sqlite3ScratchMalloc( szScratch );
if( apCell==0 ){
rc = SQLITE_NOMEM;
goto balance_cleanup;
}
szCell = (u16*)&apCell[nMaxCells];
aCopy[0] = (u8*)&szCell[nMaxCells];
assert( ((aCopy[0] - (u8*)apCell) & 7)==0 ); /* 8-byte alignment required */
for(i=1; i<NB; i++){
aCopy[i] = &aCopy[i-1][pBt->pageSize+ROUND8(sizeof(MemPage))];
assert( ((aCopy[i] - (u8*)apCell) & 7)==0 ); /* 8-byte alignment required */
}
aSpace1 = &aCopy[NB-1][pBt->pageSize+ROUND8(sizeof(MemPage))];
assert( ((aSpace1 - (u8*)apCell) & 7)==0 ); /* 8-byte alignment required */
if( ISAUTOVACUUM ){
aFrom = &aSpace1[pBt->pageSize];
}
aSpace2 = sqlite3PageMalloc(pBt->pageSize);
if( aSpace2==0 ){
rc = SQLITE_NOMEM;
goto balance_cleanup;
}
/*
** Make copies of the content of pPage and its siblings into aOld[].
** The rest of this function will use data from the copies rather
** that the original pages since the original pages will be in the
** process of being overwritten.
*/
for(i=0; i<nOld; i++){
MemPage *p = apCopy[i] = (MemPage*)aCopy[i];
memcpy(p, apOld[i], sizeof(MemPage));
p->aData = (void*)&p[1];
memcpy(p->aData, apOld[i]->aData, pBt->pageSize);
}
/*
** Load pointers to all cells on sibling pages and the divider cells
** into the local apCell[] array. Make copies of the divider cells
** into space obtained form aSpace1[] and remove the the divider Cells
** from pParent.
**
** If the siblings are on leaf pages, then the child pointers of the
** divider cells are stripped from the cells before they are copied
** into aSpace1[]. In this way, all cells in apCell[] are without
** child pointers. If siblings are not leaves, then all cell in
** apCell[] include child pointers. Either way, all cells in apCell[]
** are alike.
**
** leafCorrection: 4 if pPage is a leaf. 0 if pPage is not a leaf.
** leafData: 1 if pPage holds key+data and pParent holds only keys.
*/
nCell = 0;
leafCorrection = pPage->leaf*4;
leafData = pPage->hasData;
for(i=0; i<nOld; i++){
MemPage *pOld = apCopy[i];
int limit = pOld->nCell+pOld->nOverflow;
for(j=0; j<limit; j++){
assert( nCell<nMaxCells );
apCell[nCell] = findOverflowCell(pOld, j);
szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
if( ISAUTOVACUUM ){
int a;
aFrom[nCell] = i;
for(a=0; a<pOld->nOverflow; a++){
if( pOld->aOvfl[a].pCell==apCell[nCell] ){
aFrom[nCell] = 0xFF;
break;
}
}
}
nCell++;
}
if( i<nOld-1 ){
u16 sz = cellSizePtr(pParent, apDiv[i]);
if( leafData ){
/* With the LEAFDATA flag, pParent cells hold only INTKEYs that
** are duplicates of keys on the child pages. We need to remove
** the divider cells from pParent, but the dividers cells are not
** added to apCell[] because they are duplicates of child cells.
*/
dropCell(pParent, nxDiv, sz);
}else{
u8 *pTemp;
assert( nCell<nMaxCells );
szCell[nCell] = sz;
pTemp = &aSpace1[iSpace1];
iSpace1 += sz;
assert( sz<=pBt->pageSize/4 );
assert( iSpace1<=pBt->pageSize );
memcpy(pTemp, apDiv[i], sz);
apCell[nCell] = pTemp+leafCorrection;
if( ISAUTOVACUUM ){
aFrom[nCell] = 0xFF;
}
dropCell(pParent, nxDiv, sz);
szCell[nCell] -= leafCorrection;
assert( get4byte(pTemp)==pgnoOld[i] );
if( !pOld->leaf ){
assert( leafCorrection==0 );
/* The right pointer of the child page pOld becomes the left
** pointer of the divider cell */
memcpy(apCell[nCell], &pOld->aData[pOld->hdrOffset+8], 4);
}else{
assert( leafCorrection==4 );
if( szCell[nCell]<4 ){
/* Do not allow any cells smaller than 4 bytes. */
szCell[nCell] = 4;
}
}
nCell++;
}
}
}
/*
** Figure out the number of pages needed to hold all nCell cells.
** Store this number in "k". Also compute szNew[] which is the total
** size of all cells on the i-th page and cntNew[] which is the index
** in apCell[] of the cell that divides page i from page i+1.
** cntNew[k] should equal nCell.
**
** Values computed by this block:
**
** k: The total number of sibling pages
** szNew[i]: Spaced used on the i-th sibling page.
** cntNew[i]: Index in apCell[] and szCell[] for the first cell to
** the right of the i-th sibling page.
** usableSpace: Number of bytes of space available on each sibling.
**
*/
usableSpace = pBt->usableSize - 12 + leafCorrection;
for(subtotal=k=i=0; i<nCell; i++){
assert( i<nMaxCells );
subtotal += szCell[i] + 2;
if( subtotal > usableSpace ){
szNew[k] = subtotal - szCell[i];
cntNew[k] = i;
if( leafData ){ i--; }
subtotal = 0;
k++;
}
}
szNew[k] = subtotal;
cntNew[k] = nCell;
k++;
/*
** The packing computed by the previous block is biased toward the siblings
** on the left side. The left siblings are always nearly full, while the
** right-most sibling might be nearly empty. This block of code attempts
** to adjust the packing of siblings to get a better balance.
**
** This adjustment is more than an optimization. The packing above might
** be so out of balance as to be illegal. For example, the right-most
** sibling might be completely empty. This adjustment is not optional.
*/
for(i=k-1; i>0; i--){
int szRight = szNew[i]; /* Size of sibling on the right */
int szLeft = szNew[i-1]; /* Size of sibling on the left */
int r; /* Index of right-most cell in left sibling */
int d; /* Index of first cell to the left of right sibling */
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
assert( d<nMaxCells );
assert( r<nMaxCells );
while( szRight==0 || szRight+szCell[d]+2<=szLeft-(szCell[r]+2) ){
szRight += szCell[d] + 2;
szLeft -= szCell[r] + 2;
cntNew[i-1]--;
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
}
szNew[i] = szRight;
szNew[i-1] = szLeft;
}
/* Either we found one or more cells (cntnew[0])>0) or we are the
** a virtual root page. A virtual root page is when the real root
** page is page 1 and we are the only child of that page.
*/
assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) );
/*
** Allocate k new pages. Reuse old pages where possible.
*/
assert( pPage->pgno>1 );
pageFlags = pPage->aData[0];
for(i=0; i<k; i++){
MemPage *pNew;
if( i<nOld ){
pNew = apNew[i] = apOld[i];
pgnoNew[i] = pgnoOld[i];
apOld[i] = 0;
rc = sqlite3PagerWrite(pNew->pDbPage);
nNew++;
if( rc ) goto balance_cleanup;
}else{
assert( i>0 );
rc = allocateBtreePage(pBt, &pNew, &pgnoNew[i], pgnoNew[i-1], 0);
if( rc ) goto balance_cleanup;
apNew[i] = pNew;
nNew++;
}
}
/* Free any old pages that were not reused as new pages.
*/
while( i<nOld ){
rc = freePage(apOld[i]);
if( rc ) goto balance_cleanup;
releasePage(apOld[i]);
apOld[i] = 0;
i++;
}
/*
** Put the new pages in accending order. This helps to
** keep entries in the disk file in order so that a scan
** of the table is a linear scan through the file. That
** in turn helps the operating system to deliver pages
** from the disk more rapidly.
**
** An O(n^2) insertion sort algorithm is used, but since
** n is never more than NB (a small constant), that should
** not be a problem.
**
** When NB==3, this one optimization makes the database
** about 25% faster for large insertions and deletions.
*/
for(i=0; i<k-1; i++){
int minV = pgnoNew[i];
int minI = i;
for(j=i+1; j<k; j++){
if( pgnoNew[j]<(unsigned)minV ){
minI = j;
minV = pgnoNew[j];
}
}
if( minI>i ){
int t;
MemPage *pT;
t = pgnoNew[i];
pT = apNew[i];
pgnoNew[i] = pgnoNew[minI];
apNew[i] = apNew[minI];
pgnoNew[minI] = t;
apNew[minI] = pT;
}
}
TRACE(("BALANCE: old: %d %d %d new: %d(%d) %d(%d) %d(%d) %d(%d) %d(%d)\n",
pgnoOld[0],
nOld>=2 ? pgnoOld[1] : 0,
nOld>=3 ? pgnoOld[2] : 0,
pgnoNew[0], szNew[0],
nNew>=2 ? pgnoNew[1] : 0, nNew>=2 ? szNew[1] : 0,
nNew>=3 ? pgnoNew[2] : 0, nNew>=3 ? szNew[2] : 0,
nNew>=4 ? pgnoNew[3] : 0, nNew>=4 ? szNew[3] : 0,
nNew>=5 ? pgnoNew[4] : 0, nNew>=5 ? szNew[4] : 0));
/*
** Evenly distribute the data in apCell[] across the new pages.
** Insert divider cells into pParent as necessary.
*/
j = 0;
for(i=0; i<nNew; i++){
/* Assemble the new sibling page. */
MemPage *pNew = apNew[i];
assert( j<nMaxCells );
assert( pNew->pgno==pgnoNew[i] );
zeroPage(pNew, pageFlags);
assemblePage(pNew, cntNew[i]-j, &apCell[j], &szCell[j]);
assert( pNew->nCell>0 || (nNew==1 && cntNew[0]==0) );
assert( pNew->nOverflow==0 );
/* If this is an auto-vacuum database, update the pointer map entries
** that point to the siblings that were rearranged. These can be: left
** children of cells, the right-child of the page, or overflow pages
** pointed to by cells.
*/
if( ISAUTOVACUUM ){
for(k=j; k<cntNew[i]; k++){
assert( k<nMaxCells );
if( aFrom[k]==0xFF || apCopy[aFrom[k]]->pgno!=pNew->pgno ){
rc = ptrmapPutOvfl(pNew, k-j);
if( rc==SQLITE_OK && leafCorrection==0 ){
rc = ptrmapPut(pBt, get4byte(apCell[k]), PTRMAP_BTREE, pNew->pgno);
}
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
}
}
j = cntNew[i];
/* If the sibling page assembled above was not the right-most sibling,
** insert a divider cell into the parent page.
*/
if( i<nNew-1 && j<nCell ){
u8 *pCell;
u8 *pTemp;
int sz;
assert( j<nMaxCells );
pCell = apCell[j];
sz = szCell[j] + leafCorrection;
pTemp = &aSpace2[iSpace2];
if( !pNew->leaf ){
memcpy(&pNew->aData[8], pCell, 4);
if( ISAUTOVACUUM
&& (aFrom[j]==0xFF || apCopy[aFrom[j]]->pgno!=pNew->pgno)
){
rc = ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
}else if( leafData ){
/* If the tree is a leaf-data tree, and the siblings are leaves,
** then there is no divider cell in apCell[]. Instead, the divider
** cell consists of the integer key for the right-most cell of
** the sibling-page assembled above only.
*/
CellInfo info;
j--;
sqlite3BtreeParseCellPtr(pNew, apCell[j], &info);
pCell = pTemp;
fillInCell(pParent, pCell, 0, info.nKey, 0, 0, 0, &sz);
pTemp = 0;
}else{
pCell -= 4;
/* Obscure case for non-leaf-data trees: If the cell at pCell was
** previously stored on a leaf node, and its reported size was 4
** bytes, then it may actually be smaller than this
** (see sqlite3BtreeParseCellPtr(), 4 bytes is the minimum size of
** any cell). But it is important to pass the correct size to
** insertCell(), so reparse the cell now.
**
** Note that this can never happen in an SQLite data file, as all
** cells are at least 4 bytes. It only happens in b-trees used
** to evaluate "IN (SELECT ...)" and similar clauses.
*/
if( szCell[j]==4 ){
assert(leafCorrection==4);
sz = cellSizePtr(pParent, pCell);
}
}
iSpace2 += sz;
assert( sz<=pBt->pageSize/4 );
assert( iSpace2<=pBt->pageSize );
rc = insertCell(pParent, nxDiv, pCell, sz, pTemp, 4);
if( rc!=SQLITE_OK ) goto balance_cleanup;
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
put4byte(findOverflowCell(pParent,nxDiv), pNew->pgno);
/* If this is an auto-vacuum database, and not a leaf-data tree,
** then update the pointer map with an entry for the overflow page
** that the cell just inserted points to (if any).
*/
if( ISAUTOVACUUM && !leafData ){
rc = ptrmapPutOvfl(pParent, nxDiv);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
j++;
nxDiv++;
}
/* Set the pointer-map entry for the new sibling page. */
if( ISAUTOVACUUM ){
rc = ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
}
assert( j==nCell );
assert( nOld>0 );
assert( nNew>0 );
if( (pageFlags & PTF_LEAF)==0 ){
u8 *zChild = &apCopy[nOld-1]->aData[8];
memcpy(&apNew[nNew-1]->aData[8], zChild, 4);
if( ISAUTOVACUUM ){
rc = ptrmapPut(pBt, get4byte(zChild), PTRMAP_BTREE, apNew[nNew-1]->pgno);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
}
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
if( nxDiv==pParent->nCell+pParent->nOverflow ){
/* Right-most sibling is the right-most child of pParent */
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew[nNew-1]);
}else{
/* Right-most sibling is the left child of the first entry in pParent
** past the right-most divider entry */
put4byte(findOverflowCell(pParent, nxDiv), pgnoNew[nNew-1]);
}
/*
** Balance the parent page. Note that the current page (pPage) might
** have been added to the freelist so it might no longer be initialized.
** But the parent page will always be initialized.
*/
assert( pParent->isInit );
sqlite3ScratchFree(apCell);
apCell = 0;
releasePage(pPage);
pCur->iPage--;
rc = balance(pCur, 0);
/*
** Cleanup before returning.
*/
balance_cleanup:
sqlite3PageFree(aSpace2);
sqlite3ScratchFree(apCell);
for(i=0; i<nOld; i++){
releasePage(apOld[i]);
}
for(i=0; i<nNew; i++){
releasePage(apNew[i]);
}
pPage->nOverflow = 0;
/* releasePage(pParent); */
TRACE(("BALANCE: finished with %d: old=%d new=%d cells=%d\n",
pPage->pgno, nOld, nNew, nCell));
return rc;
}
/*
** This routine is called for the root page of a btree when the root
** page contains no cells. This is an opportunity to make the tree
** shallower by one level.
*/
static int balance_shallower(BtCursor *pCur){
MemPage *pPage; /* Root page of B-Tree */
MemPage *pChild; /* The only child page of pPage */
Pgno pgnoChild; /* Page number for pChild */
int rc = SQLITE_OK; /* Return code from subprocedures */
BtShared *pBt; /* The main BTree structure */
int mxCellPerPage; /* Maximum number of cells per page */
u8 **apCell; /* All cells from pages being balanced */
u16 *szCell; /* Local size of all cells */
assert( pCur->iPage==0 );
pPage = pCur->apPage[0];
assert( pPage->nCell==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pBt = pPage->pBt;
mxCellPerPage = MX_CELL(pBt);
apCell = sqlite3Malloc( mxCellPerPage*(sizeof(u8*)+sizeof(u16)) );
if( apCell==0 ) return SQLITE_NOMEM;
szCell = (u16*)&apCell[mxCellPerPage];
if( pPage->leaf ){
/* The table is completely empty */
TRACE(("BALANCE: empty table %d\n", pPage->pgno));
}else{
/* The root page is empty but has one child. Transfer the
** information from that one child into the root page if it
** will fit. This reduces the depth of the tree by one.
**
** If the root page is page 1, it has less space available than
** its child (due to the 100 byte header that occurs at the beginning
** of the database fle), so it might not be able to hold all of the
** information currently contained in the child. If this is the
** case, then do not do the transfer. Leave page 1 empty except
** for the right-pointer to the child page. The child page becomes
** the virtual root of the tree.
*/
VVA_ONLY( pCur->pagesShuffled = 1 );
pgnoChild = get4byte(&pPage->aData[pPage->hdrOffset+8]);
assert( pgnoChild>0 );
assert( pgnoChild<=pagerPagecount(pPage->pBt) );
rc = sqlite3BtreeGetPage(pPage->pBt, pgnoChild, &pChild, 0);
if( rc ) goto end_shallow_balance;
if( pPage->pgno==1 ){
rc = sqlite3BtreeInitPage(pChild);
if( rc ) goto end_shallow_balance;
assert( pChild->nOverflow==0 );
if( pChild->nFree>=100 ){
/* The child information will fit on the root page, so do the
** copy */
int i;
zeroPage(pPage, pChild->aData[0]);
for(i=0; i<pChild->nCell; i++){
apCell[i] = findCell(pChild,i);
szCell[i] = cellSizePtr(pChild, apCell[i]);
}
assemblePage(pPage, pChild->nCell, apCell, szCell);
/* Copy the right-pointer of the child to the parent. */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
put4byte(&pPage->aData[pPage->hdrOffset+8],
get4byte(&pChild->aData[pChild->hdrOffset+8]));
rc = freePage(pChild);
TRACE(("BALANCE: child %d transfer to page 1\n", pChild->pgno));
}else{
/* The child has more information that will fit on the root.
** The tree is already balanced. Do nothing. */
TRACE(("BALANCE: child %d will not fit on page 1\n", pChild->pgno));
}
}else{
memcpy(pPage->aData, pChild->aData, pPage->pBt->usableSize);
pPage->isInit = 0;
rc = sqlite3BtreeInitPage(pPage);
assert( rc==SQLITE_OK );
freePage(pChild);
TRACE(("BALANCE: transfer child %d into root %d\n",
pChild->pgno, pPage->pgno));
}
assert( pPage->nOverflow==0 );
#ifndef SQLITE_OMIT_AUTOVACUUM
if( ISAUTOVACUUM && rc==SQLITE_OK ){
rc = setChildPtrmaps(pPage);
}
#endif
releasePage(pChild);
}
end_shallow_balance:
sqlite3_free(apCell);
return rc;
}
/*
** The root page is overfull
**
** When this happens, Create a new child page and copy the
** contents of the root into the child. Then make the root
** page an empty page with rightChild pointing to the new
** child. Finally, call balance_internal() on the new child
** to cause it to split.
*/
static int balance_deeper(BtCursor *pCur){
int rc; /* Return value from subprocedures */
MemPage *pPage; /* Pointer to the root page */
MemPage *pChild; /* Pointer to a new child page */
Pgno pgnoChild; /* Page number of the new child page */
BtShared *pBt; /* The BTree */
int usableSize; /* Total usable size of a page */
u8 *data; /* Content of the parent page */
u8 *cdata; /* Content of the child page */
int hdr; /* Offset to page header in parent */
int cbrk; /* Offset to content of first cell in parent */
assert( pCur->iPage==0 );
assert( pCur->apPage[0]->nOverflow>0 );
VVA_ONLY( pCur->pagesShuffled = 1 );
pPage = pCur->apPage[0];
pBt = pPage->pBt;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
rc = allocateBtreePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
if( rc ) return rc;
assert( sqlite3PagerIswriteable(pChild->pDbPage) );
usableSize = pBt->usableSize;
data = pPage->aData;
hdr = pPage->hdrOffset;
cbrk = get2byte(&data[hdr+5]);
cdata = pChild->aData;
memcpy(cdata, &data[hdr], pPage->cellOffset+2*pPage->nCell-hdr);
memcpy(&cdata[cbrk], &data[cbrk], usableSize-cbrk);
assert( pChild->isInit==0 );
rc = sqlite3BtreeInitPage(pChild);
if( rc==SQLITE_OK ){
int nCopy = pPage->nOverflow*sizeof(pPage->aOvfl[0]);
memcpy(pChild->aOvfl, pPage->aOvfl, nCopy);
pChild->nOverflow = pPage->nOverflow;
if( pChild->nOverflow ){
pChild->nFree = 0;
}
assert( pChild->nCell==pPage->nCell );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
zeroPage(pPage, pChild->aData[0] & ~PTF_LEAF);
put4byte(&pPage->aData[pPage->hdrOffset+8], pgnoChild);
TRACE(("BALANCE: copy root %d into %d\n", pPage->pgno, pChild->pgno));
if( ISAUTOVACUUM ){
rc = ptrmapPut(pBt, pChild->pgno, PTRMAP_BTREE, pPage->pgno);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( rc==SQLITE_OK ){
rc = setChildPtrmaps(pChild);
}
#endif
}
}
if( rc==SQLITE_OK ){
pCur->iPage++;
pCur->apPage[1] = pChild;
pCur->aiIdx[0] = 0;
rc = balance_nonroot(pCur);
}else{
releasePage(pChild);
}
return rc;
}
/*
** The page that pCur currently points to has just been modified in
** some way. This function figures out if this modification means the
** tree needs to be balanced, and if so calls the appropriate balancing
** routine.
**
** Parameter isInsert is true if a new cell was just inserted into the
** page, or false otherwise.
*/
static int balance(BtCursor *pCur, int isInsert){
int rc = SQLITE_OK;
MemPage *pPage = pCur->apPage[pCur->iPage];
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
if( pCur->iPage==0 ){
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc==SQLITE_OK && pPage->nOverflow>0 ){
rc = balance_deeper(pCur);
assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
}
if( rc==SQLITE_OK && pPage->nCell==0 ){
rc = balance_shallower(pCur);
assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
}
}else{
if( pPage->nOverflow>0 ||
(!isInsert && pPage->nFree>pPage->pBt->usableSize*2/3) ){
rc = balance_nonroot(pCur);
assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
}
}
return rc;
}
/*
** This routine checks all cursors that point to table pgnoRoot.
** If any of those cursors were opened with wrFlag==0 in a different
** database connection (a database connection that shares the pager
** cache with the current connection) and that other connection
** is not in the ReadUncommmitted state, then this routine returns
** SQLITE_LOCKED.
**
** As well as cursors with wrFlag==0, cursors with wrFlag==1 and
** isIncrblobHandle==1 are also considered 'read' cursors. Incremental
** blob cursors are used for both reading and writing.
**
** When pgnoRoot is the root page of an intkey table, this function is also
** responsible for invalidating incremental blob cursors when the table row
** on which they are opened is deleted or modified. Cursors are invalidated
** according to the following rules:
**
** 1) When BtreeClearTable() is called to completely delete the contents
** of a B-Tree table, pExclude is set to zero and parameter iRow is
** set to non-zero. In this case all incremental blob cursors open
** on the table rooted at pgnoRoot are invalidated.
**
** 2) When BtreeInsert(), BtreeDelete() or BtreePutData() is called to
** modify a table row via an SQL statement, pExclude is set to the
** write cursor used to do the modification and parameter iRow is set
** to the integer row id of the B-Tree entry being modified. Unless
** pExclude is itself an incremental blob cursor, then all incremental
** blob cursors open on row iRow of the B-Tree are invalidated.
**
** 3) If both pExclude and iRow are set to zero, no incremental blob
** cursors are invalidated.
*/
static int checkReadLocks(
Btree *pBtree,
Pgno pgnoRoot,
BtCursor *pExclude,
i64 iRow
){
BtCursor *p;
BtShared *pBt = pBtree->pBt;
sqlite3 *db = pBtree->db;
assert( sqlite3BtreeHoldsMutex(pBtree) );
for(p=pBt->pCursor; p; p=p->pNext){
if( p==pExclude ) continue;
if( p->pgnoRoot!=pgnoRoot ) continue;
#ifndef SQLITE_OMIT_INCRBLOB
if( p->isIncrblobHandle && (
(!pExclude && iRow)
|| (pExclude && !pExclude->isIncrblobHandle && p->info.nKey==iRow)
)){
p->eState = CURSOR_INVALID;
}
#endif
if( p->eState!=CURSOR_VALID ) continue;
if( p->wrFlag==0
#ifndef SQLITE_OMIT_INCRBLOB
|| p->isIncrblobHandle
#endif
){
sqlite3 *dbOther = p->pBtree->db;
if( dbOther==0 ||
(dbOther!=db && (dbOther->flags & SQLITE_ReadUncommitted)==0) ){
return SQLITE_LOCKED;
}
}
}
return SQLITE_OK;
}
/*
** Insert a new record into the BTree. The key is given by (pKey,nKey)
** and the data is given by (pData,nData). The cursor is used only to
** define what table the record should be inserted into. The cursor
** is left pointing at a random location.
**
** For an INTKEY table, only the nKey value of the key is used. pKey is
** ignored. For a ZERODATA table, the pData and nData are both ignored.
*/
int sqlite3BtreeInsert(
BtCursor *pCur, /* Insert data into the table of this cursor */
const void *pKey, i64 nKey, /* The key of the new record */
const void *pData, int nData, /* The data of the new record */
int nZero, /* Number of extra 0 bytes to append to data */
int appendBias /* True if this is likely an append */
){
int rc;
int loc;
int szNew;
int idx;
MemPage *pPage;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
unsigned char *oldCell;
unsigned char *newCell = 0;
assert( cursorHoldsMutex(pCur) );
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction before doing an insert */
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
return rc;
}
assert( !pBt->readOnly );
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Cursor not open for writing */
}
if( checkReadLocks(pCur->pBtree, pCur->pgnoRoot, pCur, nKey) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
/* Save the positions of any other cursors open on this table */
sqlite3BtreeClearCursor(pCur);
if(
SQLITE_OK!=(rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur)) ||
SQLITE_OK!=(rc = sqlite3BtreeMoveto(pCur, pKey, nKey, appendBias, &loc))
){
return rc;
}
pPage = pCur->apPage[pCur->iPage];
assert( pPage->intKey || nKey>=0 );
assert( pPage->leaf || !pPage->intKey );
TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
pCur->pgnoRoot, nKey, nData, pPage->pgno,
loc==0 ? "overwrite" : "new entry"));
assert( pPage->isInit );
allocateTempSpace(pBt);
newCell = pBt->pTmpSpace;
if( newCell==0 ) return SQLITE_NOMEM;
rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, nZero, &szNew);
if( rc ) goto end_insert;
assert( szNew==cellSizePtr(pPage, newCell) );
assert( szNew<=MX_CELL_SIZE(pBt) );
idx = pCur->aiIdx[pCur->iPage];
if( loc==0 && CURSOR_VALID==pCur->eState ){
u16 szOld;
assert( idx<pPage->nCell );
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ){
goto end_insert;
}
oldCell = findCell(pPage, idx);
if( !pPage->leaf ){
memcpy(newCell, oldCell, 4);
}
szOld = cellSizePtr(pPage, oldCell);
rc = clearCell(pPage, oldCell);
if( rc ) goto end_insert;
rc = dropCell(pPage, idx, szOld);
if( rc!=SQLITE_OK ) {
goto end_insert;
}
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->leaf );
idx = ++pCur->aiIdx[pCur->iPage];
pCur->info.nSize = 0;
pCur->validNKey = 0;
}else{
assert( pPage->leaf );
}
rc = insertCell(pPage, idx, newCell, szNew, 0, 0);
if( rc==SQLITE_OK ){
rc = balance(pCur, 1);
}
/* Must make sure nOverflow is reset to zero even if the balance()
** fails. Internal data structure corruption will result otherwise. */
assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
pPage->nOverflow = 0;
if( rc==SQLITE_OK ){
moveToRoot(pCur);
}
end_insert:
return rc;
}
/*
** Delete the entry that the cursor is pointing to. The cursor
** is left pointing at a arbitrary location.
*/
int sqlite3BtreeDelete(BtCursor *pCur){
MemPage *pPage = pCur->apPage[pCur->iPage];
int idx;
unsigned char *pCell;
int rc;
Pgno pgnoChild = 0;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
assert( cursorHoldsMutex(pCur) );
assert( pPage->isInit );
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction before doing a delete */
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
return rc;
}
assert( !pBt->readOnly );
if( pCur->eState==CURSOR_FAULT ){
return pCur->skip;
}
if( pCur->aiIdx[pCur->iPage]>=pPage->nCell ){
return SQLITE_ERROR; /* The cursor is not pointing to anything */
}
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Did not open this cursor for writing */
}
if( checkReadLocks(pCur->pBtree, pCur->pgnoRoot, pCur, pCur->info.nKey) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
/* Restore the current cursor position (a no-op if the cursor is not in
** CURSOR_REQUIRESEEK state) and save the positions of any other cursors
** open on the same table. Then call sqlite3PagerWrite() on the page
** that the entry will be deleted from.
*/
if(
(rc = restoreCursorPosition(pCur))!=0 ||
(rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur))!=0 ||
(rc = sqlite3PagerWrite(pPage->pDbPage))!=0
){
return rc;
}
/* Locate the cell within its page and leave pCell pointing to the
** data. The clearCell() call frees any overflow pages associated with the
** cell. The cell itself is still intact.
*/
idx = pCur->aiIdx[pCur->iPage];
pCell = findCell(pPage, idx);
if( !pPage->leaf ){
pgnoChild = get4byte(pCell);
}
rc = clearCell(pPage, pCell);
if( rc ){
return rc;
}
if( !pPage->leaf ){
/*
** The entry we are about to delete is not a leaf so if we do not
** do something we will leave a hole on an internal page.
** We have to fill the hole by moving in a cell from a leaf. The
** next Cell after the one to be deleted is guaranteed to exist and
** to be a leaf so we can use it.
*/
BtCursor leafCur;
MemPage *pLeafPage;
unsigned char *pNext;
int notUsed;
unsigned char *tempCell = 0;
assert( !pPage->intKey );
sqlite3BtreeGetTempCursor(pCur, &leafCur);
rc = sqlite3BtreeNext(&leafCur, &notUsed);
if( rc==SQLITE_OK ){
assert( leafCur.aiIdx[leafCur.iPage]==0 );
pLeafPage = leafCur.apPage[leafCur.iPage];
rc = sqlite3PagerWrite(pLeafPage->pDbPage);
}
if( rc==SQLITE_OK ){
int leafCursorInvalid = 0;
u16 szNext;
TRACE(("DELETE: table=%d delete internal from %d replace from leaf %d\n",
pCur->pgnoRoot, pPage->pgno, pLeafPage->pgno));
dropCell(pPage, idx, cellSizePtr(pPage, pCell));
pNext = findCell(pLeafPage, 0);
szNext = cellSizePtr(pLeafPage, pNext);
assert( MX_CELL_SIZE(pBt)>=szNext+4 );
allocateTempSpace(pBt);
tempCell = pBt->pTmpSpace;
if( tempCell==0 ){
rc = SQLITE_NOMEM;
}
if( rc==SQLITE_OK ){
rc = insertCell(pPage, idx, pNext-4, szNext+4, tempCell, 0);
}
/* The "if" statement in the next code block is critical. The
** slightest error in that statement would allow SQLite to operate
** correctly most of the time but produce very rare failures. To
** guard against this, the following macros help to verify that
** the "if" statement is well tested.
*/
testcase( pPage->nOverflow==0 && pPage->nFree<pBt->usableSize*2/3
&& pLeafPage->nFree+2+szNext > pBt->usableSize*2/3 );
testcase( pPage->nOverflow==0 && pPage->nFree==pBt->usableSize*2/3
&& pLeafPage->nFree+2+szNext > pBt->usableSize*2/3 );
testcase( pPage->nOverflow==0 && pPage->nFree==pBt->usableSize*2/3+1
&& pLeafPage->nFree+2+szNext > pBt->usableSize*2/3 );
testcase( pPage->nOverflow>0 && pPage->nFree<=pBt->usableSize*2/3
&& pLeafPage->nFree+2+szNext > pBt->usableSize*2/3 );
testcase( (pPage->nOverflow>0 || (pPage->nFree > pBt->usableSize*2/3))
&& pLeafPage->nFree+2+szNext == pBt->usableSize*2/3 );
if( (pPage->nOverflow>0 || (pPage->nFree > pBt->usableSize*2/3)) &&
(pLeafPage->nFree+2+szNext > pBt->usableSize*2/3)
){
/* This branch is taken if the internal node is now either overflowing
** or underfull and the leaf node will be underfull after the just cell
** copied to the internal node is deleted from it. This is a special
** case because the call to balance() to correct the internal node
** may change the tree structure and invalidate the contents of
** the leafCur.apPage[] and leafCur.aiIdx[] arrays, which will be
** used by the balance() required to correct the underfull leaf
** node.
**
** The formula used in the expression above are based on facets of
** the SQLite file-format that do not change over time.
*/
testcase( pPage->nFree==pBt->usableSize*2/3+1 );
testcase( pLeafPage->nFree+2+szNext==pBt->usableSize*2/3+1 );
leafCursorInvalid = 1;
}
if( rc==SQLITE_OK ){
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
put4byte(findOverflowCell(pPage, idx), pgnoChild);
VVA_ONLY( pCur->pagesShuffled = 0 );
rc = balance(pCur, 0);
}
if( rc==SQLITE_OK && leafCursorInvalid ){
/* The leaf-node is now underfull and so the tree needs to be
** rebalanced. However, the balance() operation on the internal
** node above may have modified the structure of the B-Tree and
** so the current contents of leafCur.apPage[] and leafCur.aiIdx[]
** may not be trusted.
**
** It is not possible to copy the ancestry from pCur, as the same
** balance() call has invalidated the pCur->apPage[] and aiIdx[]
** arrays.
**
** The call to saveCursorPosition() below internally saves the
** key that leafCur is currently pointing to. Currently, there
** are two copies of that key in the tree - one here on the leaf
** page and one on some internal node in the tree. The copy on
** the leaf node is always the next key in tree-order after the
** copy on the internal node. So, the call to sqlite3BtreeNext()
** calls restoreCursorPosition() to point the cursor to the copy
** stored on the internal node, then advances to the next entry,
** which happens to be the copy of the key on the internal node.
** Net effect: leafCur is pointing back to the duplicate cell
** that needs to be removed, and the leafCur.apPage[] and
** leafCur.aiIdx[] arrays are correct.
*/
VVA_ONLY( Pgno leafPgno = pLeafPage->pgno );
rc = saveCursorPosition(&leafCur);
if( rc==SQLITE_OK ){
rc = sqlite3BtreeNext(&leafCur, &notUsed);
}
pLeafPage = leafCur.apPage[leafCur.iPage];
assert( pLeafPage->pgno==leafPgno );
assert( leafCur.aiIdx[leafCur.iPage]==0 );
}
if( SQLITE_OK==rc
&& SQLITE_OK==(rc = sqlite3PagerWrite(pLeafPage->pDbPage))
){
dropCell(pLeafPage, 0, szNext);
VVA_ONLY( leafCur.pagesShuffled = 0 );
rc = balance(&leafCur, 0);
assert( leafCursorInvalid || !leafCur.pagesShuffled
|| !pCur->pagesShuffled );
}
}
sqlite3BtreeReleaseTempCursor(&leafCur);
}else{
TRACE(("DELETE: table=%d delete from leaf %d\n",
pCur->pgnoRoot, pPage->pgno));
rc = dropCell(pPage, idx, cellSizePtr(pPage, pCell));
if( rc==SQLITE_OK ){
rc = balance(pCur, 0);
}
}
if( rc==SQLITE_OK ){
moveToRoot(pCur);
}
return rc;
}
/*
** Create a new BTree table. Write into *piTable the page
** number for the root page of the new table.
**
** The type of type is determined by the flags parameter. Only the
** following values of flags are currently in use. Other values for
** flags might not work:
**
** BTREE_INTKEY|BTREE_LEAFDATA Used for SQL tables with rowid keys
** BTREE_ZERODATA Used for SQL indices
*/
static int btreeCreateTable(Btree *p, int *piTable, int flags){
BtShared *pBt = p->pBt;
MemPage *pRoot;
Pgno pgnoRoot;
int rc;
assert( sqlite3BtreeHoldsMutex(p) );
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction first */
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
return rc;
}
assert( !pBt->readOnly );
#ifdef SQLITE_OMIT_AUTOVACUUM
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ){
return rc;
}
#else
if( pBt->autoVacuum ){
Pgno pgnoMove; /* Move a page here to make room for the root-page */
MemPage *pPageMove; /* The page to move to. */
/* Creating a new table may probably require moving an existing database
** to make room for the new tables root page. In case this page turns
** out to be an overflow page, delete all overflow page-map caches
** held by open cursors.
*/
invalidateAllOverflowCache(pBt);
/* Read the value of meta[3] from the database to determine where the
** root page of the new table should go. meta[3] is the largest root-page
** created so far, so the new root-page is (meta[3]+1).
*/
rc = sqlite3BtreeGetMeta(p, 4, &pgnoRoot);
if( rc!=SQLITE_OK ){
return rc;
}
pgnoRoot++;
/* The new root-page may not be allocated on a pointer-map page, or the
** PENDING_BYTE page.
*/
while( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
pgnoRoot++;
}
assert( pgnoRoot>=3 );
/* Allocate a page. The page that currently resides at pgnoRoot will
** be moved to the allocated page (unless the allocated page happens
** to reside at pgnoRoot).
*/
rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, 1);
if( rc!=SQLITE_OK ){
return rc;
}
if( pgnoMove!=pgnoRoot ){
/* pgnoRoot is the page that will be used for the root-page of
** the new table (assuming an error did not occur). But we were
** allocated pgnoMove. If required (i.e. if it was not allocated
** by extending the file), the current page at position pgnoMove
** is already journaled.
*/
u8 eType;
Pgno iPtrPage;
releasePage(pPageMove);
/* Move the page currently at pgnoRoot to pgnoMove. */
rc = sqlite3BtreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
if( rc!=SQLITE_OK || eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
releasePage(pRoot);
return rc;
}
assert( eType!=PTRMAP_ROOTPAGE );
assert( eType!=PTRMAP_FREEPAGE );
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove, 0);
releasePage(pRoot);
/* Obtain the page at pgnoRoot */
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3BtreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
}else{
pRoot = pPageMove;
}
/* Update the pointer-map and meta-data with the new root-page number. */
rc = ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0);
if( rc ){
releasePage(pRoot);
return rc;
}
rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
if( rc ){
releasePage(pRoot);
return rc;
}
}else{
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ) return rc;
}
#endif
assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
zeroPage(pRoot, flags | PTF_LEAF);
sqlite3PagerUnref(pRoot->pDbPage);
*piTable = (int)pgnoRoot;
return SQLITE_OK;
}
int sqlite3BtreeCreateTable(Btree *p, int *piTable, int flags){
int rc;
sqlite3BtreeEnter(p);
p->pBt->db = p->db;
rc = btreeCreateTable(p, piTable, flags);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Erase the given database page and all its children. Return
** the page to the freelist.
*/
static int clearDatabasePage(
BtShared *pBt, /* The BTree that contains the table */
Pgno pgno, /* Page number to clear */
int freePageFlag, /* Deallocate page if true */
int *pnChange
){
MemPage *pPage = 0;
int rc;
unsigned char *pCell;
int i;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno>pagerPagecount(pBt) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getAndInitPage(pBt, pgno, &pPage);
if( rc ) goto cleardatabasepage_out;
for(i=0; i<pPage->nCell; i++){
pCell = findCell(pPage, i);
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(pCell), 1, pnChange);
if( rc ) goto cleardatabasepage_out;
}
rc = clearCell(pPage, pCell);
if( rc ) goto cleardatabasepage_out;
}
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(&pPage->aData[8]), 1, pnChange);
if( rc ) goto cleardatabasepage_out;
}else if( pnChange ){
assert( pPage->intKey );
*pnChange += pPage->nCell;
}
if( freePageFlag ){
rc = freePage(pPage);
}else if( (rc = sqlite3PagerWrite(pPage->pDbPage))==0 ){
zeroPage(pPage, pPage->aData[0] | PTF_LEAF);
}
cleardatabasepage_out:
releasePage(pPage);
return rc;
}
/*
** Delete all information from a single table in the database. iTable is
** the page number of the root of the table. After this routine returns,
** the root page is empty, but still exists.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** read cursors on the table. Open write cursors are moved to the
** root of the table.
**
** If pnChange is not NULL, then table iTable must be an intkey table. The
** integer value pointed to by pnChange is incremented by the number of
** entries in the table.
*/
int sqlite3BtreeClearTable(Btree *p, int iTable, int *pnChange){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
pBt->db = p->db;
if( p->inTrans!=TRANS_WRITE ){
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}else if( (rc = checkReadLocks(p, iTable, 0, 1))!=SQLITE_OK ){
/* nothing to do */
}else if( SQLITE_OK!=(rc = saveAllCursors(pBt, iTable, 0)) ){
/* nothing to do */
}else{
rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Erase all information in a table and add the root of the table to
** the freelist. Except, the root of the principle table (the one on
** page 1) is never added to the freelist.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** cursors on the table.
**
** If AUTOVACUUM is enabled and the page at iTable is not the last
** root page in the database file, then the last root page
** in the database file is moved into the slot formerly occupied by
** iTable and that last slot formerly occupied by the last root page
** is added to the freelist instead of iTable. In this say, all
** root pages are kept at the beginning of the database file, which
** is necessary for AUTOVACUUM to work right. *piMoved is set to the
** page number that used to be the last root page in the file before
** the move. If no page gets moved, *piMoved is set to 0.
** The last root page is recorded in meta[3] and the value of
** meta[3] is updated by this procedure.
*/
static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
int rc;
MemPage *pPage = 0;
BtShared *pBt = p->pBt;
assert( sqlite3BtreeHoldsMutex(p) );
if( p->inTrans!=TRANS_WRITE ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
/* It is illegal to drop a table if any cursors are open on the
** database. This is because in auto-vacuum mode the backend may
** need to move another root-page to fill a gap left by the deleted
** root page. If an open cursor was using this page a problem would
** occur.
*/
if( pBt->pCursor ){
return SQLITE_LOCKED;
}
rc = sqlite3BtreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
if( rc ) return rc;
rc = sqlite3BtreeClearTable(p, iTable, 0);
if( rc ){
releasePage(pPage);
return rc;
}
*piMoved = 0;
if( iTable>1 ){
#ifdef SQLITE_OMIT_AUTOVACUUM
rc = freePage(pPage);
releasePage(pPage);
#else
if( pBt->autoVacuum ){
Pgno maxRootPgno;
rc = sqlite3BtreeGetMeta(p, 4, &maxRootPgno);
if( rc!=SQLITE_OK ){
releasePage(pPage);
return rc;
}
if( iTable==maxRootPgno ){
/* If the table being dropped is the table with the largest root-page
** number in the database, put the root page on the free list.
*/
rc = freePage(pPage);
releasePage(pPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
/* The table being dropped does not have the largest root-page
** number in the database. So move the page that does into the
** gap left by the deleted root-page.
*/
MemPage *pMove;
releasePage(pPage);
rc = sqlite3BtreeGetPage(pBt, maxRootPgno, &pMove, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable, 0);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3BtreeGetPage(pBt, maxRootPgno, &pMove, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = freePage(pMove);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
*piMoved = maxRootPgno;
}
/* Set the new 'max-root-page' value in the database header. This
** is the old value less one, less one more if that happens to
** be a root-page number, less one again if that is the
** PENDING_BYTE_PAGE.
*/
maxRootPgno--;
if( maxRootPgno==PENDING_BYTE_PAGE(pBt) ){
maxRootPgno--;
}
if( maxRootPgno==PTRMAP_PAGENO(pBt, maxRootPgno) ){
maxRootPgno--;
}
assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );
rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
}else{
rc = freePage(pPage);
releasePage(pPage);
}
#endif
}else{
/* If sqlite3BtreeDropTable was called on page 1. */
zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
releasePage(pPage);
}
return rc;
}
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
int rc;
sqlite3BtreeEnter(p);
p->pBt->db = p->db;
rc = btreeDropTable(p, iTable, piMoved);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Read the meta-information out of a database file. Meta[0]
** is the number of free pages currently in the database. Meta[1]
** through meta[15] are available for use by higher layers. Meta[0]
** is read-only, the others are read/write.
**
** The schema layer numbers meta values differently. At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible. So Cookie[0] is the same as Meta[1].
*/
int sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
DbPage *pDbPage;
int rc;
unsigned char *pP1;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
pBt->db = p->db;
/* Reading a meta-data value requires a read-lock on page 1 (and hence
** the sqlite_master table. We grab this lock regardless of whether or
** not the SQLITE_ReadUncommitted flag is set (the table rooted at page
** 1 is treated as a special case by queryTableLock() and lockTable()).
*/
rc = queryTableLock(p, 1, READ_LOCK);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
assert( idx>=0 && idx<=15 );
if( pBt->pPage1 ){
/* The b-tree is already holding a reference to page 1 of the database
** file. In this case the required meta-data value can be read directly
** from the page data of this reference. This is slightly faster than
** requesting a new reference from the pager layer.
*/
pP1 = (unsigned char *)pBt->pPage1->aData;
}else{
/* The b-tree does not have a reference to page 1 of the database file.
** Obtain one from the pager layer.
*/
rc = sqlite3PagerGet(pBt->pPager, 1, &pDbPage);
if( rc ){
sqlite3BtreeLeave(p);
return rc;
}
pP1 = (unsigned char *)sqlite3PagerGetData(pDbPage);
}
*pMeta = get4byte(&pP1[36 + idx*4]);
/* If the b-tree is not holding a reference to page 1, then one was
** requested from the pager layer in the above block. Release it now.
*/
if( !pBt->pPage1 ){
sqlite3PagerUnref(pDbPage);
}
/* If autovacuumed is disabled in this build but we are trying to
** access an autovacuumed database, then make the database readonly.
*/
#ifdef SQLITE_OMIT_AUTOVACUUM
if( idx==4 && *pMeta>0 ) pBt->readOnly = 1;
#endif
/* Grab the read-lock on page 1. */
rc = lockTable(p, 1, READ_LOCK);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Write meta-information back into the database. Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
BtShared *pBt = p->pBt;
unsigned char *pP1;
int rc;
assert( idx>=1 && idx<=15 );
sqlite3BtreeEnter(p);
pBt->db = p->db;
if( p->inTrans!=TRANS_WRITE ){
rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}else{
assert( pBt->pPage1!=0 );
pP1 = pBt->pPage1->aData;
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pP1[36 + idx*4], iMeta);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( idx==7 ){
assert( pBt->autoVacuum || iMeta==0 );
assert( iMeta==0 || iMeta==1 );
pBt->incrVacuum = iMeta;
}
#endif
}
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Return the flag byte at the beginning of the page that the cursor
** is currently pointing to.
*/
int sqlite3BtreeFlags(BtCursor *pCur){
/* TODO: What about CURSOR_REQUIRESEEK state? Probably need to call
** restoreCursorPosition() here.
*/
MemPage *pPage;
restoreCursorPosition(pCur);
pPage = pCur->apPage[pCur->iPage];
assert( cursorHoldsMutex(pCur) );
assert( pPage->pBt==pCur->pBt );
return pPage ? pPage->aData[pPage->hdrOffset] : 0;
}
/*
** Return the pager associated with a BTree. This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *p){
return p->pBt->pPager;
}
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(
IntegrityCk *pCheck,
char *zMsg1,
const char *zFormat,
...
){
va_list ap;
if( !pCheck->mxErr ) return;
pCheck->mxErr--;
pCheck->nErr++;
va_start(ap, zFormat);
if( pCheck->errMsg.nChar ){
sqlite3StrAccumAppend(&pCheck->errMsg, "\n", 1);
}
if( zMsg1 ){
sqlite3StrAccumAppend(&pCheck->errMsg, zMsg1, -1);
}
sqlite3VXPrintf(&pCheck->errMsg, 1, zFormat, ap);
va_end(ap);
if( pCheck->errMsg.mallocFailed ){
pCheck->mallocFailed = 1;
}
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Add 1 to the reference count for page iPage. If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 ore more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, Pgno iPage, char *zContext){
if( iPage==0 ) return 1;
if( iPage>pCheck->nPage ){
checkAppendMsg(pCheck, zContext, "invalid page number %d", iPage);
return 1;
}
if( pCheck->anRef[iPage]==1 ){
checkAppendMsg(pCheck, zContext, "2nd reference to page %d", iPage);
return 1;
}
return (pCheck->anRef[iPage]++)>1;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Check that the entry in the pointer-map for page iChild maps to
** page iParent, pointer type ptrType. If not, append an error message
** to pCheck.
*/
static void checkPtrmap(
IntegrityCk *pCheck, /* Integrity check context */
Pgno iChild, /* Child page number */
u8 eType, /* Expected pointer map type */
Pgno iParent, /* Expected pointer map parent page number */
char *zContext /* Context description (used for error msg) */
){
int rc;
u8 ePtrmapType;
Pgno iPtrmapParent;
rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM ) pCheck->mallocFailed = 1;
checkAppendMsg(pCheck, zContext, "Failed to read ptrmap key=%d", iChild);
return;
}
if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
checkAppendMsg(pCheck, zContext,
"Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)",
iChild, eType, iParent, ePtrmapType, iPtrmapParent);
}
}
#endif
/*
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
IntegrityCk *pCheck, /* Integrity checking context */
int isFreeList, /* True for a freelist. False for overflow page list */
int iPage, /* Page number for first page in the list */
int N, /* Expected number of pages in the list */
char *zContext /* Context for error messages */
){
int i;
int expected = N;
int iFirst = iPage;
while( N-- > 0 && pCheck->mxErr ){
DbPage *pOvflPage;
unsigned char *pOvflData;
if( iPage<1 ){
checkAppendMsg(pCheck, zContext,
"%d of %d pages missing from overflow list starting at %d",
N+1, expected, iFirst);
break;
}
if( checkRef(pCheck, iPage, zContext) ) break;
if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage) ){
checkAppendMsg(pCheck, zContext, "failed to get page %d", iPage);
break;
}
pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
if( isFreeList ){
int n = get4byte(&pOvflData[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0, zContext);
}
#endif
if( n>pCheck->pBt->usableSize/4-2 ){
checkAppendMsg(pCheck, zContext,
"freelist leaf count too big on page %d", iPage);
N--;
}else{
for(i=0; i<n; i++){
Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0, zContext);
}
#endif
checkRef(pCheck, iFreePage, zContext);
}
N -= n;
}
}
#ifndef SQLITE_OMIT_AUTOVACUUM
else{
/* If this database supports auto-vacuum and iPage is not the last
** page in this overflow list, check that the pointer-map entry for
** the following page matches iPage.
*/
if( pCheck->pBt->autoVacuum && N>0 ){
i = get4byte(pOvflData);
checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage, zContext);
}
}
#endif
iPage = get4byte(pOvflData);
sqlite3PagerUnref(pOvflPage);
}
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Do various sanity checks on a single page of a tree. Return
** the tree depth. Root pages return 0. Parents of root pages
** return 1, and so forth.
**
** These checks are done:
**
** 1. Make sure that cells and freeblocks do not overlap
** but combine to completely cover the page.
** NO 2. Make sure cell keys are in order.
** NO 3. Make sure no key is less than or equal to zLowerBound.
** NO 4. Make sure no key is greater than or equal to zUpperBound.
** 5. Check the integrity of overflow pages.
** 6. Recursively call checkTreePage on all children.
** 7. Verify that the depth of all children is the same.
** 8. Make sure this page is at least 33% full or else it is
** the root of the tree.
*/
static int checkTreePage(
IntegrityCk *pCheck, /* Context for the sanity check */
int iPage, /* Page number of the page to check */
char *zParentContext /* Parent context */
){
MemPage *pPage;
int i, rc, depth, d2, pgno, cnt;
int hdr, cellStart;
int nCell;
u8 *data;
BtShared *pBt;
int usableSize;
char zContext[100];
char *hit = 0;
sqlite3_snprintf(sizeof(zContext), zContext, "Page %d: ", iPage);
/* Check that the page exists
*/
pBt = pCheck->pBt;
usableSize = pBt->usableSize;
if( iPage==0 ) return 0;
if( checkRef(pCheck, iPage, zParentContext) ) return 0;
if( (rc = sqlite3BtreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
if( rc==SQLITE_NOMEM ) pCheck->mallocFailed = 1;
checkAppendMsg(pCheck, zContext,
"unable to get the page. error code=%d", rc);
return 0;
}
if( (rc = sqlite3BtreeInitPage(pPage))!=0 ){
if( rc==SQLITE_NOMEM ) pCheck->mallocFailed = 1;
checkAppendMsg(pCheck, zContext,
"sqlite3BtreeInitPage() returns error code %d", rc);
releasePage(pPage);
return 0;
}
/* Check out all the cells.
*/
depth = 0;
for(i=0; i<pPage->nCell && pCheck->mxErr; i++){
u8 *pCell;
u32 sz;
CellInfo info;
/* Check payload overflow pages
*/
sqlite3_snprintf(sizeof(zContext), zContext,
"On tree page %d cell %d: ", iPage, i);
pCell = findCell(pPage,i);
sqlite3BtreeParseCellPtr(pPage, pCell, &info);
sz = info.nData;
if( !pPage->intKey ) sz += info.nKey;
assert( sz==info.nPayload );
if( sz>info.nLocal ){
int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage, zContext);
}
#endif
checkList(pCheck, 0, pgnoOvfl, nPage, zContext);
}
/* Check sanity of left child page.
*/
if( !pPage->leaf ){
pgno = get4byte(pCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
}
#endif
d2 = checkTreePage(pCheck, pgno, zContext);
if( i>0 && d2!=depth ){
checkAppendMsg(pCheck, zContext, "Child page depth differs");
}
depth = d2;
}
}
if( !pPage->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
sqlite3_snprintf(sizeof(zContext), zContext,
"On page %d at right child: ", iPage);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, 0);
}
#endif
checkTreePage(pCheck, pgno, zContext);
}
/* Check for complete coverage of the page
*/
data = pPage->aData;
hdr = pPage->hdrOffset;
hit = sqlite3PageMalloc( pBt->pageSize );
if( hit==0 ){
pCheck->mallocFailed = 1;
}else{
u16 contentOffset = get2byte(&data[hdr+5]);
if (contentOffset > usableSize) {
checkAppendMsg(pCheck, 0,
"Corruption detected in header on page %d",iPage,0);
goto check_page_abort;
}
memset(hit+contentOffset, 0, usableSize-contentOffset);
memset(hit, 1, contentOffset);
nCell = get2byte(&data[hdr+3]);
cellStart = hdr + 12 - 4*pPage->leaf;
for(i=0; i<nCell; i++){
int pc = get2byte(&data[cellStart+i*2]);
u16 size = 1024;
int j;
if( pc<=usableSize ){
size = cellSizePtr(pPage, &data[pc]);
}
if( (pc+size-1)>=usableSize || pc<0 ){
checkAppendMsg(pCheck, 0,
"Corruption detected in cell %d on page %d",i,iPage,0);
}else{
for(j=pc+size-1; j>=pc; j--) hit[j]++;
}
}
for(cnt=0, i=get2byte(&data[hdr+1]); i>0 && i<usableSize && cnt<10000;
cnt++){
int size = get2byte(&data[i+2]);
int j;
if( (i+size-1)>=usableSize || i<0 ){
checkAppendMsg(pCheck, 0,
"Corruption detected in cell %d on page %d",i,iPage,0);
}else{
for(j=i+size-1; j>=i; j--) hit[j]++;
}
i = get2byte(&data[i]);
}
for(i=cnt=0; i<usableSize; i++){
if( hit[i]==0 ){
cnt++;
}else if( hit[i]>1 ){
checkAppendMsg(pCheck, 0,
"Multiple uses for byte %d of page %d", i, iPage);
break;
}
}
if( cnt!=data[hdr+7] ){
checkAppendMsg(pCheck, 0,
"Fragmented space is %d byte reported as %d on page %d",
cnt, data[hdr+7], iPage);
}
}
check_page_abort:
if (hit) sqlite3PageFree(hit);
releasePage(pPage);
return depth+1;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** This routine does a complete check of the given BTree file. aRoot[] is
** an array of pages numbers were each page number is the root page of
** a table. nRoot is the number of entries in aRoot.
**
** Write the number of error seen in *pnErr. Except for some memory
** allocation errors, an error message held in memory obtained from
** malloc is returned if *pnErr is non-zero. If *pnErr==0 then NULL is
** returned. If a memory allocation error occurs, NULL is returned.
*/
char *sqlite3BtreeIntegrityCheck(
Btree *p, /* The btree to be checked */
int *aRoot, /* An array of root pages numbers for individual trees */
int nRoot, /* Number of entries in aRoot[] */
int mxErr, /* Stop reporting errors after this many */
int *pnErr /* Write number of errors seen to this variable */
){
Pgno i;
int nRef;
IntegrityCk sCheck;
BtShared *pBt = p->pBt;
char zErr[100];
sqlite3BtreeEnter(p);
pBt->db = p->db;
nRef = sqlite3PagerRefcount(pBt->pPager);
if( lockBtreeWithRetry(p)!=SQLITE_OK ){
*pnErr = 1;
sqlite3BtreeLeave(p);
return sqlite3DbStrDup(0, "cannot acquire a read lock on the database");
}
sCheck.pBt = pBt;
sCheck.pPager = pBt->pPager;
sCheck.nPage = pagerPagecount(sCheck.pBt);
sCheck.mxErr = mxErr;
sCheck.nErr = 0;
sCheck.mallocFailed = 0;
*pnErr = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->nTrunc!=0 ){
sCheck.nPage = pBt->nTrunc;
}
#endif
if( sCheck.nPage==0 ){
unlockBtreeIfUnused(pBt);
sqlite3BtreeLeave(p);
return 0;
}
sCheck.anRef = sqlite3Malloc( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
if( !sCheck.anRef ){
unlockBtreeIfUnused(pBt);
*pnErr = 1;
sqlite3BtreeLeave(p);
return 0;
}
for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
i = PENDING_BYTE_PAGE(pBt);
if( i<=sCheck.nPage ){
sCheck.anRef[i] = 1;
}
sqlite3StrAccumInit(&sCheck.errMsg, zErr, sizeof(zErr), 20000);
/* Check the integrity of the freelist
*/
checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");
/* Check all the tables.
*/
for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
if( aRoot[i]==0 ) continue;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum && aRoot[i]>1 ){
checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0, 0);
}
#endif
checkTreePage(&sCheck, aRoot[i], "List of tree roots: ");
}
/* Make sure every page in the file is referenced
*/
for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
#ifdef SQLITE_OMIT_AUTOVACUUM
if( sCheck.anRef[i]==0 ){
checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
}
#else
/* If the database supports auto-vacuum, make sure no tables contain
** references to pointer-map pages.
*/
if( sCheck.anRef[i]==0 &&
(PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
}
if( sCheck.anRef[i]!=0 &&
(PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
checkAppendMsg(&sCheck, 0, "Pointer map page %d is referenced", i);
}
#endif
}
/* Make sure this analysis did not leave any unref() pages
*/
unlockBtreeIfUnused(pBt);
if( nRef != sqlite3PagerRefcount(pBt->pPager) ){
checkAppendMsg(&sCheck, 0,
"Outstanding page count goes from %d to %d during this analysis",
nRef, sqlite3PagerRefcount(pBt->pPager)
);
}
/* Clean up and report errors.
*/
sqlite3BtreeLeave(p);
sqlite3_free(sCheck.anRef);
if( sCheck.mallocFailed ){
sqlite3StrAccumReset(&sCheck.errMsg);
*pnErr = sCheck.nErr+1;
return 0;
}
*pnErr = sCheck.nErr;
if( sCheck.nErr==0 ) sqlite3StrAccumReset(&sCheck.errMsg);
return sqlite3StrAccumFinish(&sCheck.errMsg);
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
/*
** Return the full pathname of the underlying database file.
**
** The pager filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerFilename(p->pBt->pPager);
}
/*
** Return the pathname of the directory that contains the database file.
**
** The pager directory name is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetDirname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerDirname(p->pBt->pPager);
}
/*
** Return the pathname of the journal file for this database. The return
** value of this routine is the same regardless of whether the journal file
** has been created or not.
**
** The pager journal filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetJournalname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerJournalname(p->pBt->pPager);
}
#ifndef SQLITE_OMIT_VACUUM
/*
** Copy the complete content of pBtFrom into pBtTo. A transaction
** must be active for both files.
**
** The size of file pTo may be reduced by this operation.
** If anything goes wrong, the transaction on pTo is rolled back.
**
** If successful, CommitPhaseOne() may be called on pTo before returning.
** The caller should finish committing the transaction on pTo by calling
** sqlite3BtreeCommit().
*/
static int btreeCopyFile(Btree *pTo, Btree *pFrom){
int rc = SQLITE_OK;
Pgno i;
Pgno nFromPage; /* Number of pages in pFrom */
Pgno nToPage; /* Number of pages in pTo */
Pgno nNewPage; /* Number of pages in pTo after the copy */
Pgno iSkip; /* Pending byte page in pTo */
int nToPageSize; /* Page size of pTo in bytes */
int nFromPageSize; /* Page size of pFrom in bytes */
BtShared *pBtTo = pTo->pBt;
BtShared *pBtFrom = pFrom->pBt;
pBtTo->db = pTo->db;
pBtFrom->db = pFrom->db;
nToPageSize = pBtTo->pageSize;
nFromPageSize = pBtFrom->pageSize;
if( pTo->inTrans!=TRANS_WRITE || pFrom->inTrans!=TRANS_WRITE ){
return SQLITE_ERROR;
}
if( pBtTo->pCursor ){
return SQLITE_BUSY;
}
nToPage = pagerPagecount(pBtTo);
nFromPage = pagerPagecount(pBtFrom);
iSkip = PENDING_BYTE_PAGE(pBtTo);
/* Variable nNewPage is the number of pages required to store the
** contents of pFrom using the current page-size of pTo.
*/
nNewPage = ((i64)nFromPage * (i64)nFromPageSize + (i64)nToPageSize - 1) /
(i64)nToPageSize;
for(i=1; rc==SQLITE_OK && (i<=nToPage || i<=nNewPage); i++){
/* Journal the original page.
**
** iSkip is the page number of the locking page (PENDING_BYTE_PAGE)
** in database *pTo (before the copy). This page is never written
** into the journal file. Unless i==iSkip or the page was not
** present in pTo before the copy operation, journal page i from pTo.
*/
if( i!=iSkip && i<=nToPage ){
DbPage *pDbPage = 0;
rc = sqlite3PagerGet(pBtTo->pPager, i, &pDbPage);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pDbPage);
if( rc==SQLITE_OK && i>nFromPage ){
/* Yeah. It seems wierd to call DontWrite() right after Write(). But
** that is because the names of those procedures do not exactly
** represent what they do. Write() really means "put this page in the
** rollback journal and mark it as dirty so that it will be written
** to the database file later." DontWrite() undoes the second part of
** that and prevents the page from being written to the database. The
** page is still on the rollback journal, though. And that is the
** whole point of this block: to put pages on the rollback journal.
*/
rc = sqlite3PagerDontWrite(pDbPage);
}
sqlite3PagerUnref(pDbPage);
}
}
/* Overwrite the data in page i of the target database */
if( rc==SQLITE_OK && i!=iSkip && i<=nNewPage ){
DbPage *pToPage = 0;
sqlite3_int64 iOff;
rc = sqlite3PagerGet(pBtTo->pPager, i, &pToPage);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pToPage);
}
for(
iOff=(i-1)*nToPageSize;
rc==SQLITE_OK && iOff<i*nToPageSize;
iOff += nFromPageSize
){
DbPage *pFromPage = 0;
Pgno iFrom = (iOff/nFromPageSize)+1;
if( iFrom==PENDING_BYTE_PAGE(pBtFrom) ){
continue;
}
rc = sqlite3PagerGet(pBtFrom->pPager, iFrom, &pFromPage);
if( rc==SQLITE_OK ){
char *zTo = sqlite3PagerGetData(pToPage);
char *zFrom = sqlite3PagerGetData(pFromPage);
int nCopy;
if( nFromPageSize>=nToPageSize ){
zFrom += ((i-1)*nToPageSize - ((iFrom-1)*nFromPageSize));
nCopy = nToPageSize;
}else{
zTo += (((iFrom-1)*nFromPageSize) - (i-1)*nToPageSize);
nCopy = nFromPageSize;
}
memcpy(zTo, zFrom, nCopy);
sqlite3PagerUnref(pFromPage);
}
}
if( pToPage ){
MemPage *p = (MemPage *)sqlite3PagerGetExtra(pToPage);
p->isInit = 0;
sqlite3PagerUnref(pToPage);
}
}
}
/* If things have worked so far, the database file may need to be
** truncated. The complex part is that it may need to be truncated to
** a size that is not an integer multiple of nToPageSize - the current
** page size used by the pager associated with B-Tree pTo.
**
** For example, say the page-size of pTo is 2048 bytes and the original
** number of pages is 5 (10 KB file). If pFrom has a page size of 1024
** bytes and 9 pages, then the file needs to be truncated to 9KB.
*/
if( rc==SQLITE_OK ){
if( nFromPageSize!=nToPageSize ){
sqlite3_file *pFile = sqlite3PagerFile(pBtTo->pPager);
i64 iSize = (i64)nFromPageSize * (i64)nFromPage;
i64 iNow = (i64)((nToPage>nNewPage)?nToPage:nNewPage) * (i64)nToPageSize;
i64 iPending = ((i64)PENDING_BYTE_PAGE(pBtTo)-1) *(i64)nToPageSize;
assert( iSize<=iNow );
/* Commit phase one syncs the journal file associated with pTo
** containing the original data. It does not sync the database file
** itself. After doing this it is safe to use OsTruncate() and other
** file APIs on the database file directly.
*/
pBtTo->db = pTo->db;
rc = sqlite3PagerCommitPhaseOne(pBtTo->pPager, 0, 0, 1);
if( iSize<iNow && rc==SQLITE_OK ){
rc = sqlite3OsTruncate(pFile, iSize);
}
/* The loop that copied data from database pFrom to pTo did not
** populate the locking page of database pTo. If the page-size of
** pFrom is smaller than that of pTo, this means some data will
** not have been copied.
**
** This block copies the missing data from database pFrom to pTo
** using file APIs. This is safe because at this point we know that
** all of the original data from pTo has been synced into the
** journal file. At this point it would be safe to do anything at
** all to the database file except truncate it to zero bytes.
*/
if( rc==SQLITE_OK && nFromPageSize<nToPageSize && iSize>iPending){
i64 iOff;
for(
iOff=iPending;
rc==SQLITE_OK && iOff<(iPending+nToPageSize);
iOff += nFromPageSize
){
DbPage *pFromPage = 0;
Pgno iFrom = (iOff/nFromPageSize)+1;
if( iFrom==PENDING_BYTE_PAGE(pBtFrom) || iFrom>nFromPage ){
continue;
}
rc = sqlite3PagerGet(pBtFrom->pPager, iFrom, &pFromPage);
if( rc==SQLITE_OK ){
char *zFrom = sqlite3PagerGetData(pFromPage);
rc = sqlite3OsWrite(pFile, zFrom, nFromPageSize, iOff);
sqlite3PagerUnref(pFromPage);
}
}
}
/* Sync the database file */
if( rc==SQLITE_OK ){
rc = sqlite3PagerSync(pBtTo->pPager);
}
}else{
rc = sqlite3PagerTruncate(pBtTo->pPager, nNewPage);
}
if( rc==SQLITE_OK ){
pBtTo->pageSizeFixed = 0;
}
}
if( rc ){
sqlite3BtreeRollback(pTo);
}
return rc;
}
int sqlite3BtreeCopyFile(Btree *pTo, Btree *pFrom){
int rc;
sqlite3BtreeEnter(pTo);
sqlite3BtreeEnter(pFrom);
rc = btreeCopyFile(pTo, pFrom);
sqlite3BtreeLeave(pFrom);
sqlite3BtreeLeave(pTo);
return rc;
}
#endif /* SQLITE_OMIT_VACUUM */
/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *p){
assert( p==0 || sqlite3_mutex_held(p->db->mutex) );
return (p && (p->inTrans==TRANS_WRITE));
}
/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *p){
assert( sqlite3BtreeHoldsMutex(p) );
return (p->pBt && p->pBt->inStmt);
}
/*
** Return non-zero if a read (or write) transaction is active.
*/
int sqlite3BtreeIsInReadTrans(Btree *p){
assert( sqlite3_mutex_held(p->db->mutex) );
return (p && (p->inTrans!=TRANS_NONE));
}
/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for its own
** purposes (for example, to store a high-level schema associated with
** the shared-btree). The btree layer manages reference counting issues.
**
** The first time this is called on a shared-btree, nBytes bytes of memory
** are allocated, zeroed, and returned to the caller. For each subsequent
** call the nBytes parameter is ignored and a pointer to the same blob
** of memory returned.
**
** If the nBytes parameter is 0 and the blob of memory has not yet been
** allocated, a null pointer is returned. If the blob has already been
** allocated, it is returned as normal.
**
** Just before the shared-btree is closed, the function passed as the
** xFree argument when the memory allocation was made is invoked on the
** blob of allocated memory. This function should not call sqlite3_free()
** on the memory, the btree layer does that.
*/
void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( !pBt->pSchema && nBytes ){
pBt->pSchema = sqlite3MallocZero(nBytes);
pBt->xFreeSchema = xFree;
}
sqlite3BtreeLeave(p);
return pBt->pSchema;
}
/*
** Return true if another user of the same shared btree as the argument
** handle holds an exclusive lock on the sqlite_master table.
*/
int sqlite3BtreeSchemaLocked(Btree *p){
int rc;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
rc = (queryTableLock(p, MASTER_ROOT, READ_LOCK)!=SQLITE_OK);
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Obtain a lock on the table whose root page is iTab. The
** lock is a write lock if isWritelock is true or a read lock
** if it is false.
*/
int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
int rc = SQLITE_OK;
if( p->sharable ){
u8 lockType = READ_LOCK + isWriteLock;
assert( READ_LOCK+1==WRITE_LOCK );
assert( isWriteLock==0 || isWriteLock==1 );
sqlite3BtreeEnter(p);
rc = queryTableLock(p, iTab, lockType);
if( rc==SQLITE_OK ){
rc = lockTable(p, iTab, lockType);
}
sqlite3BtreeLeave(p);
}
return rc;
}
#endif
#ifndef SQLITE_OMIT_INCRBLOB
/*
** Argument pCsr must be a cursor opened for writing on an
** INTKEY table currently pointing at a valid table entry.
** This function modifies the data stored as part of that entry.
** Only the data content may only be modified, it is not possible
** to change the length of the data stored.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
assert( cursorHoldsMutex(pCsr) );
assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
assert(pCsr->isIncrblobHandle);
restoreCursorPosition(pCsr);
assert( pCsr->eState!=CURSOR_REQUIRESEEK );
if( pCsr->eState!=CURSOR_VALID ){
return SQLITE_ABORT;
}
/* Check some preconditions:
** (a) the cursor is open for writing,
** (b) there is no read-lock on the table being modified and
** (c) the cursor points at a valid row of an intKey table.
*/
if( !pCsr->wrFlag ){
return SQLITE_READONLY;
}
assert( !pCsr->pBt->readOnly
&& pCsr->pBt->inTransaction==TRANS_WRITE );
if( checkReadLocks(pCsr->pBtree, pCsr->pgnoRoot, pCsr, 0) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
if( pCsr->eState==CURSOR_INVALID || !pCsr->apPage[pCsr->iPage]->intKey ){
return SQLITE_ERROR;
}
return accessPayload(pCsr, offset, amt, (unsigned char *)z, 0, 1);
}
/*
** Set a flag on this cursor to cache the locations of pages from the
** overflow list for the current row. This is used by cursors opened
** for incremental blob IO only.
**
** This function sets a flag only. The actual page location cache
** (stored in BtCursor.aOverflow[]) is allocated and used by function
** accessPayload() (the worker function for sqlite3BtreeData() and
** sqlite3BtreePutData()).
*/
void sqlite3BtreeCacheOverflow(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
assert(!pCur->isIncrblobHandle);
assert(!pCur->aOverflow);
pCur->isIncrblobHandle = 1;
}
#endif