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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 1.290 2006/01/11 14:09:31 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
** "Sorting And Searching", pages 473-480. Addison-Wesley
** Publishing Company, Reading, Massachusetts.
**
** The basic idea is that each page of the file contains N database
** entries and N+1 pointers to subpages.
**
** ----------------------------------------------------------------
** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N) | Ptr(N+1) |
** ----------------------------------------------------------------
**
** All of the keys on the page that Ptr(0) points to have values less
** than Key(0). All of the keys on page Ptr(1) and its subpages have
** values greater than Key(0) and less than Key(1). All of the keys
** on Ptr(N+1) and its subpages have values greater than Key(N). And
** so forth.
**
** Finding a particular key requires reading O(log(M)) pages from the
** disk where M is the number of entries in the tree.
**
** In this implementation, a single file can hold one or more separate
** BTrees. Each BTree is identified by the index of its root page. The
** key and data for any entry are combined to form the "payload". A
** fixed amount of payload can be carried directly on the database
** page. If the payload is larger than the preset amount then surplus
** bytes are stored on overflow pages. The payload for an entry
** and the preceding pointer are combined to form a "Cell". Each
** page has a small header which contains the Ptr(N+1) pointer and other
** information such as the size of key and data.
**
** FORMAT DETAILS
**
** The file is divided into pages. The first page is called page 1,
** the second is page 2, and so forth. A page number of zero indicates
** "no such page". The page size can be anything between 512 and 65536.
** Each page can be either a btree page, a freelist page or an overflow
** page.
**
** The first page is always a btree page. The first 100 bytes of the first
** page contain a special header (the "file header") that describes the file.
** The format of the file header is as follows:
**
** OFFSET SIZE DESCRIPTION
** 0 16 Header string: "SQLite format 3\000"
** 16 2 Page size in bytes.
** 18 1 File format write version
** 19 1 File format read version
** 20 1 Bytes of unused space at the end of each page
** 21 1 Max embedded payload fraction
** 22 1 Min embedded payload fraction
** 23 1 Min leaf payload fraction
** 24 4 File change counter
** 28 4 Reserved for future use
** 32 4 First freelist page
** 36 4 Number of freelist pages in the file
** 40 60 15 4-byte meta values passed to higher layers
**
** All of the integer values are big-endian (most significant byte first).
**
** The file change counter is incremented when the database is changed more
** than once within the same second. This counter, together with the
** modification time of the file, allows other processes to know
** when the file has changed and thus when they need to flush their
** cache.
**
** The max embedded payload fraction is the amount of the total usable
** space in a page that can be consumed by a single cell for standard
** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default
** is to limit the maximum cell size so that at least 4 cells will fit
** on one page. Thus the default max embedded payload fraction is 64.
**
** If the payload for a cell is larger than the max payload, then extra
** payload is spilled to overflow pages. Once an overflow page is allocated,
** as many bytes as possible are moved into the overflow pages without letting
** the cell size drop below the min embedded payload fraction.
**
** The min leaf payload fraction is like the min embedded payload fraction
** except that it applies to leaf nodes in a LEAFDATA tree. The maximum
** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
** not specified in the header.
**
** Each btree pages is divided into three sections: The header, the
** cell pointer array, and the cell area area. Page 1 also has a 100-byte
** file header that occurs before the page header.
**
** |----------------|
** | file header | 100 bytes. Page 1 only.
** |----------------|
** | page header | 8 bytes for leaves. 12 bytes for interior nodes
** |----------------|
** | cell pointer | | 2 bytes per cell. Sorted order.
** | array | | Grows downward
** | | v
** |----------------|
** | unallocated |
** | space |
** |----------------| ^ Grows upwards
** | cell content | | Arbitrary order interspersed with freeblocks.
** | area | | and free space fragments.
** |----------------|
**
** The page headers looks like this:
**
** OFFSET SIZE DESCRIPTION
** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
** 1 2 byte offset to the first freeblock
** 3 2 number of cells on this page
** 5 2 first byte of the cell content area
** 7 1 number of fragmented free bytes
** 8 4 Right child (the Ptr(N+1) value). Omitted on leaves.
**
** The flags define the format of this btree page. The leaf flag means that
** this page has no children. The zerodata flag means that this page carries
** only keys and no data. The intkey flag means that the key is a integer
** which is stored in the key size entry of the cell header rather than in
** the payload area.
**
** The cell pointer array begins on the first byte after the page header.
** The cell pointer array contains zero or more 2-byte numbers which are
** offsets from the beginning of the page to the cell content in the cell
** content area. The cell pointers occur in sorted order. The system strives
** to keep free space after the last cell pointer so that new cells can
** be easily added without having to defragment the page.
**
** Cell content is stored at the very end of the page and grows toward the
** beginning of the page.
**
** Unused space within the cell content area is collected into a linked list of
** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset
** to the first freeblock is given in the header. Freeblocks occur in
** increasing order. Because a freeblock must be at least 4 bytes in size,
** any group of 3 or fewer unused bytes in the cell content area cannot
** exist on the freeblock chain. A group of 3 or fewer free bytes is called
** a fragment. The total number of bytes in all fragments is recorded.
** in the page header at offset 7.
**
** SIZE DESCRIPTION
** 2 Byte offset of the next freeblock
** 2 Bytes in this freeblock
**
** Cells are of variable length. Cells are stored in the cell content area at
** the end of the page. Pointers to the cells are in the cell pointer array
** that immediately follows the page header. Cells is not necessarily
** contiguous or in order, but cell pointers are contiguous and in order.
**
** Cell content makes use of variable length integers. A variable
** length integer is 1 to 9 bytes where the lower 7 bits of each
** byte are used. The integer consists of all bytes that have bit 8 set and
** the first byte with bit 8 clear. The most significant byte of the integer
** appears first. A variable-length integer may not be more than 9 bytes long.
** As a special case, all 8 bytes of the 9th byte are used as data. This
** allows a 64-bit integer to be encoded in 9 bytes.
**
** 0x00 becomes 0x00000000
** 0x7f becomes 0x0000007f
** 0x81 0x00 becomes 0x00000080
** 0x82 0x00 becomes 0x00000100
** 0x80 0x7f becomes 0x0000007f
** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678
** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081
**
** Variable length integers are used for rowids and to hold the number of
** bytes of key and data in a btree cell.
**
** The content of a cell looks like this:
**
** SIZE DESCRIPTION
** 4 Page number of the left child. Omitted if leaf flag is set.
** var Number of bytes of data. Omitted if the zerodata flag is set.
** var Number of bytes of key. Or the key itself if intkey flag is set.
** * Payload
** 4 First page of the overflow chain. Omitted if no overflow
**
** Overflow pages form a linked list. Each page except the last is completely
** filled with data (pagesize - 4 bytes). The last page can have as little
** as 1 byte of data.
**
** SIZE DESCRIPTION
** 4 Page number of next overflow page
** * Data
**
** Freelist pages come in two subtypes: trunk pages and leaf pages. The
** file header points to first in a linked list of trunk page. Each trunk
** page points to multiple leaf pages. The content of a leaf page is
** unspecified. A trunk page looks like this:
**
** SIZE DESCRIPTION
** 4 Page number of next trunk page
** 4 Number of leaf pointers on this page
** * zero or more pages numbers of leaves
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "os.h"
#include <assert.h>
/* Round up a number to the next larger multiple of 8. This is used
** to force 8-byte alignment on 64-bit architectures.
*/
#define ROUND8(x) ((x+7)&~7)
/* The following value is the maximum cell size assuming a maximum page
** size give above.
*/
#define MX_CELL_SIZE(pBt) (pBt->pageSize-8)
/* The maximum number of cells on a single page of the database. This
** assumes a minimum cell size of 3 bytes. Such small cells will be
** exceedingly rare, but they are possible.
*/
#define MX_CELL(pBt) ((pBt->pageSize-8)/3)
/* Forward declarations */
typedef struct MemPage MemPage;
typedef struct BtLock BtLock;
/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the file as a real database.
**
** You can change this value at compile-time by specifying a
** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The
** header must be exactly 16 bytes including the zero-terminator so
** the string itself should be 15 characters long. If you change
** the header, then your custom library will not be able to read
** databases generated by the standard tools and the standard tools
** will not be able to read databases created by your custom library.
*/
#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
# define SQLITE_FILE_HEADER "SQLite format 3"
#endif
static const char zMagicHeader[] = SQLITE_FILE_HEADER;
/*
** Page type flags. An ORed combination of these flags appear as the
** first byte of every BTree page.
*/
#define PTF_INTKEY 0x01
#define PTF_ZERODATA 0x02
#define PTF_LEAFDATA 0x04
#define PTF_LEAF 0x08
/*
** As each page of the file is loaded into memory, an instance of the following
** structure is appended and initialized to zero. This structure stores
** information about the page that is decoded from the raw file page.
**
** The pParent field points back to the parent page. This allows us to
** walk up the BTree from any leaf to the root. Care must be taken to
** unref() the parent page pointer when this page is no longer referenced.
** The pageDestructor() routine handles that chore.
*/
struct MemPage {
u8 isInit; /* True if previously initialized. MUST BE FIRST! */
u8 idxShift; /* True if Cell indices have changed */
u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
u8 intKey; /* True if intkey flag is set */
u8 leaf; /* True if leaf flag is set */
u8 zeroData; /* True if table stores keys only */
u8 leafData; /* True if tables stores data on leaves only */
u8 hasData; /* True if this page stores data */
u8 hdrOffset; /* 100 for page 1. 0 otherwise */
u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
u16 maxLocal; /* Copy of Btree.maxLocal or Btree.maxLeaf */
u16 minLocal; /* Copy of Btree.minLocal or Btree.minLeaf */
u16 cellOffset; /* Index in aData of first cell pointer */
u16 idxParent; /* Index in parent of this node */
u16 nFree; /* Number of free bytes on the page */
u16 nCell; /* Number of cells on this page, local and ovfl */
struct _OvflCell { /* Cells that will not fit on aData[] */
u8 *pCell; /* Pointers to the body of the overflow cell */
u16 idx; /* Insert this cell before idx-th non-overflow cell */
} aOvfl[5];
BtShared *pBt; /* Pointer back to BTree structure */
u8 *aData; /* Pointer back to the start of the page */
Pgno pgno; /* Page number for this page */
MemPage *pParent; /* The parent of this page. NULL for root */
};
/*
** The in-memory image of a disk page has the auxiliary information appended
** to the end. EXTRA_SIZE is the number of bytes of space needed to hold
** that extra information.
*/
#define EXTRA_SIZE sizeof(MemPage)
/* Btree handle */
struct Btree {
sqlite3 *pSqlite;
BtShared *pBt;
u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
};
/*
** Btree.inTrans may take one of the following values.
**
** If the shared-data extension is enabled, there may be multiple users
** of the Btree structure. At most one of these may open a write transaction,
** but any number may have active read transactions. Variable Btree.pDb
** points to the handle that owns any current write-transaction.
*/
#define TRANS_NONE 0
#define TRANS_READ 1
#define TRANS_WRITE 2
/*
** Everything we need to know about an open database
*/
struct BtShared {
Pager *pPager; /* The page cache */
BtCursor *pCursor; /* A list of all open cursors */
MemPage *pPage1; /* First page of the database */
u8 inStmt; /* True if we are in a statement subtransaction */
u8 readOnly; /* True if the underlying file is readonly */
u8 maxEmbedFrac; /* Maximum payload as % of total page size */
u8 minEmbedFrac; /* Minimum payload as % of total page size */
u8 minLeafFrac; /* Minimum leaf payload as % of total page size */
u8 pageSizeFixed; /* True if the page size can no longer be changed */
#ifndef SQLITE_OMIT_AUTOVACUUM
u8 autoVacuum; /* True if database supports auto-vacuum */
#endif
u16 pageSize; /* Total number of bytes on a page */
u16 usableSize; /* Number of usable bytes on each page */
int maxLocal; /* Maximum local payload in non-LEAFDATA tables */
int minLocal; /* Minimum local payload in non-LEAFDATA tables */
int maxLeaf; /* Maximum local payload in a LEAFDATA table */
int minLeaf; /* Minimum local payload in a LEAFDATA table */
BusyHandler *pBusyHandler; /* Callback for when there is lock contention */
u8 inTransaction; /* Transaction state */
int nRef; /* Number of references to this structure */
int nTransaction; /* Number of open transactions (read + write) */
void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */
#ifndef SQLITE_OMIT_SHARED_CACHE
BtLock *pLock; /* List of locks held on this shared-btree struct */
BtShared *pNext; /* Next in ThreadData.pBtree linked list */
#endif
};
/*
** An instance of the following structure is used to hold information
** about a cell. The parseCellPtr() function fills in this structure
** based on information extract from the raw disk page.
*/
typedef struct CellInfo CellInfo;
struct CellInfo {
u8 *pCell; /* Pointer to the start of cell content */
i64 nKey; /* The key for INTKEY tables, or number of bytes in key */
u32 nData; /* Number of bytes of data */
u16 nHeader; /* Size of the cell content header in bytes */
u16 nLocal; /* Amount of payload held locally */
u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */
u16 nSize; /* Size of the cell content on the main b-tree page */
};
/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
** MemPage.aCell[] of the entry.
*/
struct BtCursor {
Btree *pBtree; /* The Btree to which this cursor belongs */
BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */
int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */
void *pArg; /* First arg to xCompare() */
Pgno pgnoRoot; /* The root page of this tree */
MemPage *pPage; /* Page that contains the entry */
int idx; /* Index of the entry in pPage->aCell[] */
CellInfo info; /* A parse of the cell we are pointing at */
u8 wrFlag; /* True if writable */
u8 eState; /* One of the CURSOR_XXX constants (see below) */
#ifndef SQLITE_OMIT_SHARED_CACHE
void *pKey;
i64 nKey;
int skip; /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
#endif
};
/*
** Potential values for BtCursor.eState. The first two values (VALID and
** INVALID) may occur in any build. The third (REQUIRESEEK) may only occur
** if sqlite was compiled without the OMIT_SHARED_CACHE symbol defined.
**
** CURSOR_VALID:
** Cursor points to a valid entry. getPayload() etc. may be called.
**
** CURSOR_INVALID:
** Cursor does not point to a valid entry. This can happen (for example)
** because the table is empty or because BtreeCursorFirst() has not been
** called.
**
** CURSOR_REQUIRESEEK:
** The table that this cursor was opened on still exists, but has been
** modified since the cursor was last used. The cursor position is saved
** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
** this state, restoreCursorPosition() can be called to attempt to seek
** the cursor to the saved position.
*/
#define CURSOR_INVALID 0
#define CURSOR_VALID 1
#define CURSOR_REQUIRESEEK 2
/*
** The TRACE macro will print high-level status information about the
** btree operation when the global variable sqlite3_btree_trace is
** enabled.
*/
#if SQLITE_TEST
# define TRACE(X) if( sqlite3_btree_trace )\
{ sqlite3DebugPrintf X; fflush(stdout); }
#else
# define TRACE(X)
#endif
int sqlite3_btree_trace=0; /* True to enable tracing */
/*
** Forward declaration
*/
static int checkReadLocks(BtShared*,Pgno,BtCursor*);
/*
** Read or write a two- and four-byte big-endian integer values.
*/
static u32 get2byte(unsigned char *p){
return (p[0]<<8) | p[1];
}
static u32 get4byte(unsigned char *p){
return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
}
static void put2byte(unsigned char *p, u32 v){
p[0] = v>>8;
p[1] = v;
}
static void put4byte(unsigned char *p, u32 v){
p[0] = v>>24;
p[1] = v>>16;
p[2] = v>>8;
p[3] = v;
}
/*
** Routines to read and write variable-length integers. These used to
** be defined locally, but now we use the varint routines in the util.c
** file.
*/
#define getVarint sqlite3GetVarint
#define getVarint32 sqlite3GetVarint32
#define putVarint sqlite3PutVarint
/* The database page the PENDING_BYTE occupies. This page is never used.
** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They
** should possibly be consolidated (presumably in pager.h).
*/
#define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)
/*
** A linked list of the following structures is stored at BtShared.pLock.
** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
** is opened on the table with root page BtShared.iTable. Locks are removed
** from this list when a transaction is committed or rolled back, or when
** a btree handle is closed.
*/
struct BtLock {
Btree *pBtree; /* Btree handle holding this lock */
Pgno iTable; /* Root page of table */
u8 eLock; /* READ_LOCK or WRITE_LOCK */
BtLock *pNext; /* Next in BtShared.pLock list */
};
/* Candidate values for BtLock.eLock */
#define READ_LOCK 1
#define WRITE_LOCK 2
#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)
#define restoreCursorPosition(a,b) SQLITE_OK
#define saveAllCursors(a,b,c) SQLITE_OK
#else
/*
** 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 = SQLITE_OK;
assert( CURSOR_VALID==pCur->eState|| CURSOR_INVALID==pCur->eState );
assert( 0==pCur->pKey );
if( pCur->eState==CURSOR_VALID ){
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->pPage->intKey){
void *pKey = sqliteMalloc(pCur->nKey);
if( pKey ){
rc = sqlite3BtreeKey(pCur, 0, pCur->nKey, pKey);
if( rc==SQLITE_OK ){
pCur->pKey = pKey;
}else{
sqliteFree(pKey);
}
}else{
rc = SQLITE_NOMEM;
}
}
assert( !pCur->pPage->intKey || !pCur->pKey );
/* Todo: Should we drop the reference to pCur->pPage here? */
if( rc==SQLITE_OK ){
pCur->eState = CURSOR_REQUIRESEEK;
}
}
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;
if( sqlite3ThreadData()->useSharedData ){
for(p=pBt->pCursor; p; p=p->pNext){
if( p!=pExcept && p->pgnoRoot==iRoot && p->eState==CURSOR_VALID ){
int rc = saveCursorPosition(p);
if( SQLITE_OK!=rc ){
return rc;
}
}
}
}
return SQLITE_OK;
}
/*
** 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().
**
** If the second argument argument - doSeek - is false, then instead of
** returning the cursor to it's saved position, any saved position is deleted
** and the cursor state set to CURSOR_INVALID.
*/
static int restoreCursorPosition(BtCursor *pCur, int doSeek){
int rc = SQLITE_OK;
if( pCur->eState==CURSOR_REQUIRESEEK ){
assert( sqlite3ThreadData()->useSharedData );
if( doSeek ){
rc = sqlite3BtreeMoveto(pCur, pCur->pKey, pCur->nKey, &pCur->skip);
}else{
pCur->eState = CURSOR_INVALID;
}
if( rc==SQLITE_OK ){
sqliteFree(pCur->pKey);
pCur->pKey = 0;
assert( CURSOR_VALID==pCur->eState || CURSOR_INVALID==pCur->eState );
}
}
return rc;
}
/*
** 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;
/* This is a no-op if the shared-cache is not enabled */
if( 0==sqlite3ThreadData()->useSharedData ){
return SQLITE_OK;
}
/* 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(
!p->pSqlite ||
0==(p->pSqlite->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;
}
/*
** 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;
/* This is a no-op if the shared-cache is not enabled */
if( 0==sqlite3ThreadData()->useSharedData ){
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->pSqlite) &&
(p->pSqlite->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 *)sqliteMalloc(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;
}
/*
** Release all the table locks (locks obtained via calls to the lockTable()
** procedure) held by Btree handle p.
*/
static void unlockAllTables(Btree *p){
BtLock **ppIter = &p->pBt->pLock;
/* If the shared-cache extension is not enabled, there should be no
** locks in the BtShared.pLock list, making this procedure a no-op. Assert
** that this is the case.
*/
assert( sqlite3ThreadData()->useSharedData || 0==*ppIter );
while( *ppIter ){
BtLock *pLock = *ppIter;
if( pLock->pBtree==p ){
*ppIter = pLock->pNext;
sqliteFree(pLock);
}else{
ppIter = &pLock->pNext;
}
}
}
#endif /* SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** These macros define the location of the pointer-map entry for a
** database page. The first argument to each is the number of usable
** bytes on each page of the database (often 1024). The second is the
** page number to look up in the pointer map.
**
** PTRMAP_PAGENO returns the database page number of the pointer-map
** page that stores the required pointer. PTRMAP_PTROFFSET returns
** the offset of the requested map entry.
**
** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
** this test.
*/
#define PTRMAP_PAGENO(pgsz, pgno) (((pgno-2)/(pgsz/5+1))*(pgsz/5+1)+2)
#define PTRMAP_PTROFFSET(pgsz, pgno) (((pgno-2)%(pgsz/5+1)-1)*5)
#define PTRMAP_ISPAGE(pgsz, pgno) (PTRMAP_PAGENO(pgsz,pgno)==pgno)
/*
** The pointer map is a lookup table that identifies the parent page for
** each child page in the database file. The parent page is the page that
** contains a pointer to the child. Every page in the database contains
** 0 or 1 parent pages. (In this context 'database page' refers
** to any page that is not part of the pointer map itself.) Each pointer map
** entry consists of a single byte 'type' and a 4 byte parent page number.
** The PTRMAP_XXX identifiers below are the valid types.
**
** The purpose of the pointer map is to facility moving pages from one
** position in the file to another as part of autovacuum. When a page
** is moved, the pointer in its parent must be updated to point to the
** new location. The pointer map is used to locate the parent page quickly.
**
** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
** used in this case.
**
** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number
** is not used in this case.
**
** PTRMAP_OVERFLOW1: The database page is the first page in a list of
** overflow pages. The page number identifies the page that
** contains the cell with a pointer to this overflow page.
**
** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
** overflow pages. The page-number identifies the previous
** page in the overflow page list.
**
** PTRMAP_BTREE: The database page is a non-root btree page. The page number
** identifies the parent page in the btree.
*/
#define PTRMAP_ROOTPAGE 1
#define PTRMAP_FREEPAGE 2
#define PTRMAP_OVERFLOW1 3
#define PTRMAP_OVERFLOW2 4
#define PTRMAP_BTREE 5
/*
** 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){
u8 *pPtrmap; /* The pointer map page */
Pgno iPtrmap; /* The pointer map page number */
int offset; /* Offset in pointer map page */
int rc;
assert( pBt->autoVacuum );
if( key==0 ){
return SQLITE_CORRUPT_BKPT;
}
iPtrmap = PTRMAP_PAGENO(pBt->usableSize, key);
rc = sqlite3pager_get(pBt->pPager, iPtrmap, (void **)&pPtrmap);
if( rc!=SQLITE_OK ){
return rc;
}
offset = PTRMAP_PTROFFSET(pBt->usableSize, key);
if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
rc = sqlite3pager_write(pPtrmap);
if( rc==SQLITE_OK ){
pPtrmap[offset] = eType;
put4byte(&pPtrmap[offset+1], parent);
}
}
sqlite3pager_unref(pPtrmap);
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){
int iPtrmap; /* Pointer map page index */
u8 *pPtrmap; /* Pointer map page data */
int offset; /* Offset of entry in pointer map */
int rc;
iPtrmap = PTRMAP_PAGENO(pBt->usableSize, key);
rc = sqlite3pager_get(pBt->pPager, iPtrmap, (void **)&pPtrmap);
if( rc!=0 ){
return rc;
}
offset = PTRMAP_PTROFFSET(pBt->usableSize, key);
if( pEType ) *pEType = pPtrmap[offset];
if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
sqlite3pager_unref(pPtrmap);
if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
return SQLITE_OK;
}
#endif /* SQLITE_OMIT_AUTOVACUUM */
/*
** 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.
*/
static u8 *findCell(MemPage *pPage, int iCell){
u8 *data = pPage->aData;
assert( iCell>=0 );
assert( iCell<get2byte(&data[pPage->hdrOffset+3]) );
return data + get2byte(&data[pPage->cellOffset+2*iCell]);
}
/*
** 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;
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. parseCell() takes a cell index
** as the second argument and parseCellPtr() takes a pointer to the
** body of the cell as its second argument.
*/
static void parseCellPtr(
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 */
pInfo->pCell = pCell;
assert( pPage->leaf==0 || pPage->leaf==1 );
n = pPage->childPtrSize;
assert( n==4-4*pPage->leaf );
if( pPage->hasData ){
n += getVarint32(&pCell[n], &nPayload);
}else{
nPayload = 0;
}
n += getVarint(&pCell[n], (u64 *)&pInfo->nKey);
pInfo->nHeader = n;
pInfo->nData = nPayload;
if( !pPage->intKey ){
nPayload += pInfo->nKey;
}
if( 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 */
pInfo->nLocal = nPayload;
pInfo->iOverflow = 0;
nSize = nPayload + n;
if( nSize<4 ){
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;
}
}
static void parseCell(
MemPage *pPage, /* Page containing the cell */
int iCell, /* The cell index. First cell is 0 */
CellInfo *pInfo /* Fill in this structure */
){
parseCellPtr(pPage, findCell(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 int cellSize(MemPage *pPage, int iCell){
CellInfo info;
parseCell(pPage, iCell, &info);
return info.nSize;
}
#endif
static int cellSizePtr(MemPage *pPage, u8 *pCell){
CellInfo info;
parseCellPtr(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){
if( pCell ){
CellInfo info;
parseCellPtr(pPage, pCell, &info);
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;
pCell = findOverflowCell(pPage, iCell);
return ptrmapPutOvflPtr(pPage, pCell);
}
#endif
/*
** Do sanity checking on a page. Throw an exception if anything is
** not right.
**
** This routine is used for internal error checking only. It is omitted
** from most builds.
*/
#if defined(BTREE_DEBUG) && !defined(NDEBUG) && 0
static void _pageIntegrity(MemPage *pPage){
int usableSize;
u8 *data;
int i, j, idx, c, pc, hdr, nFree;
int cellOffset;
int nCell, cellLimit;
u8 *used;
used = sqliteMallocRaw( pPage->pBt->pageSize );
if( used==0 ) return;
usableSize = pPage->pBt->usableSize;
assert( pPage->aData==&((unsigned char*)pPage)[-pPage->pBt->pageSize] );
hdr = pPage->hdrOffset;
assert( hdr==(pPage->pgno==1 ? 100 : 0) );
assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
c = pPage->aData[hdr];
if( pPage->isInit ){
assert( pPage->leaf == ((c & PTF_LEAF)!=0) );
assert( pPage->zeroData == ((c & PTF_ZERODATA)!=0) );
assert( pPage->leafData == ((c & PTF_LEAFDATA)!=0) );
assert( pPage->intKey == ((c & (PTF_INTKEY|PTF_LEAFDATA))!=0) );
assert( pPage->hasData ==
!(pPage->zeroData || (!pPage->leaf && pPage->leafData)) );
assert( pPage->cellOffset==pPage->hdrOffset+12-4*pPage->leaf );
assert( pPage->nCell = get2byte(&pPage->aData[hdr+3]) );
}
data = pPage->aData;
memset(used, 0, usableSize);
for(i=0; i<hdr+10-pPage->leaf*4; i++) used[i] = 1;
nFree = 0;
pc = get2byte(&data[hdr+1]);
while( pc ){
int size;
assert( pc>0 && pc<usableSize-4 );
size = get2byte(&data[pc+2]);
assert( pc+size<=usableSize );
nFree += size;
for(i=pc; i<pc+size; i++){
assert( used[i]==0 );
used[i] = 1;
}
pc = get2byte(&data[pc]);
}
idx = 0;
nCell = get2byte(&data[hdr+3]);
cellLimit = get2byte(&data[hdr+5]);
assert( pPage->isInit==0
|| pPage->nFree==nFree+data[hdr+7]+cellLimit-(cellOffset+2*nCell) );
cellOffset = pPage->cellOffset;
for(i=0; i<nCell; i++){
int size;
pc = get2byte(&data[cellOffset+2*i]);
assert( pc>0 && pc<usableSize-4 );
size = cellSize(pPage, &data[pc]);
assert( pc+size<=usableSize );
for(j=pc; j<pc+size; j++){
assert( used[j]==0 );
used[j] = 1;
}
}
for(i=cellOffset+2*nCell; i<cellimit; i++){
assert( used[i]==0 );
used[i] = 1;
}
nFree = 0;
for(i=0; i<usableSize; i++){
assert( used[i]<=1 );
if( used[i]==0 ) nFree++;
}
assert( nFree==data[hdr+7] );
sqliteFree(used);
}
#define pageIntegrity(X) _pageIntegrity(X)
#else
# define pageIntegrity(X)
#endif
/* A bunch of assert() statements to check the transaction state variables
** of handle p (type Btree*) are internally consistent.
*/
#define btreeIntegrity(p) \
assert( p->inTrans!=TRANS_NONE || p->pBt->nTransaction<p->pBt->nRef ); \
assert( p->pBt->nTransaction<=p->pBt->nRef ); \
assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
assert( p->pBt->inTransaction>=p->inTrans );
/*
** 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 brk; /* 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( sqlite3pager_iswriteable(pPage->aData) );
assert( pPage->pBt!=0 );
assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
assert( pPage->nOverflow==0 );
temp = sqliteMalloc( pPage->pBt->pageSize );
if( temp==0 ) return SQLITE_NOMEM;
data = pPage->aData;
hdr = pPage->hdrOffset;
cellOffset = pPage->cellOffset;
nCell = pPage->nCell;
assert( nCell==get2byte(&data[hdr+3]) );
usableSize = pPage->pBt->usableSize;
brk = get2byte(&data[hdr+5]);
memcpy(&temp[brk], &data[brk], usableSize - brk);
brk = usableSize;
for(i=0; i<nCell; i++){
u8 *pAddr; /* The i-th cell pointer */
pAddr = &data[cellOffset + i*2];
pc = get2byte(pAddr);
assert( pc<pPage->pBt->usableSize );
size = cellSizePtr(pPage, &temp[pc]);
brk -= size;
memcpy(&data[brk], &temp[pc], size);
put2byte(pAddr, brk);
}
assert( brk>=cellOffset+2*nCell );
put2byte(&data[hdr+5], brk);
data[hdr+1] = 0;
data[hdr+2] = 0;
data[hdr+7] = 0;
addr = cellOffset+2*nCell;
memset(&data[addr], 0, brk-addr);
sqliteFree(temp);
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. Or return 0 if there is not enough free
** space on the page to satisfy the allocation request.
**
** 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( sqlite3pager_iswriteable(data) );
assert( pPage->pBt );
if( nByte<4 ) nByte = 4;
if( pPage->nFree<nByte || pPage->nOverflow>0 ) return 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 ){
if( defragmentPage(pPage) ) return 0;
top = get2byte(&data[hdr+5]);
}
top -= nByte;
assert( cellOffset + 2*nCell <= top );
put2byte(&data[hdr+5], top);
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 void freeSpace(MemPage *pPage, int start, int size){
int addr, pbegin, hdr;
unsigned char *data = pPage->aData;
assert( pPage->pBt!=0 );
assert( sqlite3pager_iswriteable(data) );
assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
assert( (start + size)<=pPage->pBt->usableSize );
if( size<4 ) size = 4;
/* 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 );
assert( pbegin>addr );
addr = pbegin;
}
assert( pbegin<=pPage->pBt->usableSize-4 );
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);
assert( frag<=data[pPage->hdrOffset+7] );
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]));
}
}
/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
*/
static void decodeFlags(MemPage *pPage, int flagByte){
BtShared *pBt; /* A copy of pPage->pBt */
assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
pPage->intKey = (flagByte & (PTF_INTKEY|PTF_LEAFDATA))!=0;
pPage->zeroData = (flagByte & PTF_ZERODATA)!=0;
pPage->leaf = (flagByte & PTF_LEAF)!=0;
pPage->childPtrSize = 4*(pPage->leaf==0);
pBt = pPage->pBt;
if( flagByte & PTF_LEAFDATA ){
pPage->leafData = 1;
pPage->maxLocal = pBt->maxLeaf;
pPage->minLocal = pBt->minLeaf;
}else{
pPage->leafData = 0;
pPage->maxLocal = pBt->maxLocal;
pPage->minLocal = pBt->minLocal;
}
pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
}
/*
** Initialize the auxiliary information for a disk block.
**
** The pParent parameter must be a pointer to the MemPage which
** is the parent of the page being initialized. The root of a
** BTree has no parent and so for that page, pParent==NULL.
**
** 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.
*/
static int initPage(
MemPage *pPage, /* The page to be initialized */
MemPage *pParent /* The parent. Might be NULL */
){
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;
assert( pBt!=0 );
assert( pParent==0 || pParent->pBt==pBt );
assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
assert( pPage->aData == &((unsigned char*)pPage)[-pBt->pageSize] );
if( pPage->pParent!=pParent && (pPage->pParent!=0 || pPage->isInit) ){
/* The parent page should never change unless the file is corrupt */
return SQLITE_CORRUPT_BKPT;
}
if( pPage->isInit ) return SQLITE_OK;
if( pPage->pParent==0 && pParent!=0 ){
pPage->pParent = pParent;
sqlite3pager_ref(pParent->aData);
}
hdr = pPage->hdrOffset;
data = pPage->aData;
decodeFlags(pPage, data[hdr]);
pPage->nOverflow = 0;
pPage->idxShift = 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;
}
if( pPage->nCell==0 && pParent!=0 && pParent->pgno!=1 ){
/* All pages must have at least one cell, except for root pages */
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;
}
pPage->isInit = 1;
pageIntegrity(pPage);
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( sqlite3pager_pagenumber(data)==pPage->pgno );
assert( &data[pBt->pageSize] == (unsigned char*)pPage );
assert( sqlite3pager_iswriteable(data) );
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;
pPage->idxShift = 0;
pPage->nCell = 0;
pPage->isInit = 1;
pageIntegrity(pPage);
}
/*
** Get a page from the pager. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static int getPage(BtShared *pBt, Pgno pgno, MemPage **ppPage){
int rc;
unsigned char *aData;
MemPage *pPage;
rc = sqlite3pager_get(pBt->pPager, pgno, (void**)&aData);
if( rc ) return rc;
pPage = (MemPage*)&aData[pBt->pageSize];
pPage->aData = aData;
pPage->pBt = pBt;
pPage->pgno = pgno;
pPage->hdrOffset = pPage->pgno==1 ? 100 : 0;
*ppPage = pPage;
return SQLITE_OK;
}
/*
** Get a page from the pager and initialize it. This routine
** is just a convenience wrapper around separate calls to
** getPage() and initPage().
*/
static int getAndInitPage(
BtShared *pBt, /* The database file */
Pgno pgno, /* Number of the page to get */
MemPage **ppPage, /* Write the page pointer here */
MemPage *pParent /* Parent of the page */
){
int rc;
if( pgno==0 ){
return SQLITE_CORRUPT_BKPT;
}
rc = getPage(pBt, pgno, ppPage);
if( rc==SQLITE_OK && (*ppPage)->isInit==0 ){
rc = initPage(*ppPage, pParent);
}
return rc;
}
/*
** Release a MemPage. This should be called once for each prior
** call to getPage.
*/
static void releasePage(MemPage *pPage){
if( pPage ){
assert( pPage->aData );
assert( pPage->pBt );
assert( &pPage->aData[pPage->pBt->pageSize]==(unsigned char*)pPage );
sqlite3pager_unref(pPage->aData);
}
}
/*
** This routine is called when the reference count for a page
** reaches zero. We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData, int pageSize){
MemPage *pPage;
assert( (pageSize & 7)==0 );
pPage = (MemPage*)&((char*)pData)[pageSize];
if( pPage->pParent ){
MemPage *pParent = pPage->pParent;
pPage->pParent = 0;
releasePage(pParent);
}
pPage->isInit = 0;
}
/*
** 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(void *pData, int pageSize){
MemPage *pPage;
assert( (pageSize & 7)==0 );
pPage = (MemPage*)&((char*)pData)[pageSize];
if( pPage->isInit ){
pPage->isInit = 0;
initPage(pPage, pPage->pParent);
}
}
/*
** 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.
*/
int sqlite3BtreeOpen(
const char *zFilename, /* Name of the file containing the BTree database */
sqlite3 *pSqlite, /* Associated database handle */
Btree **ppBtree, /* Pointer to new Btree object written here */
int flags /* Options */
){
BtShared *pBt; /* Shared part of btree structure */
Btree *p; /* Handle to return */
int rc;
int nReserve;
unsigned char zDbHeader[100];
#ifndef SQLITE_OMIT_SHARED_CACHE
ThreadData *pTsd = sqlite3ThreadData();
#endif
/* 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 = !zFilename;
#else
const int isMemdb = !zFilename || (strcmp(zFilename, ":memory:")?0:1);
#endif
#endif
p = sqliteMalloc(sizeof(Btree));
if( !p ){
return SQLITE_NOMEM;
}
p->inTrans = TRANS_NONE;
p->pSqlite = pSqlite;
/* Try to find an existing Btree structure opened on zFilename. */
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
if( pTsd->useSharedData && zFilename && !isMemdb ){
char *zFullPathname = sqlite3OsFullPathname(zFilename);
if( !zFullPathname ){
sqliteFree(p);
return SQLITE_NOMEM;
}
for(pBt=pTsd->pBtree; pBt; pBt=pBt->pNext){
assert( pBt->nRef>0 );
if( 0==strcmp(zFullPathname, sqlite3pager_filename(pBt->pPager)) ){
p->pBt = pBt;
*ppBtree = p;
pBt->nRef++;
sqliteFree(zFullPathname);
return SQLITE_OK;
}
}
sqliteFree(zFullPathname);
}
#endif
/*
** 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 );
assert( sizeof(u64)==8 );
assert( sizeof(u32)==4 );
assert( sizeof(u16)==2 );
assert( sizeof(Pgno)==4 );
pBt = sqliteMalloc( sizeof(*pBt) );
if( pBt==0 ){
*ppBtree = 0;
sqliteFree(p);
return SQLITE_NOMEM;
}
rc = sqlite3pager_open(&pBt->pPager, zFilename, EXTRA_SIZE, flags);
if( rc!=SQLITE_OK ){
if( pBt->pPager ) sqlite3pager_close(pBt->pPager);
sqliteFree(pBt);
sqliteFree(p);
*ppBtree = 0;
return rc;
}
p->pBt = pBt;
sqlite3pager_set_destructor(pBt->pPager, pageDestructor);
sqlite3pager_set_reiniter(pBt->pPager, pageReinit);
pBt->pCursor = 0;
pBt->pPage1 = 0;
pBt->readOnly = sqlite3pager_isreadonly(pBt->pPager);
sqlite3pager_read_fileheader(pBt->pPager, sizeof(zDbHeader), zDbHeader);
pBt->pageSize = get2byte(&zDbHeader[16]);
if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
|| ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
pBt->pageSize = SQLITE_DEFAULT_PAGE_SIZE;
pBt->maxEmbedFrac = 64; /* 25% */
pBt->minEmbedFrac = 32; /* 12.5% */
pBt->minLeafFrac = 32; /* 12.5% */
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the magic name ":memory:" will create an in-memory database, then
** do not set the auto-vacuum flag, 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. Respect the auto-vacuum
** default in this case.
*/
if( zFilename && !isMemdb ){
pBt->autoVacuum = SQLITE_DEFAULT_AUTOVACUUM;
}
#endif
nReserve = 0;
}else{
nReserve = zDbHeader[20];
pBt->maxEmbedFrac = zDbHeader[21];
pBt->minEmbedFrac = zDbHeader[22];
pBt->minLeafFrac = zDbHeader[23];
pBt->pageSizeFixed = 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
#endif
}
pBt->usableSize = pBt->pageSize - nReserve;
assert( (pBt->pageSize & 7)==0 ); /* 8-byte alignment of pageSize */
sqlite3pager_set_pagesize(pBt->pPager, pBt->pageSize);
#ifndef SQLITE_OMIT_SHARED_CACHE
/* Add the new btree to the linked list starting at ThreadData.pBtree */
if( pTsd->useSharedData && zFilename && !isMemdb ){
pBt->pNext = pTsd->pBtree;
pTsd->pBtree = pBt;
}
#endif
pBt->nRef = 1;
*ppBtree = p;
return SQLITE_OK;
}
/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *p){
BtShared *pBt = p->pBt;
BtCursor *pCur;
#ifndef SQLITE_OMIT_SHARED_CACHE
ThreadData *pTsd = sqlite3ThreadData();
#endif
/* Drop any table-locks */
unlockAllTables(p);
/* Close all cursors opened via this handle. */
pCur = pBt->pCursor;
while( pCur ){
BtCursor *pTmp = pCur;
pCur = pCur->pNext;
if( pTmp->pBtree==p ){
sqlite3BtreeCloseCursor(pTmp);
}
}
sqliteFree(p);
#ifndef SQLITE_OMIT_SHARED_CACHE
/* 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( pBt->nRef>0 );
pBt->nRef--;
if( pBt->nRef ){
return SQLITE_OK;
}
/* Remove the shared-btree from the thread wide list */
if( pTsd->pBtree==pBt ){
pTsd->pBtree = pBt->pNext;
}else{
BtShared *pPrev;
for(pPrev=pTsd->pBtree; pPrev && pPrev->pNext!=pBt; pPrev=pPrev->pNext);
if( pPrev ){
pPrev->pNext = pBt->pNext;
}
}
#endif
/* Close the pager and free the shared-btree structure */
assert( !pBt->pCursor );
sqlite3pager_close(pBt->pPager);
if( pBt->xFreeSchema && pBt->pSchema ){
pBt->xFreeSchema(pBt->pSchema);
}
sqliteFree(pBt->pSchema);
sqliteFree(pBt);
return SQLITE_OK;
}
/*
** Change the busy handler callback function.
*/
int sqlite3BtreeSetBusyHandler(Btree *p, BusyHandler *pHandler){
BtShared *pBt = p->pBt;
pBt->pBusyHandler = pHandler;
sqlite3pager_set_busyhandler(pBt->pPager, pHandler);
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;
sqlite3pager_set_cachesize(pBt->pPager, mxPage);
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){
BtShared *pBt = p->pBt;
sqlite3pager_set_safety_level(pBt->pPager, level);
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;
assert( pBt && pBt->pPager );
return sqlite3pager_nosync(pBt->pPager);
}
#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){
BtShared *pBt = p->pBt;
if( pBt->pageSizeFixed ){
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 = sqlite3pager_set_pagesize(pBt->pPager, pageSize);
}
pBt->usableSize = pBt->pageSize - nReserve;
return SQLITE_OK;
}
/*
** Return the currently defined page size
*/
int sqlite3BtreeGetPageSize(Btree *p){
return p->pBt->pageSize;
}
int sqlite3BtreeGetReserve(Btree *p){
return p->pBt->pageSize - p->pBt->usableSize;
}
#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){
BtShared *pBt = p->pBt;;
#ifdef SQLITE_OMIT_AUTOVACUUM
return SQLITE_READONLY;
#else
if( pBt->pageSizeFixed ){
return SQLITE_READONLY;
}
pBt->autoVacuum = (autoVacuum?1:0);
return SQLITE_OK;
#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 0;
#else
return p->pBt->autoVacuum;
#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. SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(BtShared *pBt){
int rc, pageSize;
MemPage *pPage1;
if( pBt->pPage1 ) return SQLITE_OK;
rc = getPage(pBt, 1, &pPage1);
if( rc!=SQLITE_OK ) return rc;
/* Do some checking to help insure the file we opened really is
** a valid database file.
*/
rc = SQLITE_NOTADB;
if( sqlite3pager_pagecount(pBt->pPager)>0 ){
u8 *page1 = pPage1->aData;
if( memcmp(page1, zMagicHeader, 16)!=0 ){
goto page1_init_failed;
}
if( page1[18]>1 || page1[19]>1 ){
goto page1_init_failed;
}
pageSize = get2byte(&page1[16]);
if( ((pageSize-1)&pageSize)!=0 ){
goto page1_init_failed;
}
assert( (pageSize & 7)==0 );
pBt->pageSize = pageSize;
pBt->usableSize = pageSize - page1[20];
if( pBt->usableSize<500 ){
goto page1_init_failed;
}
pBt->maxEmbedFrac = page1[21];
pBt->minEmbedFrac = page1[22];
pBt->minLeafFrac = page1[23];
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&page1[36 + 4*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)*pBt->maxEmbedFrac/255 - 23;
pBt->minLocal = (pBt->usableSize-12)*pBt->minEmbedFrac/255 - 23;
pBt->maxLeaf = pBt->usableSize - 35;
pBt->minLeaf = (pBt->usableSize-12)*pBt->minLeafFrac/255 - 23;
if( pBt->minLocal>pBt->maxLocal || pBt->maxLocal<0 ){
goto page1_init_failed;
}
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;
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){
if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
if( pBt->pPage1->aData==0 ){
MemPage *pPage = pBt->pPage1;
pPage->aData = &((u8*)pPage)[-pBt->pageSize];
pPage->pBt = pBt;
pPage->pgno = 1;
}
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;
if( sqlite3pager_pagecount(pBt->pPager)>0 ) return SQLITE_OK;
pP1 = pBt->pPage1;
assert( pP1!=0 );
data = pP1->aData;
rc = sqlite3pager_write(data);
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] = pBt->maxEmbedFrac;
data[22] = pBt->minEmbedFrac;
data[23] = pBt->minLeafFrac;
memset(&data[24], 0, 100-24);
zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
pBt->pageSizeFixed = 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
put4byte(&data[36 + 4*4], 1);
}
#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;
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) ){
return SQLITE_OK;
}
/* Write transactions are not possible on a read-only database */
if( pBt->readOnly && wrflag ){
return SQLITE_READONLY;
}
/* 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 ){
return SQLITE_BUSY;
}
do {
if( pBt->pPage1==0 ){
rc = lockBtree(pBt);
}
if( rc==SQLITE_OK && wrflag ){
rc = sqlite3pager_begin(pBt->pPage1->aData, 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 &&
sqlite3InvokeBusyHandler(pBt->pBusyHandler) );
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;
}
}
btreeIntegrity(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 = SQLITE_OK; /* Return code */
BtShared *pBt = pPage->pBt;
int isInitOrig = pPage->isInit;
Pgno pgno = pPage->pgno;
initPage(pPage, 0);
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){
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;
initPage(pPage, 0);
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
if( eType==PTRMAP_OVERFLOW1 ){
CellInfo info;
parseCellPtr(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 */
){
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 );
/* Move page iDbPage from it's 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 = sqlite3pager_movepage(pPager, pDbPage->aData, iFreePage);
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 = getPage(pBt, iPtrPage, &pPtrPage);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3pager_write(pPtrPage->aData);
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 autoVacuumCommit(). */
static int allocatePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
/*
** This routine is called prior to sqlite3pager_commit when a transaction
** is commited for an auto-vacuum database.
*/
static int autoVacuumCommit(BtShared *pBt, Pgno *nTrunc){
Pager *pPager = pBt->pPager;
Pgno nFreeList; /* Number of pages remaining on the free-list. */
int nPtrMap; /* Number of pointer-map pages deallocated */
Pgno origSize; /* Pages in the database file */
Pgno finSize; /* Pages in the database file after truncation */
int rc; /* Return code */
u8 eType;
int pgsz = pBt->pageSize; /* Page size for this database */
Pgno iDbPage; /* The database page to move */
MemPage *pDbMemPage = 0; /* "" */
Pgno iPtrPage; /* The page that contains a pointer to iDbPage */
Pgno iFreePage; /* The free-list page to move iDbPage to */
MemPage *pFreeMemPage = 0; /* "" */
#ifndef NDEBUG
int nRef = *sqlite3pager_stats(pPager);
#endif
assert( pBt->autoVacuum );
if( PTRMAP_ISPAGE(pgsz, sqlite3pager_pagecount(pPager)) ){
return SQLITE_CORRUPT_BKPT;
}
/* Figure out how many free-pages are in the database. If there are no
** free pages, then auto-vacuum is a no-op.
*/
nFreeList = get4byte(&pBt->pPage1->aData[36]);
if( nFreeList==0 ){
*nTrunc = 0;
return SQLITE_OK;
}
origSize = sqlite3pager_pagecount(pPager);
nPtrMap = (nFreeList-origSize+PTRMAP_PAGENO(pgsz, origSize)+pgsz/5)/(pgsz/5);
finSize = origSize - nFreeList - nPtrMap;
if( origSize>=PENDING_BYTE_PAGE(pBt) && finSize<=PENDING_BYTE_PAGE(pBt) ){
finSize--;
if( PTRMAP_ISPAGE(pBt->usableSize, finSize) ){
finSize--;
}
}
TRACE(("AUTOVACUUM: Begin (db size %d->%d)\n", origSize, finSize));
/* Variable 'finSize' will be the size of the file in pages after
** the auto-vacuum has completed (the current file size minus the number
** of pages on the free list). Loop through the pages that lie beyond
** this mark, and if they are not already on the free list, move them
** to a free page earlier in the file (somewhere before finSize).
*/
for( iDbPage=finSize+1; iDbPage<=origSize; iDbPage++ ){
/* If iDbPage is a pointer map page, or the pending-byte page, skip it. */
if( PTRMAP_ISPAGE(pgsz, iDbPage) || iDbPage==PENDING_BYTE_PAGE(pBt) ){
continue;
}
rc = ptrmapGet(pBt, iDbPage, &eType, &iPtrPage);
if( rc!=SQLITE_OK ) goto autovacuum_out;
if( eType==PTRMAP_ROOTPAGE ){
rc = SQLITE_CORRUPT_BKPT;
goto autovacuum_out;
}
/* If iDbPage is free, do not swap it. */
if( eType==PTRMAP_FREEPAGE ){
continue;
}
rc = getPage(pBt, iDbPage, &pDbMemPage);
if( rc!=SQLITE_OK ) goto autovacuum_out;
/* Find the next page in the free-list that is not already at the end
** of the file. A page can be pulled off the free list using the
** allocatePage() routine.
*/
do{
if( pFreeMemPage ){
releasePage(pFreeMemPage);
pFreeMemPage = 0;
}
rc = allocatePage(pBt, &pFreeMemPage, &iFreePage, 0, 0);
if( rc!=SQLITE_OK ){
releasePage(pDbMemPage);
goto autovacuum_out;
}
assert( iFreePage<=origSize );
}while( iFreePage>finSize );
releasePage(pFreeMemPage);
pFreeMemPage = 0;
/* Relocate the page into the body of the file. Note that although the
** page has moved within the database file, the pDbMemPage pointer
** remains valid. This means that this function can run without
** invalidating cursors open on the btree. This is important in
** shared-cache mode.
*/
rc = relocatePage(pBt, pDbMemPage, eType, iPtrPage, iFreePage);
releasePage(pDbMemPage);
if( rc!=SQLITE_OK ) goto autovacuum_out;
}
/* The entire free-list has been swapped to the end of the file. So
** truncate the database file to finSize pages and consider the
** free-list empty.
*/
rc = sqlite3pager_write(pBt->pPage1->aData);
if( rc!=SQLITE_OK ) goto autovacuum_out;
put4byte(&pBt->pPage1->aData[32], 0);
put4byte(&pBt->pPage1->aData[36], 0);
if( rc!=SQLITE_OK ) goto autovacuum_out;
*nTrunc = finSize;
autovacuum_out:
assert( nRef==*sqlite3pager_stats(pPager) );
if( rc!=SQLITE_OK ){
sqlite3pager_rollback(pPager);
}
return rc;
}
#endif
/*
** Commit the transaction currently in progress.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommit(Btree *p){
int rc = SQLITE_OK;
BtShared *pBt = p->pBt;
btreeIntegrity(p);
unlockAllTables(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 ){
assert( pBt->inTransaction==TRANS_WRITE );
assert( pBt->nTransaction>0 );
rc = sqlite3pager_commit(pBt->pPager);
pBt->inTransaction = TRANS_READ;
pBt->inStmt = 0;
}
/* 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);
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.
*/
static int countWriteCursors(BtShared *pBt){
BtCursor *pCur;
int r = 0;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->wrFlag ) r++;
}
return r;
}
#endif
#ifdef SQLITE_TEST
/*
** Print debugging information about all cursors to standard output.
*/
void sqlite3BtreeCursorList(Btree *p){
BtCursor *pCur;
BtShared *pBt = p->pBt;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
MemPage *pPage = pCur->pPage;
char *zMode = pCur->wrFlag ? "rw" : "ro";
sqlite3DebugPrintf("CURSOR %p rooted at %4d(%s) currently at %d.%d%s\n",
pCur, pCur->pgnoRoot, zMode,
pPage ? pPage->pgno : 0, pCur->idx,
(pCur->eState==CURSOR_VALID) ? "" : " eof"
);
}
}
#endif
/*
** 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 = SQLITE_OK;
BtShared *pBt = p->pBt;
MemPage *pPage1;
btreeIntegrity(p);
unlockAllTables(p);
if( p->inTrans==TRANS_WRITE ){
assert( TRANS_WRITE==pBt->inTransaction );
rc = sqlite3pager_rollback(pBt->pPager);
/* The rollback may have destroyed the pPage1->aData value. So
** call getPage() on page 1 again to make sure pPage1->aData is
** set correctly. */
if( getPage(pBt, 1, &pPage1)==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);
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;
if( (p->inTrans!=TRANS_WRITE) || pBt->inStmt ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( pBt->inTransaction==TRANS_WRITE );
rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_stmt_begin(pBt->pPager);
pBt->inStmt = 1;
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;
if( pBt->inStmt && !pBt->readOnly ){
rc = sqlite3pager_stmt_commit(pBt->pPager);
}else{
rc = SQLITE_OK;
}
pBt->inStmt = 0;
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;
BtShared *pBt = p->pBt;
if( pBt->inStmt==0 || pBt->readOnly ) return SQLITE_OK;
rc = sqlite3pager_stmt_rollback(pBt->pPager);
assert( countWriteCursors(pBt)==0 );
pBt->inStmt = 0;
return rc;
}
/*
** Default key comparison function to be used if no comparison function
** is specified on the sqlite3BtreeCursor() call.
*/
static int dfltCompare(
void *NotUsed, /* User data is not used */
int n1, const void *p1, /* First key to compare */
int n2, const void *p2 /* Second key to compare */
){
int c;
c = memcmp(p1, p2, n1<n2 ? n1 : n2);
if( c==0 ){
c = n1 - n2;
}
return c;
}
/*
** 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: No other cursors may be open with wrFlag==0 on the same table
**
** 3: The database must be writable (not on read-only media)
**
** 4: There must be an active transaction.
**
** Condition 2 warrants further discussion. If any cursor is opened
** on a table with wrFlag==0, that prevents all other cursors from
** writing to that table. This is a kind of "read-lock". When a cursor
** is opened with wrFlag==0 it is guaranteed that the table will not
** change as long as the cursor is open. This allows the cursor to
** do a sequential scan of the table without having to worry about
** entries being inserted or deleted during the scan. Cursors should
** be opened with wrFlag==0 only if this read-lock property is needed.
** That is to say, cursors should be opened with wrFlag==0 only if they
** intend to use the sqlite3BtreeNext() system call. All other cursors
** should be opened with wrFlag==1 even if they never really intend
** to write.
**
** 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.
**
** The comparison function must be logically the same for every cursor
** on a particular table. Changing the comparison function will result
** in incorrect operations. If the comparison function is NULL, a
** default comparison function is used. The comparison function is
** always ignored for INTKEY tables.
*/
int sqlite3BtreeCursor(
Btree *p, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
int (*xCmp)(void*,int,const void*,int,const void*), /* Key Comparison func */
void *pArg, /* First arg to xCompare() */
BtCursor **ppCur /* Write new cursor here */
){
int rc;
BtCursor *pCur;
BtShared *pBt = p->pBt;
*ppCur = 0;
if( wrFlag ){
if( pBt->readOnly ){
return SQLITE_READONLY;
}
if( checkReadLocks(pBt, iTable, 0) ){
return SQLITE_LOCKED;
}
}
if( pBt->pPage1==0 ){
rc = lockBtreeWithRetry(p);
if( rc!=SQLITE_OK ){
return rc;
}
}
pCur = sqliteMalloc( sizeof(*pCur) );
if( pCur==0 ){
rc = SQLITE_NOMEM;
goto create_cursor_exception;
}
pCur->pgnoRoot = (Pgno)iTable;
pCur->pPage = 0; /* For exit-handler, in case getAndInitPage() fails. */
if( iTable==1 && sqlite3pager_pagecount(pBt->pPager)==0 ){
rc = SQLITE_EMPTY;
goto create_cursor_exception;
}
rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->pPage, 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->xCompare = xCmp ? xCmp : dfltCompare;
pCur->pArg = pArg;
pCur->pBtree = p;
pCur->wrFlag = wrFlag;
pCur->idx = 0;
memset(&pCur->info, 0, sizeof(pCur->info));
pCur->pNext = pBt->pCursor;
if( pCur->pNext ){
pCur->pNext->pPrev = pCur;
}
pCur->pPrev = 0;
pBt->pCursor = pCur;
pCur->eState = CURSOR_INVALID;
*ppCur = pCur;
return SQLITE_OK;
create_cursor_exception:
if( pCur ){
releasePage(pCur->pPage);
sqliteFree(pCur);
}
unlockBtreeIfUnused(pBt);
return rc;
}
#if 0 /* Not Used */
/*
** Change the value of the comparison function used by a cursor.
*/
void sqlite3BtreeSetCompare(
BtCursor *pCur, /* The cursor to whose comparison function is changed */
int(*xCmp)(void*,int,const void*,int,const void*), /* New comparison func */
void *pArg /* First argument to xCmp() */
){
pCur->xCompare = xCmp ? xCmp : dfltCompare;
pCur->pArg = pArg;
}
#endif
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
BtShared *pBt = pCur->pBtree->pBt;
restoreCursorPosition(pCur, 0);
if( pCur->pPrev ){
pCur->pPrev->pNext = pCur->pNext;
}else{
pBt->pCursor = pCur->pNext;
}
if( pCur->pNext ){
pCur->pNext->pPrev = pCur->pPrev;
}
releasePage(pCur->pPage);
unlockBtreeIfUnused(pBt);
sqliteFree(pCur);
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.
*/
static void getTempCursor(BtCursor *pCur, BtCursor *pTempCur){
memcpy(pTempCur, pCur, sizeof(*pCur));
pTempCur->pNext = 0;
pTempCur->pPrev = 0;
if( pTempCur->pPage ){
sqlite3pager_ref(pTempCur->pPage->aData);
}
}
/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
static void releaseTempCursor(BtCursor *pCur){
if( pCur->pPage ){
sqlite3pager_unref(pCur->pPage->aData);
}
}
/*
** Make sure the BtCursor.info field of the given cursor is valid.
** If it is not already valid, call parseCell() 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 parseCell().
*/
static void getCellInfo(BtCursor *pCur){
if( pCur->info.nSize==0 ){
parseCell(pCur->pPage, pCur->idx, &pCur->info);
}else{
#ifndef NDEBUG
CellInfo info;
memset(&info, 0, sizeof(info));
parseCell(pCur->pPage, pCur->idx, &info);
assert( memcmp(&info, &pCur->info, sizeof(info))==0 );
#endif
}
}
/*
** 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 = restoreCursorPosition(pCur, 1);
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 = restoreCursorPosition(pCur, 1);
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;
}
/*
** Read payload information from the entry that the pCur cursor is
** pointing to. Begin reading the payload at "offset" and read
** a total of "amt" bytes. Put the result in zBuf.
**
** This routine does not make a distinction between key and data.
** It just reads bytes from the payload area. Data might appear
** on the main page or be scattered out on multiple overflow pages.
*/
static int getPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
int offset, /* Begin reading this far into payload */
int amt, /* Read this many bytes */
unsigned char *pBuf, /* Write the bytes into this buffer */
int skipKey /* offset begins at data if this is true */
){
unsigned char *aPayload;
Pgno nextPage;
int rc;
MemPage *pPage;
BtShared *pBt;
int ovflSize;
u32 nKey;
assert( pCur!=0 && pCur->pPage!=0 );
assert( pCur->eState==CURSOR_VALID );
pBt = pCur->pBtree->pBt;
pPage = pCur->pPage;
pageIntegrity(pPage);
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
getCellInfo(pCur);
aPayload = pCur->info.pCell;
aPayload += pCur->info.nHeader;
if( pPage->intKey ){
nKey = 0;
}else{
nKey = pCur->info.nKey;
}
assert( offset>=0 );
if( skipKey ){
offset += nKey;
}
if( offset+amt > nKey+pCur->info.nData ){
return SQLITE_ERROR;
}
if( offset<pCur->info.nLocal ){
int a = amt;
if( a+offset>pCur->info.nLocal ){
a = pCur->info.nLocal - offset;
}
memcpy(pBuf, &aPayload[offset], a);
if( a==amt ){
return SQLITE_OK;
}
offset = 0;
pBuf += a;
amt -= a;
}else{
offset -= pCur->info.nLocal;
}
ovflSize = pBt->usableSize - 4;
if( amt>0 ){
nextPage = get4byte(&aPayload[pCur->info.nLocal]);
while( amt>0 && nextPage ){
rc = sqlite3pager_get(pBt->pPager, nextPage, (void**)&aPayload);
if( rc!=0 ){
return rc;
}
nextPage = get4byte(aPayload);
if( offset<ovflSize ){
int a = amt;
if( a + offset > ovflSize ){
a = ovflSize - offset;
}
memcpy(pBuf, &aPayload[offset+4], a);
offset = 0;
amt -= a;
pBuf += a;
}else{
offset -= ovflSize;
}
sqlite3pager_unref(aPayload);
}
}
if( amt>0 ){
return SQLITE_CORRUPT_BKPT;
}
return SQLITE_OK;
}
/*
** 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 = restoreCursorPosition(pCur, 1);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
assert( pCur->pPage!=0 );
if( pCur->pPage->intKey ){
return SQLITE_CORRUPT_BKPT;
}
assert( pCur->pPage->intKey==0 );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
rc = getPayload(pCur, offset, amt, (unsigned char*)pBuf, 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 = restoreCursorPosition(pCur, 1);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
assert( pCur->pPage!=0 );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
rc = getPayload(pCur, offset, amt, pBuf, 1);
}
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 getPayload() 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;
int nLocal;
assert( pCur!=0 && pCur->pPage!=0 );
assert( pCur->eState==CURSOR_VALID );
pPage = pCur->pPage;
pageIntegrity(pPage);
assert( pCur->idx>=0 && pCur->idx<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.
**
** 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){
if( pCur->eState==CURSOR_VALID ){
return (const void*)fetchPayload(pCur, pAmt, 0);
}
return 0;
}
const void *sqlite3BtreeDataFetch(BtCursor *pCur, int *pAmt){
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;
MemPage *pNewPage;
MemPage *pOldPage;
BtShared *pBt = pCur->pBtree->pBt;
assert( pCur->eState==CURSOR_VALID );
rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
if( rc ) return rc;
pageIntegrity(pNewPage);
pNewPage->idxParent = pCur->idx;
pOldPage = pCur->pPage;
pOldPage->idxShift = 0;
releasePage(pOldPage);
pCur->pPage = pNewPage;
pCur->idx = 0;
pCur->info.nSize = 0;
if( pNewPage->nCell<1 ){
return SQLITE_CORRUPT_BKPT;
}
return SQLITE_OK;
}
/*
** Return true if the page is the virtual root of its table.
**
** The virtual root page is the root page for most tables. But
** for the table rooted on page 1, sometime the real root page
** is empty except for the right-pointer. In such cases the
** virtual root page is the page that the right-pointer of page
** 1 is pointing to.
*/
static int isRootPage(MemPage *pPage){
MemPage *pParent = pPage->pParent;
if( pParent==0 ) return 1;
if( pParent->pgno>1 ) return 0;
if( get2byte(&pParent->aData[pParent->hdrOffset+3])==0 ) return 1;
return 0;
}
/*
** 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.
*/
static void moveToParent(BtCursor *pCur){
MemPage *pParent;
MemPage *pPage;
int idxParent;
assert( pCur->eState==CURSOR_VALID );
pPage = pCur->pPage;
assert( pPage!=0 );
assert( !isRootPage(pPage) );
pageIntegrity(pPage);
pParent = pPage->pParent;
assert( pParent!=0 );
pageIntegrity(pParent);
idxParent = pPage->idxParent;
sqlite3pager_ref(pParent->aData);
releasePage(pPage);
pCur->pPage = pParent;
pCur->info.nSize = 0;
assert( pParent->idxShift==0 );
pCur->idx = idxParent;
}
/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
MemPage *pRoot;
int rc;
BtShared *pBt = pCur->pBtree->pBt;
if(
SQLITE_OK!=(rc = restoreCursorPosition(pCur, 0)) ||
SQLITE_OK!=(rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0))
){
pCur->eState = CURSOR_INVALID;
return rc;
}
releasePage(pCur->pPage);
pageIntegrity(pRoot);
pCur->pPage = pRoot;
pCur->idx = 0;
pCur->info.nSize = 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);
}
pCur->eState = ((pCur->pPage->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.
*/
static int moveToLeftmost(BtCursor *pCur){
Pgno pgno;
int rc;
MemPage *pPage;
assert( pCur->eState==CURSOR_VALID );
while( !(pPage = pCur->pPage)->leaf ){
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
pgno = get4byte(findCell(pPage, pCur->idx));
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
return SQLITE_OK;
}
/*
** 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*.
*/
static int moveToRightmost(BtCursor *pCur){
Pgno pgno;
int rc;
MemPage *pPage;
assert( pCur->eState==CURSOR_VALID );
while( !(pPage = pCur->pPage)->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
pCur->idx = pPage->nCell;
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
pCur->idx = pPage->nCell - 1;
pCur->info.nSize = 0;
return SQLITE_OK;
}
/* 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;
rc = moveToRoot(pCur);
if( rc ) return rc;
if( pCur->eState==CURSOR_INVALID ){
assert( pCur->pPage->nCell==0 );
*pRes = 1;
return SQLITE_OK;
}
assert( pCur->pPage->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;
rc = moveToRoot(pCur);
if( rc ) return rc;
if( CURSOR_INVALID==pCur->eState ){
assert( pCur->pPage->nCell==0 );
*pRes = 1;
return SQLITE_OK;
}
assert( pCur->eState==CURSOR_VALID );
*pRes = 0;
rc = moveToRightmost(pCur);
return rc;
}
/* Move the cursor so that it points to an entry near pKey/nKey.
** Return a success code.
**
** For INTKEY tables, only the nKey parameter is used. pKey is
** ignored. For other tables, nKey is the number of bytes of data
** in pKey. The comparison function specified when the cursor was
** created is used to compare keys.
**
** 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 sqlite3BtreeMoveto(BtCursor *pCur, const void *pKey, i64 nKey, int *pRes){
int rc;
rc = moveToRoot(pCur);
if( rc ) return rc;
assert( pCur->pPage );
assert( pCur->pPage->isInit );
if( pCur->eState==CURSOR_INVALID ){
*pRes = -1;
assert( pCur->pPage->nCell==0 );
return SQLITE_OK;
}
for(;;){
int lwr, upr;
Pgno chldPg;
MemPage *pPage = pCur->pPage;
int c = -1; /* pRes return if table is empty must be -1 */
lwr = 0;
upr = pPage->nCell-1;
if( !pPage->intKey && pKey==0 ){
return SQLITE_CORRUPT_BKPT;
}
pageIntegrity(pPage);
while( lwr<=upr ){
void *pCellKey;
i64 nCellKey;
pCur->idx = (lwr+upr)/2;
pCur->info.nSize = 0;
sqlite3BtreeKeySize(pCur, &nCellKey);
if( pPage->intKey ){
if( nCellKey<nKey ){
c = -1;
}else if( nCellKey>nKey ){
c = +1;
}else{
c = 0;
}
}else{
int available;
pCellKey = (void *)fetchPayload(pCur, &available, 0);
if( available>=nCellKey ){
c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
}else{
pCellKey = sqliteMallocRaw( nCellKey );
if( pCellKey==0 ) return SQLITE_NOMEM;
rc = sqlite3BtreeKey(pCur, 0, nCellKey, (void *)pCellKey);
c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
sqliteFree(pCellKey);
if( rc ) return rc;
}
}
if( c==0 ){
if( pPage->leafData && !pPage->leaf ){
lwr = pCur->idx;
upr = lwr - 1;
break;
}else{
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
}
if( c<0 ){
lwr = pCur->idx+1;
}else{
upr = pCur->idx-1;
}
}
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->idx>=0 && pCur->idx<pCur->pPage->nCell );
if( pRes ) *pRes = c;
return SQLITE_OK;
}
pCur->idx = lwr;
pCur->info.nSize = 0;
rc = moveToChild(pCur, chldPg);
if( rc ){
return rc;
}
}
/* NOT REACHED */
}
/*
** 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);
}
/*
** 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;
MemPage *pPage = pCur->pPage;
#ifndef SQLITE_OMIT_SHARED_CACHE
rc = restoreCursorPosition(pCur, 1);
if( rc!=SQLITE_OK ){
return rc;
}
if( pCur->skip>0 ){
pCur->skip = 0;
*pRes = 0;
return SQLITE_OK;
}
pCur->skip = 0;
#endif
assert( pRes!=0 );
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
assert( pPage->isInit );
assert( pCur->idx<pPage->nCell );
pCur->idx++;
pCur->info.nSize = 0;
if( pCur->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( isRootPage(pPage) ){
*pRes = 1;
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
}
moveToParent(pCur);
pPage = pCur->pPage;
}while( pCur->idx>=pPage->nCell );
*pRes = 0;
if( pPage->leafData ){
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;
Pgno pgno;
MemPage *pPage;
#ifndef SQLITE_OMIT_SHARED_CACHE
rc = restoreCursorPosition(pCur, 1);
if( rc!=SQLITE_OK ){
return rc;
}
if( pCur->skip<0 ){
pCur->skip = 0;
*pRes = 0;
return SQLITE_OK;
}
pCur->skip = 0;
#endif
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
pPage = pCur->pPage;
assert( pPage->isInit );
assert( pCur->idx>=0 );
if( !pPage->leaf ){
pgno = get4byte( findCell(pPage, pCur->idx) );
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
rc = moveToRightmost(pCur);
}else{
while( pCur->idx==0 ){
if( isRootPage(pPage) ){
pCur->eState = CURSOR_INVALID;
*pRes = 1;
return SQLITE_OK;
}
moveToParent(pCur);
pPage = pCur->pPage;
}
pCur->idx--;
pCur->info.nSize = 0;
if( pPage->leafData && !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, sqlite3pager_write()
** has already been called on the new page.) The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite3pager_unref() 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 sqlite3pager_unref() 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 allocatePage(
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 */
pPage1 = pBt->pPage1;
n = get4byte(&pPage1->aData[36]);
if( n>0 ){
/* There are pages on the freelist. Reuse one of those pages. */
MemPage *pTrunk = 0;
Pgno iTrunk;
MemPage *pPrevTrunk = 0;
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 ){
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 = sqlite3pager_write(pPage1->aData);
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 = getPage(pBt, iTrunk, &pTrunk);
if( rc ){
releasePage(pPrevTrunk);
return rc;
}
/* TODO: This should move to after the loop? */
rc = sqlite3pager_write(pTrunk->aData);
if( rc ){
releasePage(pTrunk);
releasePage(pPrevTrunk);
return rc;
}
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 );
*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 - 8 ){
/* Value of k is out of range. Database corruption */
return SQLITE_CORRUPT_BKPT;
#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;
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 = getPage(pBt, iNewTrunk, &pNewTrunk);
if( rc!=SQLITE_OK ){
releasePage(pTrunk);
releasePage(pPrevTrunk);
return rc;
}
rc = sqlite3pager_write(pNewTrunk->aData);
if( rc!=SQLITE_OK ){
releasePage(pNewTrunk);
releasePage(pTrunk);
releasePage(pPrevTrunk);
return rc;
}
memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
put4byte(&pNewTrunk->aData[4], k-1);
memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
if( !pPrevTrunk ){
put4byte(&pPage1->aData[32], iNewTrunk);
}else{
put4byte(&pPrevTrunk->aData[0], iNewTrunk);
}
releasePage(pNewTrunk);
}
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;
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 ){
*pPgno = iPage;
if( *pPgno>sqlite3pager_pagecount(pBt->pPager) ){
/* Free page off the end of the file */
return SQLITE_CORRUPT_BKPT;
}
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);
rc = getPage(pBt, *pPgno, ppPage);
if( rc==SQLITE_OK ){
sqlite3pager_dont_rollback((*ppPage)->aData);
rc = sqlite3pager_write((*ppPage)->aData);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
}
}
searchList = 0;
}
}
releasePage(pPrevTrunk);
}while( searchList );
releasePage(pTrunk);
}else{
/* There are no pages on the freelist, so create a new page at the
** end of the file */
*pPgno = sqlite3pager_pagecount(pBt->pPager) + 1;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt->usableSize, *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)++;
}
#endif
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
rc = getPage(pBt, *pPgno, ppPage);
if( rc ) return rc;
rc = sqlite3pager_write((*ppPage)->aData);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
}
TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
}
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
return rc;
}
/*
** Add a page of the database file to the freelist.
**
** sqlite3pager_unref() 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( pPage->pgno>1 );
pPage->isInit = 0;
releasePage(pPage->pParent);
pPage->pParent = 0;
/* Increment the free page count on pPage1 */
rc = sqlite3pager_write(pPage1->aData);
if( rc ) return rc;
n = get4byte(&pPage1->aData[36]);
put4byte(&pPage1->aData[36], n+1);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the database supports auto-vacuum, write an entry in the pointer-map
** to indicate that the page is free.
*/
if( pBt->autoVacuum ){
rc = ptrmapPut(pBt, pPage->pgno, PTRMAP_FREEPAGE, 0);
if( rc ) return rc;
}
#endif
if( n==0 ){
/* This is the first free page */
rc = sqlite3pager_write(pPage->aData);
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 = getPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk);
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. */
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
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{
/* Add the newly freed page as a leaf on the current trunk */
rc = sqlite3pager_write(pTrunk->aData);
if( rc ) return rc;
put4byte(&pTrunk->aData[4], k+1);
put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
sqlite3pager_dont_write(pBt->pPager, pPage->pgno);
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;
parseCellPtr(pPage, pCell, &info);
if( info.iOverflow==0 ){
return SQLITE_OK; /* No overflow pages. Return without doing anything */
}
ovflPgno = get4byte(&pCell[info.iOverflow]);
while( ovflPgno!=0 ){
MemPage *pOvfl;
if( ovflPgno>sqlite3pager_pagecount(pBt->pPager) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getPage(pBt, ovflPgno, &pOvfl);
if( rc ) return rc;
ovflPgno = get4byte(pOvfl->aData);
rc = freePage(pOvfl);
sqlite3pager_unref(pOvfl->aData);
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 *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;
/* Fill in the header. */
nHeader = 0;
if( !pPage->leaf ){
nHeader += 4;
}
if( pPage->hasData ){
nHeader += putVarint(&pCell[nHeader], nData);
}else{
nData = 0;
}
nHeader += putVarint(&pCell[nHeader], *(u64*)&nKey);
parseCellPtr(pPage, pCell, &info);
assert( info.nHeader==nHeader );
assert( info.nKey==nKey );
assert( info.nData==nData );
/* Fill in the payload */
nPayload = nData;
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 ){
#ifndef SQLITE_OMIT_AUTOVACUUM
Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
#endif
rc = allocatePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, 0);
#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. The entry for the first overflow page will be
** added later, by the insertCell() routine.
*/
if( pBt->autoVacuum && pgnoPtrmap!=0 && rc==SQLITE_OK ){
rc = ptrmapPut(pBt, pgnoOvfl, PTRMAP_OVERFLOW2, pgnoPtrmap);
}
#endif
if( rc ){
releasePage(pToRelease);
/* clearCell(pPage, pCell); */
return rc;
}
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( n>nSrc ) n = nSrc;
memcpy(pPayload, pSrc, n);
nPayload -= n;
pPayload += n;
pSrc += n;
nSrc -= n;
spaceLeft -= n;
if( nSrc==0 ){
nSrc = nData;
pSrc = pData;
}
}
releasePage(pToRelease);
return SQLITE_OK;
}
/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
** pointer in the third argument.
*/
static int reparentPage(BtShared *pBt, Pgno pgno, MemPage *pNewParent, int idx){
MemPage *pThis;
unsigned char *aData;
if( pgno==0 ) return SQLITE_OK;
assert( pBt->pPager!=0 );
aData = sqlite3pager_lookup(pBt->pPager, pgno);
if( aData ){
pThis = (MemPage*)&aData[pBt->pageSize];
assert( pThis->aData==aData );
if( pThis->isInit ){
if( pThis->pParent!=pNewParent ){
if( pThis->pParent ) sqlite3pager_unref(pThis->pParent->aData);
pThis->pParent = pNewParent;
if( pNewParent ) sqlite3pager_ref(pNewParent->aData);
}
pThis->idxParent = idx;
}
sqlite3pager_unref(aData);
}
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
return ptrmapPut(pBt, pgno, PTRMAP_BTREE, pNewParent->pgno);
}
#endif
return SQLITE_OK;
}
/*
** Change the pParent pointer of all children of pPage to point back
** to pPage.
**
** In other words, for every child of pPage, invoke reparentPage()
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static int reparentChildPages(MemPage *pPage){
int i;
BtShared *pBt = pPage->pBt;
int rc = SQLITE_OK;
if( pPage->leaf ) return SQLITE_OK;
for(i=0; i<pPage->nCell; i++){
u8 *pCell = findCell(pPage, i);
if( !pPage->leaf ){
rc = reparentPage(pBt, get4byte(pCell), pPage, i);
if( rc!=SQLITE_OK ) return rc;
}
}
if( !pPage->leaf ){
rc = reparentPage(pBt, get4byte(&pPage->aData[pPage->hdrOffset+8]),
pPage, i);
pPage->idxShift = 0;
}
return rc;
}
/*
** 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 void 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[] */
assert( idx>=0 && idx<pPage->nCell );
assert( sz==cellSize(pPage, idx) );
assert( sqlite3pager_iswriteable(pPage->aData) );
data = pPage->aData;
ptr = &data[pPage->cellOffset + 2*idx];
pc = get2byte(ptr);
assert( pc>10 && pc+sz<=pPage->pBt->usableSize );
freeSpace(pPage, pc, sz);
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;
pPage->idxShift = 1;
}
/*
** 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( sqlite3pager_iswriteable(pPage->aData) );
if( pPage->nOverflow || sz+2>pPage->nFree ){
if( pTemp ){
memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
pCell = pTemp;
}
j = pPage->nOverflow++;
assert( j<sizeof(pPage->aOvfl)/sizeof(pPage->aOvfl[0]) );
pPage->aOvfl[j].pCell = pCell;
pPage->aOvfl[j].idx = i;
pPage->nFree = 0;
}else{
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 ){
int 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]) );
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);
pPage->idxShift = 1;
pageIntegrity(pPage);
#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;
parseCellPtr(pPage, pCell, &info);
if( (info.nData+(pPage->intKey?0:info.nKey))>info.nLocal ){
Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
int 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 */
int *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 );
totalSize = 0;
for(i=0; i<nCell; i++){
totalSize += aSize[i];
}
assert( totalSize+2*nCell<=pPage->nFree );
assert( pPage->nCell==0 );
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(MemPage*, 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(MemPage *pPage, MemPage *pParent){
int rc;
MemPage *pNew;
Pgno pgnoNew;
u8 *pCell;
int szCell;
CellInfo info;
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 */
/* Allocate a new page. Insert the overflow cell from pPage
** into it. Then remove the overflow cell from pPage.
*/
rc = allocatePage(pBt, &pNew, &pgnoNew, 0, 0);
if( rc!=SQLITE_OK ){
return rc;
}
pCell = pPage->aOvfl[0].pCell;
szCell = cellSizePtr(pPage, pCell);
zeroPage(pNew, pPage->aData[0]);
assemblePage(pNew, 1, &pCell, &szCell);
pPage->nOverflow = 0;
/* Set the parent of the newly allocated page to pParent. */
pNew->pParent = pParent;
sqlite3pager_ref(pParent->aData);
/* 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.
*/
assert( pPage->nCell>0 );
parseCellPtr(pPage, findCell(pPage, pPage->nCell-1), &info);
rc = fillInCell(pParent, parentCell, 0, info.nKey, 0, 0, &parentSize);
if( rc!=SQLITE_OK ){
return rc;
}
assert( parentSize<64 );
rc = insertCell(pParent, parentIdx, parentCell, parentSize, 0, 4);
if( rc!=SQLITE_OK ){
return rc;
}
put4byte(findOverflowCell(pParent,parentIdx), pPage->pgno);
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* 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( pBt->autoVacuum ){
rc = ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno);
if( rc!=SQLITE_OK ){
return rc;
}
rc = ptrmapPutOvfl(pNew, 0);
if( rc!=SQLITE_OK ){
return rc;
}
}
#endif
/* Release the reference to the new page and balance the parent page,
** in case the divider cell inserted caused it to become overfull.
*/
releasePage(pNew);
return balance(pParent, 0);
}
#endif /* SQLITE_OMIT_QUICKBALANCE */
/*
** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
** if the database supports auto-vacuum or not. Because it is used
** within an expression that is an argument to another macro
** (sqliteMallocRaw), it is not possible to use conditional compilation.
** So, this macro is defined instead.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
#define ISAUTOVACUUM (pBt->autoVacuum)
#else
#define ISAUTOVACUUM 0
#endif
/*
** 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(MemPage *pPage){
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 iSpace = 0; /* First unused byte of aSpace[] */
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 */
int *szCell; /* Local size of all cells in apCell[] */
u8 *aCopy[NB]; /* Space for holding data of apCopy[] */
u8 *aSpace; /* Space to hold copies of dividers cells */
#ifndef SQLITE_OMIT_AUTOVACUUM
u8 *aFrom = 0;
#endif
/*
** Find the parent page.
*/
assert( pPage->isInit );
assert( sqlite3pager_iswriteable(pPage->aData) );
pBt = pPage->pBt;
pParent = pPage->pParent;
sqlite3pager_write(pParent->aData);
assert( pParent );
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->leafData &&
pPage->nOverflow==1 &&
pPage->aOvfl[0].idx==pPage->nCell &&
pPage->pParent->pgno!=1 &&
get4byte(&pParent->aData[pParent->hdrOffset+8])==pPage->pgno
){
/*
** 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(pPage, pParent);
}
#endif
/*
** 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
*/
if( pParent->idxShift ){
Pgno pgno;
pgno = pPage->pgno;
assert( pgno==sqlite3pager_pagenumber(pPage->aData) );
for(idx=0; idx<pParent->nCell; idx++){
if( get4byte(findCell(pParent, idx))==pgno ){
break;
}
}
assert( idx<pParent->nCell
|| get4byte(&pParent->aData[pParent->hdrOffset+8])==pgno );
}else{
idx = pPage->idxParent;
}
/*
** Initialize variables so that it will be safe to jump
** directly to balance_cleanup at any moment.
*/
nOld = nNew = 0;
sqlite3pager_ref(pParent->aData);
/*
** 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], pParent);
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 2 in order to preserve 8-byte
** alignment */
nMaxCells = (nMaxCells + 1)&~1;
/*
** Allocate space for memory structures
*/
apCell = sqliteMallocRaw(
nMaxCells*sizeof(u8*) /* apCell */
+ nMaxCells*sizeof(int) /* szCell */
+ ROUND8(sizeof(MemPage))*NB /* aCopy */
+ pBt->pageSize*(5+NB) /* aSpace */
+ (ISAUTOVACUUM ? nMaxCells : 0) /* aFrom */
);
if( apCell==0 ){
rc = SQLITE_NOMEM;
goto balance_cleanup;
}
szCell = (int*)&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 */
}
aSpace = &aCopy[NB-1][pBt->pageSize+ROUND8(sizeof(MemPage))];
assert( ((aSpace - (u8*)apCell) & 7)==0 ); /* 8-byte alignment required */
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
aFrom = &aSpace[5*pBt->pageSize];
}
#endif
/*
** 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][pBt->pageSize];
p->aData = &((u8*)p)[-pBt->pageSize];
memcpy(p->aData, apOld[i]->aData, pBt->pageSize + sizeof(MemPage));
/* The memcpy() above changes the value of p->aData so we have to
** set it again. */
p->aData = &((u8*)p)[-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 aSpace[] 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 aSpace[]. 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->leafData && pPage->leaf;
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]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
int a;
aFrom[nCell] = i;
for(a=0; a<pOld->nOverflow; a++){
if( pOld->aOvfl[a].pCell==apCell[nCell] ){
aFrom[nCell] = 0xFF;
break;
}
}
}
#endif
nCell++;
}
if( i<nOld-1 ){
int 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 = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
memcpy(pTemp, apDiv[i], sz);
apCell[nCell] = pTemp+leafCorrection;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
aFrom[nCell] = 0xFF;
}
#endif
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 );
}
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 = sqlite3pager_write(pNew->aData);
if( rc ) goto balance_cleanup;
}else{
rc = allocatePage(pBt, &pNew, &pgnoNew[i], pgnoNew[i-1], 0);
if( rc ) goto balance_cleanup;
apNew[i] = pNew;
}
nNew++;
zeroPage(pNew, pageFlags);
}
/* 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] );
assemblePage(pNew, cntNew[i]-j, &apCell[j], &szCell[j]);
assert( pNew->nCell>0 || (nNew==1 && cntNew[0]==0) );
assert( pNew->nOverflow==0 );
#ifndef SQLITE_OMIT_AUTOVACUUM
/* 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( pBt->autoVacuum ){
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 ){
goto balance_cleanup;
}
}
}
}
#endif
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;
if( !pNew->leaf ){
memcpy(&pNew->aData[8], pCell, 4);
pTemp = 0;
}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--;
parseCellPtr(pNew, apCell[j], &info);
pCell = &aSpace[iSpace];
fillInCell(pParent, pCell, 0, info.nKey, 0, 0, &sz);
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
pTemp = 0;
}else{
pCell -= 4;
pTemp = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
}
rc = insertCell(pParent, nxDiv, pCell, sz, pTemp, 4);
if( rc!=SQLITE_OK ) goto balance_cleanup;
put4byte(findOverflowCell(pParent,nxDiv), pNew->pgno);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* 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( pBt->autoVacuum && !leafData ){
rc = ptrmapPutOvfl(pParent, nxDiv);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
#endif
j++;
nxDiv++;
}
}
assert( j==nCell );
if( (pageFlags & PTF_LEAF)==0 ){
memcpy(&apNew[nNew-1]->aData[8], &apCopy[nOld-1]->aData[8], 4);
}
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]);
}
/*
** Reparent children of all cells.
*/
for(i=0; i<nNew; i++){
rc = reparentChildPages(apNew[i]);
if( rc!=SQLITE_OK ) goto balance_cleanup;
}
rc = reparentChildPages(pParent);
if( rc!=SQLITE_OK ) goto balance_cleanup;
/*
** 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 );
/* assert( pPage->isInit ); // No! pPage might have been added to freelist */
/* pageIntegrity(pPage); // No! pPage might have been added to freelist */
rc = balance(pParent, 0);
/*
** Cleanup before returning.
*/
balance_cleanup:
sqliteFree(apCell);
for(i=0; i<nOld; i++){
releasePage(apOld[i]);
}
for(i=0; i<nNew; i++){
releasePage(apNew[i]);
}
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(MemPage *pPage){
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 */
int *szCell; /* Local size of all cells */
assert( pPage->pParent==0 );
assert( pPage->nCell==0 );
pBt = pPage->pBt;
mxCellPerPage = MX_CELL(pBt);
apCell = sqliteMallocRaw( mxCellPerPage*(sizeof(u8*)+sizeof(int)) );
if( apCell==0 ) return SQLITE_NOMEM;
szCell = (int*)&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.
*/
pgnoChild = get4byte(&pPage->aData[pPage->hdrOffset+8]);
assert( pgnoChild>0 );
assert( pgnoChild<=sqlite3pager_pagecount(pPage->pBt->pPager) );
rc = getPage(pPage->pBt, pgnoChild, &pChild);
if( rc ) goto end_shallow_balance;
if( pPage->pgno==1 ){
rc = initPage(pChild, pPage);
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. */
put4byte(&pPage->aData[pPage->hdrOffset+8],
get4byte(&pChild->aData[pChild->hdrOffset+8]));
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;
pPage->pParent = 0;
rc = initPage(pPage, 0);
assert( rc==SQLITE_OK );
freePage(pChild);
TRACE(("BALANCE: transfer child %d into root %d\n",
pChild->pgno, pPage->pgno));
}
rc = reparentChildPages(pPage);
assert( pPage->nOverflow==0 );
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
int i;
for(i=0; i<pPage->nCell; i++){
rc = ptrmapPutOvfl(pPage, i);
if( rc!=SQLITE_OK ){
goto end_shallow_balance;
}
}
}
#endif
if( rc!=SQLITE_OK ) goto end_shallow_balance;
releasePage(pChild);
}
end_shallow_balance:
sqliteFree(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(MemPage *pPage){
int rc; /* Return value from subprocedures */
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 brk; /* Offset to content of first cell in parent */
assert( pPage->pParent==0 );
assert( pPage->nOverflow>0 );
pBt = pPage->pBt;
rc = allocatePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
if( rc ) return rc;
assert( sqlite3pager_iswriteable(pChild->aData) );
usableSize = pBt->usableSize;
data = pPage->aData;
hdr = pPage->hdrOffset;
brk = get2byte(&data[hdr+5]);
cdata = pChild->aData;
memcpy(cdata, &data[hdr], pPage->cellOffset+2*pPage->nCell-hdr);
memcpy(&cdata[brk], &data[brk], usableSize-brk);
assert( pChild->isInit==0 );
rc = initPage(pChild, pPage);
if( rc ) goto balancedeeper_out;
memcpy(pChild->aOvfl, pPage->aOvfl, pPage->nOverflow*sizeof(pPage->aOvfl[0]));
pChild->nOverflow = pPage->nOverflow;
if( pChild->nOverflow ){
pChild->nFree = 0;
}
assert( pChild->nCell==pPage->nCell );
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));
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
int i;
rc = ptrmapPut(pBt, pChild->pgno, PTRMAP_BTREE, pPage->pgno);
if( rc ) goto balancedeeper_out;
for(i=0; i<pChild->nCell; i++){
rc = ptrmapPutOvfl(pChild, i);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
#endif
rc = balance_nonroot(pChild);
balancedeeper_out:
releasePage(pChild);
return rc;
}
/*
** Decide if the page pPage needs to be balanced. If balancing is
** required, call the appropriate balancing routine.
*/
static int balance(MemPage *pPage, int insert){
int rc = SQLITE_OK;
if( pPage->pParent==0 ){
if( pPage->nOverflow>0 ){
rc = balance_deeper(pPage);
}
if( rc==SQLITE_OK && pPage->nCell==0 ){
rc = balance_shallower(pPage);
}
}else{
if( pPage->nOverflow>0 ||
(!insert && pPage->nFree>pPage->pBt->usableSize*2/3) ){
rc = balance_nonroot(pPage);
}
}
return rc;
}
/*
** This routine checks all cursors that point to table pgnoRoot.
** If any of those cursors other than pExclude were opened with
** wrFlag==0 then this routine returns SQLITE_LOCKED. If all
** cursors that point to pgnoRoot were opened with wrFlag==1
** then this routine returns SQLITE_OK.
**
** In addition to checking for read-locks (where a read-lock
** means a cursor opened with wrFlag==0) this routine also moves
** all cursors other than pExclude so that they are pointing to the
** first Cell on root page. This is necessary because an insert
** or delete might change the number of cells on a page or delete
** a page entirely and we do not want to leave any cursors
** pointing to non-existant pages or cells.
*/
static int checkReadLocks(BtShared *pBt, Pgno pgnoRoot, BtCursor *pExclude){
BtCursor *p;
for(p=pBt->pCursor; p; p=p->pNext){
u32 flags = (p->pBtree->pSqlite ? p->pBtree->pSqlite->flags : 0);
if( p->pgnoRoot!=pgnoRoot || p==pExclude ) continue;
if( p->wrFlag==0 && flags&SQLITE_ReadUncommitted ) continue;
if( p->wrFlag==0 ) return SQLITE_LOCKED;
if( p->pPage->pgno!=p->pgnoRoot ){
moveToRoot(p);
}
}
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 rc;
int loc;
int szNew;
MemPage *pPage;
BtShared *pBt = pCur->pBtree->pBt;
unsigned char *oldCell;
unsigned char *newCell = 0;
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction before doing an insert */
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( !pBt->readOnly );
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Cursor not open for writing */
}
if( checkReadLocks(pBt, pCur->pgnoRoot, pCur) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
/* Save the positions of any other cursors open on this table */
if(
SQLITE_OK!=(rc = restoreCursorPosition(pCur, 0)) ||
SQLITE_OK!=(rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur)) ||
SQLITE_OK!=(rc = sqlite3BtreeMoveto(pCur, pKey, nKey, &loc))
){
return rc;
}
pPage = pCur->pPage;
assert( pPage->intKey || nKey>=0 );
assert( pPage->leaf || !pPage->leafData );
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 );
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
newCell = sqliteMallocRaw( MX_CELL_SIZE(pBt) );
if( newCell==0 ) return SQLITE_NOMEM;
rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, &szNew);
if( rc ) goto end_insert;
assert( szNew==cellSizePtr(pPage, newCell) );
assert( szNew<=MX_CELL_SIZE(pBt) );
if( loc==0 && CURSOR_VALID==pCur->eState ){
int szOld;
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
oldCell = findCell(pPage, pCur->idx);
if( !pPage->leaf ){
memcpy(newCell, oldCell, 4);
}
szOld = cellSizePtr(pPage, oldCell);
rc = clearCell(pPage, oldCell);
if( rc ) goto end_insert;
dropCell(pPage, pCur->idx, szOld);
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->leaf );
pCur->idx++;
pCur->info.nSize = 0;
}else{
assert( pPage->leaf );
}
rc = insertCell(pPage, pCur->idx, newCell, szNew, 0, 0);
if( rc!=SQLITE_OK ) goto end_insert;
rc = balance(pPage, 1);
/* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */
/* fflush(stdout); */
if( rc==SQLITE_OK ){
moveToRoot(pCur);
}
end_insert:
sqliteFree(newCell);
return rc;
}
/*
** Delete the entry that the cursor is pointing to. The cursor
** is left pointing at a random location.
*/
int sqlite3BtreeDelete(BtCursor *pCur){
MemPage *pPage = pCur->pPage;
unsigned char *pCell;
int rc;
Pgno pgnoChild = 0;
BtShared *pBt = pCur->pBtree->pBt;
assert( pPage->isInit );
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction before doing a delete */
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( !pBt->readOnly );
if( pCur->idx >= 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(pBt, pCur->pgnoRoot, pCur) ){
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 sqlite3pager_write() on the page
** that the entry will be deleted from.
*/
if(
(rc = restoreCursorPosition(pCur, 1)) ||
(rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur)) ||
(rc = sqlite3pager_write(pPage->aData))
){
return rc;
}
/* Locate the cell within it's 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.
*/
pCell = findCell(pPage, pCur->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;
unsigned char *pNext;
int szNext;
int notUsed;
unsigned char *tempCell = 0;
assert( !pPage->leafData );
getTempCursor(pCur, &leafCur);
rc = sqlite3BtreeNext(&leafCur, &notUsed);
if( rc!=SQLITE_OK ){
if( rc!=SQLITE_NOMEM ){
rc = SQLITE_CORRUPT_BKPT;
}
}
if( rc==SQLITE_OK ){
rc = sqlite3pager_write(leafCur.pPage->aData);
}
if( rc==SQLITE_OK ){
TRACE(("DELETE: table=%d delete internal from %d replace from leaf %d\n",
pCur->pgnoRoot, pPage->pgno, leafCur.pPage->pgno));
dropCell(pPage, pCur->idx, cellSizePtr(pPage, pCell));
pNext = findCell(leafCur.pPage, leafCur.idx);
szNext = cellSizePtr(leafCur.pPage, pNext);
assert( MX_CELL_SIZE(pBt)>=szNext+4 );
tempCell = sqliteMallocRaw( MX_CELL_SIZE(pBt) );
if( tempCell==0 ){
rc = SQLITE_NOMEM;
}
}
if( rc==SQLITE_OK ){
rc = insertCell(pPage, pCur->idx, pNext-4, szNext+4, tempCell, 0);
}
if( rc==SQLITE_OK ){
put4byte(findOverflowCell(pPage, pCur->idx), pgnoChild);
rc = balance(pPage, 0);
}
if( rc==SQLITE_OK ){
dropCell(leafCur.pPage, leafCur.idx, szNext);
rc = balance(leafCur.pPage, 0);
}
sqliteFree(tempCell);
releaseTempCursor(&leafCur);
}else{
TRACE(("DELETE: table=%d delete from leaf %d\n",
pCur->pgnoRoot, pPage->pgno));
dropCell(pPage, pCur->idx, cellSizePtr(pPage, pCell));
rc = balance(pPage, 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
*/
int sqlite3BtreeCreateTable(Btree *p, int *piTable, int flags){
BtShared *pBt = p->pBt;
MemPage *pRoot;
Pgno pgnoRoot;
int rc;
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction first */
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( !pBt->readOnly );
/* It is illegal to create a table if any cursors are open on the
** database. This is because in auto-vacuum mode the backend may
** need to move a database page to make room for the new root-page.
** If an open cursor was using the page a problem would occur.
*/
if( pBt->pCursor ){
return SQLITE_LOCKED;
}
#ifdef SQLITE_OMIT_AUTOVACUUM
rc = allocatePage(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. */
/* 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.
*/
if( pgnoRoot==PTRMAP_PAGENO(pBt->usableSize, 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 = allocatePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, 1);
if( rc!=SQLITE_OK ){
return rc;
}
if( pgnoMove!=pgnoRoot ){
u8 eType;
Pgno iPtrPage;
releasePage(pPageMove);
rc = getPage(pBt, pgnoRoot, &pRoot);
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 = sqlite3pager_write(pRoot->aData);
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove);
releasePage(pRoot);
if( rc!=SQLITE_OK ){
return rc;
}
rc = getPage(pBt, pgnoRoot, &pRoot);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3pager_write(pRoot->aData);
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 = allocatePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ) return rc;
}
#endif
assert( sqlite3pager_iswriteable(pRoot->aData) );
zeroPage(pRoot, flags | PTF_LEAF);
sqlite3pager_unref(pRoot->aData);
*piTable = (int)pgnoRoot;
return SQLITE_OK;
}
/*
** 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 */
MemPage *pParent, /* Parent page. NULL for the root */
int freePageFlag /* Deallocate page if true */
){
MemPage *pPage = 0;
int rc;
unsigned char *pCell;
int i;
if( pgno>sqlite3pager_pagecount(pBt->pPager) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getAndInitPage(pBt, pgno, &pPage, pParent);
if( rc ) goto cleardatabasepage_out;
rc = sqlite3pager_write(pPage->aData);
if( rc ) goto cleardatabasepage_out;
for(i=0; i<pPage->nCell; i++){
pCell = findCell(pPage, i);
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(pCell), pPage->pParent, 1);
if( rc ) goto cleardatabasepage_out;
}
rc = clearCell(pPage, pCell);
if( rc ) goto cleardatabasepage_out;
}
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(&pPage->aData[8]), pPage->pParent, 1);
if( rc ) goto cleardatabasepage_out;
}
if( freePageFlag ){
rc = freePage(pPage);
}else{
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.
*/
int sqlite3BtreeClearTable(Btree *p, int iTable){
int rc;
BtCursor *pCur;
BtShared *pBt = p->pBt;
if( p->inTrans!=TRANS_WRITE ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pgnoRoot==(Pgno)iTable ){
if( pCur->wrFlag==0 ) return SQLITE_LOCKED;
moveToRoot(pCur);
}
}
rc = clearDatabasePage(pBt, (Pgno)iTable, 0, 0);
#if 0
if( rc ){
sqlite3BtreeRollback(pBt);
}
#endif
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.
*/
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
int rc;
MemPage *pPage = 0;
BtShared *pBt = p->pBt;
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 = getPage(pBt, (Pgno)iTable, &pPage);
if( rc ) return rc;
rc = sqlite3BtreeClearTable(p, iTable);
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 = getPage(pBt, maxRootPgno, &pMove);
if( rc!=SQLITE_OK ){
return rc;
}
rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
rc = getPage(pBt, maxRootPgno, &pMove);
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->usableSize, 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;
}
/*
** 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){
int rc;
unsigned char *pP1;
BtShared *pBt = p->pBt;
/* 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 ){
return rc;
}
assert( idx>=0 && idx<=15 );
rc = sqlite3pager_get(pBt->pPager, 1, (void**)&pP1);
if( rc ) return rc;
*pMeta = get4byte(&pP1[36 + idx*4]);
sqlite3pager_unref(pP1);
/* 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);
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 );
if( p->inTrans!=TRANS_WRITE ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( pBt->pPage1!=0 );
pP1 = pBt->pPage1->aData;
rc = sqlite3pager_write(pP1);
if( rc ) return rc;
put4byte(&pP1[36 + idx*4], iMeta);
return SQLITE_OK;
}
/*
** 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 = pCur->pPage;
return pPage ? pPage->aData[pPage->hdrOffset] : 0;
}
#ifdef SQLITE_DEBUG
/*
** Print a disassembly of the given page on standard output. This routine
** is used for debugging and testing only.
*/
static int btreePageDump(BtShared *pBt, int pgno, int recursive, MemPage *pParent){
int rc;
MemPage *pPage;
int i, j, c;
int nFree;
u16 idx;
int hdr;
int nCell;
int isInit;
unsigned char *data;
char range[20];
unsigned char payload[20];
rc = getPage(pBt, (Pgno)pgno, &pPage);
isInit = pPage->isInit;
if( pPage->isInit==0 ){
initPage(pPage, pParent);
}
if( rc ){
return rc;
}
hdr = pPage->hdrOffset;
data = pPage->aData;
c = data[hdr];
pPage->intKey = (c & (PTF_INTKEY|PTF_LEAFDATA))!=0;
pPage->zeroData = (c & PTF_ZERODATA)!=0;
pPage->leafData = (c & PTF_LEAFDATA)!=0;
pPage->leaf = (c & PTF_LEAF)!=0;
pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
nCell = get2byte(&data[hdr+3]);
sqlite3DebugPrintf("PAGE %d: flags=0x%02x frag=%d parent=%d\n", pgno,
data[hdr], data[hdr+7],
(pPage->isInit && pPage->pParent) ? pPage->pParent->pgno : 0);
assert( hdr == (pgno==1 ? 100 : 0) );
idx = hdr + 12 - pPage->leaf*4;
for(i=0; i<nCell; i++){
CellInfo info;
Pgno child;
unsigned char *pCell;
int sz;
int addr;
addr = get2byte(&data[idx + 2*i]);
pCell = &data[addr];
parseCellPtr(pPage, pCell, &info);
sz = info.nSize;
sprintf(range,"%d..%d", addr, addr+sz-1);
if( pPage->leaf ){
child = 0;
}else{
child = get4byte(pCell);
}
sz = info.nData;
if( !pPage->intKey ) sz += info.nKey;
if( sz>sizeof(payload)-1 ) sz = sizeof(payload)-1;
memcpy(payload, &pCell[info.nHeader], sz);
for(j=0; j<sz; j++){
if( payload[j]<0x20 || payload[j]>0x7f ) payload[j] = '.';
}
payload[sz] = 0;
sqlite3DebugPrintf(
"cell %2d: i=%-10s chld=%-4d nk=%-4lld nd=%-4d payload=%s\n",
i, range, child, info.nKey, info.nData, payload
);
}
if( !pPage->leaf ){
sqlite3DebugPrintf("right_child: %d\n", get4byte(&data[hdr+8]));
}
nFree = 0;
i = 0;
idx = get2byte(&data[hdr+1]);
while( idx>0 && idx<pPage->pBt->usableSize ){
int sz = get2byte(&data[idx+2]);
sprintf(range,"%d..%d", idx, idx+sz-1);
nFree += sz;
sqlite3DebugPrintf("freeblock %2d: i=%-10s size=%-4d total=%d\n",
i, range, sz, nFree);
idx = get2byte(&data[idx]);
i++;
}
if( idx!=0 ){
sqlite3DebugPrintf("ERROR: next freeblock index out of range: %d\n", idx);
}
if( recursive && !pPage->leaf ){
for(i=0; i<nCell; i++){
unsigned char *pCell = findCell(pPage, i);
btreePageDump(pBt, get4byte(pCell), 1, pPage);
idx = get2byte(pCell);
}
btreePageDump(pBt, get4byte(&data[hdr+8]), 1, pPage);
}
pPage->isInit = isInit;
sqlite3pager_unref(data);
fflush(stdout);
return SQLITE_OK;
}
int sqlite3BtreePageDump(Btree *p, int pgno, int recursive){
return btreePageDump(p->pBt, pgno, recursive, 0);
}
#endif
#ifdef SQLITE_TEST
/*
** Fill aResult[] with information about the entry and page that the
** cursor is pointing to.
**
** aResult[0] = The page number
** aResult[1] = The entry number
** aResult[2] = Total number of entries on this page
** aResult[3] = Cell size (local payload + header)
** aResult[4] = Number of free bytes on this page
** aResult[5] = Number of free blocks on the page
** aResult[6] = Total payload size (local + overflow)
** aResult[7] = Header size in bytes
** aResult[8] = Local payload size
** aResult[9] = Parent page number
**
** This routine is used for testing and debugging only.
*/
int sqlite3BtreeCursorInfo(BtCursor *pCur, int *aResult, int upCnt){
int cnt, idx;
MemPage *pPage = pCur->pPage;
BtCursor tmpCur;
int rc = restoreCursorPosition(pCur, 1);
if( rc!=SQLITE_OK ){
return rc;
}
pageIntegrity(pPage);
assert( pPage->isInit );
getTempCursor(pCur, &tmpCur);
while( upCnt-- ){
moveToParent(&tmpCur);
}
pPage = tmpCur.pPage;
pageIntegrity(pPage);
aResult[0] = sqlite3pager_pagenumber(pPage->aData);
assert( aResult[0]==pPage->pgno );
aResult[1] = tmpCur.idx;
aResult[2] = pPage->nCell;
if( tmpCur.idx>=0 && tmpCur.idx<pPage->nCell ){
getCellInfo(&tmpCur);
aResult[3] = tmpCur.info.nSize;
aResult[6] = tmpCur.info.nData;
aResult[7] = tmpCur.info.nHeader;
aResult[8] = tmpCur.info.nLocal;
}else{
aResult[3] = 0;
aResult[6] = 0;
aResult[7] = 0;
aResult[8] = 0;
}
aResult[4] = pPage->nFree;
cnt = 0;
idx = get2byte(&pPage->aData[pPage->hdrOffset+1]);
while( idx>0 && idx<pPage->pBt->usableSize ){
cnt++;
idx = get2byte(&pPage->aData[idx]);
}
aResult[5] = cnt;
if( pPage->pParent==0 || isRootPage(pPage) ){
aResult[9] = 0;
}else{
aResult[9] = pPage->pParent->pgno;
}
releaseTempCursor(&tmpCur);
return SQLITE_OK;
}
#endif
/*
** Return the pager associated with a BTree. This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *p){
return p->pBt->pPager;
}
/*
** This structure is passed around through all the sanity checking routines
** in order to keep track of some global state information.
*/
typedef struct IntegrityCk IntegrityCk;
struct IntegrityCk {
BtShared *pBt; /* The tree being checked out */
Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
int nPage; /* Number of pages in the database */
int *anRef; /* Number of times each page is referenced */
char *zErrMsg; /* An error message. NULL of no errors seen. */
};
#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;
char *zMsg2;
va_start(ap, zFormat);
zMsg2 = sqlite3VMPrintf(zFormat, ap);
va_end(ap);
if( zMsg1==0 ) zMsg1 = "";
if( pCheck->zErrMsg ){
char *zOld = pCheck->zErrMsg;
pCheck->zErrMsg = 0;
sqlite3SetString(&pCheck->zErrMsg, zOld, "\n", zMsg1, zMsg2, (char*)0);
sqliteFree(zOld);
}else{
sqlite3SetString(&pCheck->zErrMsg, zMsg1, zMsg2, (char*)0);
}
sqliteFree(zMsg2);
}
#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, int iPage, char *zContext){
if( iPage==0 ) return 1;
if( iPage>pCheck->nPage || iPage<0 ){
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 ){
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 ){
unsigned char *pOvfl;
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( sqlite3pager_get(pCheck->pPager, (Pgno)iPage, (void**)&pOvfl) ){
checkAppendMsg(pCheck, zContext, "failed to get page %d", iPage);
break;
}
if( isFreeList ){
int n = get4byte(&pOvfl[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0, zContext);
}
#endif
if( n>pCheck->pBt->usableSize/4-8 ){
checkAppendMsg(pCheck, zContext,
"freelist leaf count too big on page %d", iPage);
N--;
}else{
for(i=0; i<n; i++){
Pgno iFreePage = get4byte(&pOvfl[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(pOvfl);
checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage, zContext);
}
}
#endif
iPage = get4byte(pOvfl);
sqlite3pager_unref(pOvfl);
}
}
#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 */
MemPage *pParent, /* Parent page */
char *zParentContext, /* Parent context */
char *zLowerBound, /* All keys should be greater than this, if not NULL */
int nLower, /* Number of characters in zLowerBound */
char *zUpperBound, /* All keys should be less than this, if not NULL */
int nUpper /* Number of characters in zUpperBound */
){
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;
sprintf(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 = getPage(pBt, (Pgno)iPage, &pPage))!=0 ){
checkAppendMsg(pCheck, zContext,
"unable to get the page. error code=%d", rc);
return 0;
}
if( (rc = initPage(pPage, pParent))!=0 ){
checkAppendMsg(pCheck, zContext, "initPage() returns error code %d", rc);
releasePage(pPage);
return 0;
}
/* Check out all the cells.
*/
depth = 0;
for(i=0; i<pPage->nCell; i++){
u8 *pCell;
int sz;
CellInfo info;
/* Check payload overflow pages
*/
sprintf(zContext, "On tree page %d cell %d: ", iPage, i);
pCell = findCell(pPage,i);
parseCellPtr(pPage, pCell, &info);
sz = info.nData;
if( !pPage->intKey ) sz += info.nKey;
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,pPage,zContext,0,0,0,0);
if( i>0 && d2!=depth ){
checkAppendMsg(pCheck, zContext, "Child page depth differs");
}
depth = d2;
}
}
if( !pPage->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
sprintf(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, pPage, zContext,0,0,0,0);
}
/* Check for complete coverage of the page
*/
data = pPage->aData;
hdr = pPage->hdrOffset;
hit = sqliteMalloc( usableSize );
if( hit ){
memset(hit, 1, get2byte(&data[hdr+5]));
nCell = get2byte(&data[hdr+3]);
cellStart = hdr + 12 - 4*pPage->leaf;
for(i=0; i<nCell; i++){
int pc = get2byte(&data[cellStart+i*2]);
int size = cellSizePtr(pPage, &data[pc]);
int j;
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);
}
}
sqliteFree(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.
**
** If everything checks out, this routine returns NULL. If something is
** amiss, an error message is written into memory obtained from malloc()
** and a pointer to that error message is returned. The calling function
** is responsible for freeing the error message when it is done.
*/
char *sqlite3BtreeIntegrityCheck(Btree *p, int *aRoot, int nRoot){
int i;
int nRef;
IntegrityCk sCheck;
BtShared *pBt = p->pBt;
nRef = *sqlite3pager_stats(pBt->pPager);
if( lockBtreeWithRetry(p)!=SQLITE_OK ){
return sqliteStrDup("Unable to acquire a read lock on the database");
}
sCheck.pBt = pBt;
sCheck.pPager = pBt->pPager;
sCheck.nPage = sqlite3pager_pagecount(sCheck.pPager);
if( sCheck.nPage==0 ){
unlockBtreeIfUnused(pBt);
return 0;
}
sCheck.anRef = sqliteMallocRaw( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
if( !sCheck.anRef ){
unlockBtreeIfUnused(pBt);
return sqlite3MPrintf("Unable to malloc %d bytes",
(sCheck.nPage+1)*sizeof(sCheck.anRef[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;
}
sCheck.zErrMsg = 0;
/* 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; i<nRoot; 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], 0, "List of tree roots: ", 0,0,0,0);
}
/* Make sure every page in the file is referenced
*/
for(i=1; i<=sCheck.nPage; 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->usableSize, i)!=i || !pBt->autoVacuum) ){
checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
}
if( sCheck.anRef[i]!=0 &&
(PTRMAP_PAGENO(pBt->usableSize, 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 != *sqlite3pager_stats(pBt->pPager) ){
checkAppendMsg(&sCheck, 0,
"Outstanding page count goes from %d to %d during this analysis",
nRef, *sqlite3pager_stats(pBt->pPager)
);
}
/* Clean up and report errors.
*/
sqliteFree(sCheck.anRef);
return sCheck.zErrMsg;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3pager_filename(p->pBt->pPager);
}
/*
** Return the pathname of the directory that contains the database file.
*/
const char *sqlite3BtreeGetDirname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3pager_dirname(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.
*/
const char *sqlite3BtreeGetJournalname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3pager_journalname(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 pBtFrom may be reduced by this operation.
** If anything goes wrong, the transaction on pBtFrom is rolled back.
*/
int sqlite3BtreeCopyFile(Btree *pTo, Btree *pFrom){
int rc = SQLITE_OK;
Pgno i, nPage, nToPage, iSkip;
BtShared *pBtTo = pTo->pBt;
BtShared *pBtFrom = pFrom->pBt;
if( pTo->inTrans!=TRANS_WRITE || pFrom->inTrans!=TRANS_WRITE ){
return SQLITE_ERROR;
}
if( pBtTo->pCursor ) return SQLITE_BUSY;
nToPage = sqlite3pager_pagecount(pBtTo->pPager);
nPage = sqlite3pager_pagecount(pBtFrom->pPager);
iSkip = PENDING_BYTE_PAGE(pBtTo);
for(i=1; rc==SQLITE_OK && i<=nPage; i++){
void *pPage;
if( i==iSkip ) continue;
rc = sqlite3pager_get(pBtFrom->pPager, i, &pPage);
if( rc ) break;
rc = sqlite3pager_overwrite(pBtTo->pPager, i, pPage);
if( rc ) break;
sqlite3pager_unref(pPage);
}
for(i=nPage+1; rc==SQLITE_OK && i<=nToPage; i++){
void *pPage;
if( i==iSkip ) continue;
rc = sqlite3pager_get(pBtTo->pPager, i, &pPage);
if( rc ) break;
rc = sqlite3pager_write(pPage);
sqlite3pager_unref(pPage);
sqlite3pager_dont_write(pBtTo->pPager, i);
}
if( !rc && nPage<nToPage ){
rc = sqlite3pager_truncate(pBtTo->pPager, nPage);
}
if( rc ){
sqlite3BtreeRollback(pTo);
}
return rc;
}
#endif /* SQLITE_OMIT_VACUUM */
/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *p){
return (p && (p->inTrans==TRANS_WRITE));
}
/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *p){
return (p->pBt && p->pBt->inStmt);
}
/*
** 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 sqlite3BtreeSync(Btree *p, const char *zMaster){
if( p->inTrans==TRANS_WRITE ){
BtShared *pBt = p->pBt;
#ifndef SQLITE_OMIT_AUTOVACUUM
Pgno nTrunc = 0;
if( pBt->autoVacuum ){
int rc = autoVacuumCommit(pBt, &nTrunc);
if( rc!=SQLITE_OK ) return rc;
}
return sqlite3pager_sync(pBt->pPager, zMaster, nTrunc);
#endif
return sqlite3pager_sync(pBt->pPager, zMaster, 0);
}
return SQLITE_OK;
}
/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for it's 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.
**
** 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 sqliteFree()
** on the memory, the btree layer does that.
*/
void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
BtShared *pBt = p->pBt;
if( !pBt->pSchema ){
pBt->pSchema = sqliteMalloc(nBytes);
pBt->xFreeSchema = xFree;
}
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){
return (queryTableLock(p, MASTER_ROOT, READ_LOCK)!=SQLITE_OK);
}
int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
int rc = SQLITE_OK;
#ifndef SQLITE_OMIT_SHARED_CACHE
u8 lockType = (isWriteLock?WRITE_LOCK:READ_LOCK);
rc = queryTableLock(p, iTab, lockType);
if( rc==SQLITE_OK ){
rc = lockTable(p, iTab, lockType);
}
#endif
return rc;
}
#if defined(SQLITE_TEST) && !defined(NO_TCL)
#include <tcl.h>
int sqlite3_shared_cache_report(
void * clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
ThreadData *pTd = sqlite3ThreadData();
if( pTd->useSharedData ){
BtShared *pBt;
Tcl_Obj *pRet = Tcl_NewObj();
for(pBt=pTd->pBtree; pBt; pBt=pBt->pNext){
const char *zFile = sqlite3pager_filename(pBt->pPager);
Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj(zFile, -1));
Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(pBt->nRef));
}
Tcl_SetObjResult(interp, pRet);
}
return TCL_OK;
}
#endif