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gerrit.openfyde.cn / chromium.googlesource.com / chromium / deps / sqlite / bbce338412255f7aa5539c2bc6575f954d1ccae4 / . / src / pager.c
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/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** This is the implementation of the page cache subsystem or "pager".
**
** The pager is used to access a database disk file. It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file. The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.510 2008/11/29 22:49:23 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
/*
** Macros for troubleshooting. Normally turned off
*/
#if 0
#define sqlite3DebugPrintf printf
#define PAGERTRACE1(X) sqlite3DebugPrintf(X)
#define PAGERTRACE2(X,Y) sqlite3DebugPrintf(X,Y)
#define PAGERTRACE3(X,Y,Z) sqlite3DebugPrintf(X,Y,Z)
#define PAGERTRACE4(X,Y,Z,W) sqlite3DebugPrintf(X,Y,Z,W)
#define PAGERTRACE5(X,Y,Z,W,V) sqlite3DebugPrintf(X,Y,Z,W,V)
#else
#define PAGERTRACE1(X)
#define PAGERTRACE2(X,Y)
#define PAGERTRACE3(X,Y,Z)
#define PAGERTRACE4(X,Y,Z,W)
#define PAGERTRACE5(X,Y,Z,W,V)
#endif
/*
** The following two macros are used within the PAGERTRACEX() macros above
** to print out file-descriptors.
**
** PAGERID() takes a pointer to a Pager struct as its argument. The
** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
** struct as its argument.
*/
#define PAGERID(p) ((int)(p->fd))
#define FILEHANDLEID(fd) ((int)fd)
/*
** The page cache as a whole is always in one of the following
** states:
**
** PAGER_UNLOCK The page cache is not currently reading or
** writing the database file. There is no
** data held in memory. This is the initial
** state.
**
** PAGER_SHARED The page cache is reading the database.
** Writing is not permitted. There can be
** multiple readers accessing the same database
** file at the same time.
**
** PAGER_RESERVED This process has reserved the database for writing
** but has not yet made any changes. Only one process
** at a time can reserve the database. The original
** database file has not been modified so other
** processes may still be reading the on-disk
** database file.
**
** PAGER_EXCLUSIVE The page cache is writing the database.
** Access is exclusive. No other processes or
** threads can be reading or writing while one
** process is writing.
**
** PAGER_SYNCED The pager moves to this state from PAGER_EXCLUSIVE
** after all dirty pages have been written to the
** database file and the file has been synced to
** disk. All that remains to do is to remove or
** truncate the journal file and the transaction
** will be committed.
**
** The page cache comes up in PAGER_UNLOCK. The first time a
** sqlite3PagerGet() occurs, the state transitions to PAGER_SHARED.
** After all pages have been released using sqlite_page_unref(),
** the state transitions back to PAGER_UNLOCK. The first time
** that sqlite3PagerWrite() is called, the state transitions to
** PAGER_RESERVED. (Note that sqlite3PagerWrite() can only be
** called on an outstanding page which means that the pager must
** be in PAGER_SHARED before it transitions to PAGER_RESERVED.)
** PAGER_RESERVED means that there is an open rollback journal.
** The transition to PAGER_EXCLUSIVE occurs before any changes
** are made to the database file, though writes to the rollback
** journal occurs with just PAGER_RESERVED. After an sqlite3PagerRollback()
** or sqlite3PagerCommitPhaseTwo(), the state can go back to PAGER_SHARED,
** or it can stay at PAGER_EXCLUSIVE if we are in exclusive access mode.
*/
#define PAGER_UNLOCK 0
#define PAGER_SHARED 1 /* same as SHARED_LOCK */
#define PAGER_RESERVED 2 /* same as RESERVED_LOCK */
#define PAGER_EXCLUSIVE 4 /* same as EXCLUSIVE_LOCK */
#define PAGER_SYNCED 5
/*
** If the SQLITE_BUSY_RESERVED_LOCK macro is set to true at compile-time,
** then failed attempts to get a reserved lock will invoke the busy callback.
** This is off by default. To see why, consider the following scenario:
**
** Suppose thread A already has a shared lock and wants a reserved lock.
** Thread B already has a reserved lock and wants an exclusive lock. If
** both threads are using their busy callbacks, it might be a long time
** be for one of the threads give up and allows the other to proceed.
** But if the thread trying to get the reserved lock gives up quickly
** (if it never invokes its busy callback) then the contention will be
** resolved quickly.
*/
#ifndef SQLITE_BUSY_RESERVED_LOCK
# define SQLITE_BUSY_RESERVED_LOCK 0
#endif
/*
** This macro rounds values up so that if the value is an address it
** is guaranteed to be an address that is aligned to an 8-byte boundary.
*/
#define FORCE_ALIGNMENT(X) (((X)+7)&~7)
/*
** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC
# define CODEC1(P,D,N,X) if( P->xCodec!=0 ){ P->xCodec(P->pCodecArg,D,N,X); }
# define CODEC2(P,D,N,X) ((char*)(P->xCodec!=0?P->xCodec(P->pCodecArg,D,N,X):D))
#else
# define CODEC1(P,D,N,X) /* NO-OP */
# define CODEC2(P,D,N,X) ((char*)D)
#endif
/*
** A open page cache is an instance of the following structure.
**
** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or
** or SQLITE_FULL. Once one of the first three errors occurs, it persists
** and is returned as the result of every major pager API call. The
** SQLITE_FULL return code is slightly different. It persists only until the
** next successful rollback is performed on the pager cache. Also,
** SQLITE_FULL does not affect the sqlite3PagerGet() and sqlite3PagerLookup()
** APIs, they may still be used successfully.
*/
struct Pager {
sqlite3_vfs *pVfs; /* OS functions to use for IO */
u8 journalOpen; /* True if journal file descriptors is valid */
u8 journalStarted; /* True if header of journal is synced */
u8 useJournal; /* Use a rollback journal on this file */
u8 noReadlock; /* Do not bother to obtain readlocks */
u8 stmtOpen; /* True if the statement subjournal is open */
u8 stmtInUse; /* True we are in a statement subtransaction */
u8 stmtAutoopen; /* Open stmt journal when main journal is opened*/
u8 noSync; /* Do not sync the journal if true */
u8 fullSync; /* Do extra syncs of the journal for robustness */
u8 sync_flags; /* One of SYNC_NORMAL or SYNC_FULL */
u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */
u8 tempFile; /* zFilename is a temporary file */
u8 readOnly; /* True for a read-only database */
u8 needSync; /* True if an fsync() is needed on the journal */
u8 dirtyCache; /* True if cached pages have changed */
u8 alwaysRollback; /* Disable DontRollback() for all pages */
u8 memDb; /* True to inhibit all file I/O */
u8 setMaster; /* True if a m-j name has been written to jrnl */
u8 doNotSync; /* Boolean. While true, do not spill the cache */
u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
u8 journalMode; /* On of the PAGER_JOURNALMODE_* values */
u8 dbModified; /* True if there are any changes to the Db */
u8 changeCountDone; /* Set after incrementing the change-counter */
u8 dbSizeValid; /* Set when dbSize is correct */
u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */
int errCode; /* One of several kinds of errors */
Pgno dbSize; /* Number of pages in the file */
Pgno origDbSize; /* dbSize before the current change */
Pgno stmtSize; /* Size of database (in pages) at stmt_begin() */
int nRec; /* Number of pages written to the journal */
u32 cksumInit; /* Quasi-random value added to every checksum */
int stmtNRec; /* Number of records in stmt subjournal */
int nExtra; /* Add this many bytes to each in-memory page */
int pageSize; /* Number of bytes in a page */
int nPage; /* Total number of in-memory pages */
int mxPage; /* Maximum number of pages to hold in cache */
Pgno mxPgno; /* Maximum allowed size of the database */
Bitvec *pInJournal; /* One bit for each page in the database file */
Bitvec *pInStmt; /* One bit for each page in the database */
Bitvec *pAlwaysRollback; /* One bit for each page marked always-rollback */
char *zFilename; /* Name of the database file */
char *zJournal; /* Name of the journal file */
char *zDirectory; /* Directory hold database and journal files */
sqlite3_file *fd, *jfd; /* File descriptors for database and journal */
sqlite3_file *stfd; /* File descriptor for the statement subjournal*/
int (*xBusyHandler)(void*); /* Function to call when busy */
void *pBusyHandlerArg; /* Context argument for xBusyHandler */
i64 journalOff; /* Current byte offset in the journal file */
i64 journalHdr; /* Byte offset to previous journal header */
i64 stmtHdrOff; /* First journal header written this statement */
i64 stmtCksum; /* cksumInit when statement was started */
i64 stmtJSize; /* Size of journal at stmt_begin() */
u32 sectorSize; /* Assumed sector size during rollback */
#ifdef SQLITE_TEST
int nHit, nMiss; /* Cache hits and missing */
int nRead, nWrite; /* Database pages read/written */
#endif
void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
#ifdef SQLITE_HAS_CODEC
void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
void *pCodecArg; /* First argument to xCodec() */
#endif
char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */
char dbFileVers[16]; /* Changes whenever database file changes */
i64 journalSizeLimit; /* Size limit for persistent journal files */
PCache *pPCache; /* Pointer to page cache object */
};
/*
** The following global variables hold counters used for
** testing purposes only. These variables do not exist in
** a non-testing build. These variables are not thread-safe.
*/
#ifdef SQLITE_TEST
int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */
int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */
int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */
# define PAGER_INCR(v) v++
#else
# define PAGER_INCR(v)
#endif
/*
** Journal files begin with the following magic string. The data
** was obtained from /dev/random. It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
** checking information. If the power fails while the journal is begin
** written, semi-random garbage data might appear in the journal
** file after power is restored. If an attempt is then made
** to roll the journal back, the database could be corrupted. The additional
** sanity checking data is an attempt to discover the garbage in the
** journal and ignore it.
**
** The sanity checking information for the new journal format consists
** of a 32-bit checksum on each page of data. The checksum covers both
** the page number and the pPager->pageSize bytes of data for the page.
** This cksum is initialized to a 32-bit random value that appears in the
** journal file right after the header. The random initializer is important,
** because garbage data that appears at the end of a journal is likely
** data that was once in other files that have now been deleted. If the
** garbage data came from an obsolete journal file, the checksums might
** be correct. But by initializing the checksum to random value which
** is different for every journal, we minimize that risk.
*/
static const unsigned char aJournalMagic[] = {
0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
};
/*
** The size of the header and of each page in the journal is determined
** by the following macros.
*/
#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8)
/*
** The journal header size for this pager. In the future, this could be
** set to some value read from the disk controller. The important
** characteristic is that it is the same size as a disk sector.
*/
#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
/*
** The macro MEMDB is true if we are dealing with an in-memory database.
** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
** the value of MEMDB will be a constant and the compiler will optimize
** out code that would never execute.
*/
#ifdef SQLITE_OMIT_MEMORYDB
# define MEMDB 0
#else
# define MEMDB pPager->memDb
#endif
/*
** Page number PAGER_MJ_PGNO is never used in an SQLite database (it is
** reserved for working around a windows/posix incompatibility). It is
** used in the journal to signify that the remainder of the journal file
** is devoted to storing a master journal name - there are no more pages to
** roll back. See comments for function writeMasterJournal() for details.
*/
/* #define PAGER_MJ_PGNO(x) (PENDING_BYTE/((x)->pageSize)) */
#define PAGER_MJ_PGNO(x) ((Pgno)((PENDING_BYTE/((x)->pageSize))+1))
/*
** The maximum legal page number is (2^31 - 1).
*/
#define PAGER_MAX_PGNO 2147483647
/*
** Return true if page *pPg has already been written to the statement
** journal (or statement snapshot has been created, if *pPg is part
** of an in-memory database).
*/
static int pageInStatement(PgHdr *pPg){
Pager *pPager = pPg->pPager;
return sqlite3BitvecTest(pPager->pInStmt, pPg->pgno);
}
static int pageInJournal(PgHdr *pPg){
return sqlite3BitvecTest(pPg->pPager->pInJournal, pPg->pgno);
}
/*
** Read a 32-bit integer from the given file descriptor. Store the integer
** that is read in *pRes. Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
*/
static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
unsigned char ac[4];
int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
if( rc==SQLITE_OK ){
*pRes = sqlite3Get4byte(ac);
}
return rc;
}
/*
** Write a 32-bit integer into a string buffer in big-endian byte order.
*/
#define put32bits(A,B) sqlite3Put4byte((u8*)A,B)
/*
** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK
** on success or an error code is something goes wrong.
*/
static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
char ac[4];
put32bits(ac, val);
return sqlite3OsWrite(fd, ac, 4, offset);
}
/*
** If file pFd is open, call sqlite3OsUnlock() on it.
*/
static int osUnlock(sqlite3_file *pFd, int eLock){
if( !pFd->pMethods ){
return SQLITE_OK;
}
return sqlite3OsUnlock(pFd, eLock);
}
/*
** This function determines whether or not the atomic-write optimization
** can be used with this pager. The optimization can be used if:
**
** (a) the value returned by OsDeviceCharacteristics() indicates that
** a database page may be written atomically, and
** (b) the value returned by OsSectorSize() is less than or equal
** to the page size.
**
** If the optimization cannot be used, 0 is returned. If it can be used,
** then the value returned is the size of the journal file when it
** contains rollback data for exactly one page.
*/
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
static int jrnlBufferSize(Pager *pPager){
int dc; /* Device characteristics */
int nSector; /* Sector size */
int szPage; /* Page size */
sqlite3_file *fd = pPager->fd;
if( fd->pMethods ){
dc = sqlite3OsDeviceCharacteristics(fd);
nSector = sqlite3OsSectorSize(fd);
szPage = pPager->pageSize;
}
assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
if( !fd->pMethods ||
(dc & (SQLITE_IOCAP_ATOMIC|(szPage>>8)) && nSector<=szPage) ){
return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
}
return 0;
}
#endif
/*
** This function should be called when an error occurs within the pager
** code. The first argument is a pointer to the pager structure, the
** second the error-code about to be returned by a pager API function.
** The value returned is a copy of the second argument to this function.
**
** If the second argument is SQLITE_IOERR, SQLITE_CORRUPT, or SQLITE_FULL
** the error becomes persistent. Until the persisten error is cleared,
** subsequent API calls on this Pager will immediately return the same
** error code.
**
** A persistent error indicates that the contents of the pager-cache
** cannot be trusted. This state can be cleared by completely discarding
** the contents of the pager-cache. If a transaction was active when
** the persistent error occured, then the rollback journal may need
** to be replayed.
*/
static void pager_unlock(Pager *pPager);
static int pager_error(Pager *pPager, int rc){
int rc2 = rc & 0xff;
assert(
pPager->errCode==SQLITE_FULL ||
pPager->errCode==SQLITE_OK ||
(pPager->errCode & 0xff)==SQLITE_IOERR
);
if(
rc2==SQLITE_FULL ||
rc2==SQLITE_IOERR ||
rc2==SQLITE_CORRUPT
){
pPager->errCode = rc;
if( pPager->state==PAGER_UNLOCK
&& sqlite3PcacheRefCount(pPager->pPCache)==0
){
/* If the pager is already unlocked, call pager_unlock() now to
** clear the error state and ensure that the pager-cache is
** completely empty.
*/
pager_unlock(pPager);
}
}
return rc;
}
/*
** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
** on the cache using a hash function. This is used for testing
** and debugging only.
*/
#ifdef SQLITE_CHECK_PAGES
/*
** Return a 32-bit hash of the page data for pPage.
*/
static u32 pager_datahash(int nByte, unsigned char *pData){
u32 hash = 0;
int i;
for(i=0; i<nByte; i++){
hash = (hash*1039) + pData[i];
}
return hash;
}
static u32 pager_pagehash(PgHdr *pPage){
return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
}
static void pager_set_pagehash(PgHdr *pPage){
pPage->pageHash = pager_pagehash(pPage);
}
/*
** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
** is defined, and NDEBUG is not defined, an assert() statement checks
** that the page is either dirty or still matches the calculated page-hash.
*/
#define CHECK_PAGE(x) checkPage(x)
static void checkPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
assert( !pPg->pageHash || pPager->errCode
|| (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
}
#else
#define pager_datahash(X,Y) 0
#define pager_pagehash(X) 0
#define CHECK_PAGE(x)
#endif /* SQLITE_CHECK_PAGES */
/*
** When this is called the journal file for pager pPager must be open.
** The master journal file name is read from the end of the file and
** written into memory supplied by the caller.
**
** zMaster must point to a buffer of at least nMaster bytes allocated by
** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
** enough space to write the master journal name). If the master journal
** name in the journal is longer than nMaster bytes (including a
** nul-terminator), then this is handled as if no master journal name
** were present in the journal.
**
** If no master journal file name is present zMaster[0] is set to 0 and
** SQLITE_OK returned.
*/
static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){
int rc;
u32 len;
i64 szJ;
u32 cksum;
u32 u; /* Unsigned loop counter */
unsigned char aMagic[8]; /* A buffer to hold the magic header */
zMaster[0] = '\0';
rc = sqlite3OsFileSize(pJrnl, &szJ);
if( rc!=SQLITE_OK || szJ<16 ) return rc;
rc = read32bits(pJrnl, szJ-16, &len);
if( rc!=SQLITE_OK ) return rc;
if( len>=nMaster ){
return SQLITE_OK;
}
rc = read32bits(pJrnl, szJ-12, &cksum);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8);
if( rc!=SQLITE_OK || memcmp(aMagic, aJournalMagic, 8) ) return rc;
rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len);
if( rc!=SQLITE_OK ){
return rc;
}
zMaster[len] = '\0';
/* See if the checksum matches the master journal name */
for(u=0; u<len; u++){
cksum -= zMaster[u];
}
if( cksum ){
/* If the checksum doesn't add up, then one or more of the disk sectors
** containing the master journal filename is corrupted. This means
** definitely roll back, so just return SQLITE_OK and report a (nul)
** master-journal filename.
*/
zMaster[0] = '\0';
}
return SQLITE_OK;
}
/*
** Seek the journal file descriptor to the next sector boundary where a
** journal header may be read or written. Pager.journalOff is updated with
** the new seek offset.
**
** i.e for a sector size of 512:
**
** Input Offset Output Offset
** ---------------------------------------
** 0 0
** 512 512
** 100 512
** 2000 2048
**
*/
static void seekJournalHdr(Pager *pPager){
i64 offset = 0;
i64 c = pPager->journalOff;
if( c ){
offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
}
assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
assert( offset>=c );
assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
pPager->journalOff = offset;
}
/*
** Write zeros over the header of the journal file. This has the
** effect of invalidating the journal file and committing the
** transaction.
*/
static int zeroJournalHdr(Pager *pPager, int doTruncate){
int rc = SQLITE_OK;
static const char zeroHdr[28] = {0};
if( pPager->journalOff ){
i64 iLimit = pPager->journalSizeLimit;
IOTRACE(("JZEROHDR %p\n", pPager))
if( doTruncate || iLimit==0 ){
rc = sqlite3OsTruncate(pPager->jfd, 0);
}else{
rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
}
if( rc==SQLITE_OK && !pPager->noSync ){
rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->sync_flags);
}
/* At this point the transaction is committed but the write lock
** is still held on the file. If there is a size limit configured for
** the persistent journal and the journal file currently consumes more
** space than that limit allows for, truncate it now. There is no need
** to sync the file following this operation.
*/
if( rc==SQLITE_OK && iLimit>0 ){
i64 sz;
rc = sqlite3OsFileSize(pPager->jfd, &sz);
if( rc==SQLITE_OK && sz>iLimit ){
rc = sqlite3OsTruncate(pPager->jfd, iLimit);
}
}
}
return rc;
}
/*
** The journal file must be open when this routine is called. A journal
** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
** current location.
**
** The format for the journal header is as follows:
** - 8 bytes: Magic identifying journal format.
** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
** - 4 bytes: Random number used for page hash.
** - 4 bytes: Initial database page count.
** - 4 bytes: Sector size used by the process that wrote this journal.
** - 4 bytes: Database page size.
**
** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
*/
static int writeJournalHdr(Pager *pPager){
int rc = SQLITE_OK;
char *zHeader = pPager->pTmpSpace;
u32 nHeader = pPager->pageSize;
u32 nWrite;
if( nHeader>JOURNAL_HDR_SZ(pPager) ){
nHeader = JOURNAL_HDR_SZ(pPager);
}
if( pPager->stmtHdrOff==0 ){
pPager->stmtHdrOff = pPager->journalOff;
}
seekJournalHdr(pPager);
pPager->journalHdr = pPager->journalOff;
memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
/*
** Write the nRec Field - the number of page records that follow this
** journal header. Normally, zero is written to this value at this time.
** After the records are added to the journal (and the journal synced,
** if in full-sync mode), the zero is overwritten with the true number
** of records (see syncJournal()).
**
** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
** reading the journal this value tells SQLite to assume that the
** rest of the journal file contains valid page records. This assumption
** is dangerous, as if a failure occured whilst writing to the journal
** file it may contain some garbage data. There are two scenarios
** where this risk can be ignored:
**
** * When the pager is in no-sync mode. Corruption can follow a
** power failure in this case anyway.
**
** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
** that garbage data is never appended to the journal file.
*/
assert(pPager->fd->pMethods||pPager->noSync);
if( (pPager->noSync) || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
|| (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
){
put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
}else{
put32bits(&zHeader[sizeof(aJournalMagic)], 0);
}
/* The random check-hash initialiser */
sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
/* The initial database size */
put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbSize);
/* The assumed sector size for this process */
put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
/* Initializing the tail of the buffer is not necessary. Everything
** works find if the following memset() is omitted. But initializing
** the memory prevents valgrind from complaining, so we are willing to
** take the performance hit.
*/
memset(&zHeader[sizeof(aJournalMagic)+16], 0,
nHeader-(sizeof(aJournalMagic)+16));
if( pPager->journalHdr==0 ){
/* The page size */
put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
}
for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
pPager->journalOff += nHeader;
}
return rc;
}
/*
** The journal file must be open when this is called. A journal header file
** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
** file. See comments above function writeJournalHdr() for a description of
** the journal header format.
**
** If the header is read successfully, *nRec is set to the number of
** page records following this header and *dbSize is set to the size of the
** database before the transaction began, in pages. Also, pPager->cksumInit
** is set to the value read from the journal header. SQLITE_OK is returned
** in this case.
**
** If the journal header file appears to be corrupted, SQLITE_DONE is
** returned and *nRec and *dbSize are not set. If JOURNAL_HDR_SZ bytes
** cannot be read from the journal file an error code is returned.
*/
static int readJournalHdr(
Pager *pPager,
i64 journalSize,
u32 *pNRec,
u32 *pDbSize
){
int rc;
unsigned char aMagic[8]; /* A buffer to hold the magic header */
i64 jrnlOff;
int iPageSize;
seekJournalHdr(pPager);
if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
return SQLITE_DONE;
}
jrnlOff = pPager->journalOff;
rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), jrnlOff);
if( rc ) return rc;
jrnlOff += sizeof(aMagic);
if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
return SQLITE_DONE;
}
rc = read32bits(pPager->jfd, jrnlOff, pNRec);
if( rc ) return rc;
rc = read32bits(pPager->jfd, jrnlOff+4, &pPager->cksumInit);
if( rc ) return rc;
rc = read32bits(pPager->jfd, jrnlOff+8, pDbSize);
if( rc ) return rc;
rc = read32bits(pPager->jfd, jrnlOff+16, (u32 *)&iPageSize);
if( rc==SQLITE_OK
&& iPageSize>=512
&& iPageSize<=SQLITE_MAX_PAGE_SIZE
&& ((iPageSize-1)&iPageSize)==0
){
u16 pagesize = iPageSize;
rc = sqlite3PagerSetPagesize(pPager, &pagesize);
}
if( rc ) return rc;
/* Update the assumed sector-size to match the value used by
** the process that created this journal. If this journal was
** created by a process other than this one, then this routine
** is being called from within pager_playback(). The local value
** of Pager.sectorSize is restored at the end of that routine.
*/
rc = read32bits(pPager->jfd, jrnlOff+12, &pPager->sectorSize);
if( rc ) return rc;
if( (pPager->sectorSize & (pPager->sectorSize-1))!=0
|| pPager->sectorSize>0x1000000 ){
return SQLITE_DONE;
}
pPager->journalOff += JOURNAL_HDR_SZ(pPager);
return SQLITE_OK;
}
/*
** Write the supplied master journal name into the journal file for pager
** pPager at the current location. The master journal name must be the last
** thing written to a journal file. If the pager is in full-sync mode, the
** journal file descriptor is advanced to the next sector boundary before
** anything is written. The format is:
**
** + 4 bytes: PAGER_MJ_PGNO.
** + N bytes: length of master journal name.
** + 4 bytes: N
** + 4 bytes: Master journal name checksum.
** + 8 bytes: aJournalMagic[].
**
** The master journal page checksum is the sum of the bytes in the master
** journal name.
**
** If zMaster is a NULL pointer (occurs for a single database transaction),
** this call is a no-op.
*/
static int writeMasterJournal(Pager *pPager, const char *zMaster){
int rc;
int len;
int i;
i64 jrnlOff;
i64 jrnlSize;
u32 cksum = 0;
char zBuf[sizeof(aJournalMagic)+2*4];
if( !zMaster || pPager->setMaster ) return SQLITE_OK;
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ) return SQLITE_OK;
pPager->setMaster = 1;
len = strlen(zMaster);
for(i=0; i<len; i++){
cksum += zMaster[i];
}
/* If in full-sync mode, advance to the next disk sector before writing
** the master journal name. This is in case the previous page written to
** the journal has already been synced.
*/
if( pPager->fullSync ){
seekJournalHdr(pPager);
}
jrnlOff = pPager->journalOff;
pPager->journalOff += (len+20);
rc = write32bits(pPager->jfd, jrnlOff, PAGER_MJ_PGNO(pPager));
if( rc!=SQLITE_OK ) return rc;
jrnlOff += 4;
rc = sqlite3OsWrite(pPager->jfd, zMaster, len, jrnlOff);
if( rc!=SQLITE_OK ) return rc;
jrnlOff += len;
put32bits(zBuf, len);
put32bits(&zBuf[4], cksum);
memcpy(&zBuf[8], aJournalMagic, sizeof(aJournalMagic));
rc = sqlite3OsWrite(pPager->jfd, zBuf, 8+sizeof(aJournalMagic), jrnlOff);
jrnlOff += 8+sizeof(aJournalMagic);
pPager->needSync = !pPager->noSync;
/* If the pager is in peristent-journal mode, then the physical
** journal-file may extend past the end of the master-journal name
** and 8 bytes of magic data just written to the file. This is
** dangerous because the code to rollback a hot-journal file
** will not be able to find the master-journal name to determine
** whether or not the journal is hot.
**
** Easiest thing to do in this scenario is to truncate the journal
** file to the required size.
*/
if( (rc==SQLITE_OK)
&& (rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))==SQLITE_OK
&& jrnlSize>jrnlOff
){
rc = sqlite3OsTruncate(pPager->jfd, jrnlOff);
}
return rc;
}
/*
** Find a page in the hash table given its page number. Return
** a pointer to the page or NULL if not found.
*/
static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
PgHdr *p;
sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p);
return p;
}
/*
** Clear the in-memory cache. This routine
** sets the state of the pager back to what it was when it was first
** opened. Any outstanding pages are invalidated and subsequent attempts
** to access those pages will likely result in a coredump.
*/
static void pager_reset(Pager *pPager){
if( pPager->errCode ) return;
sqlite3PcacheClear(pPager->pPCache);
}
/*
** Unlock the database file.
**
** If the pager is currently in error state, discard the contents of
** the cache and reset the Pager structure internal state. If there is
** an open journal-file, then the next time a shared-lock is obtained
** on the pager file (by this or any other process), it will be
** treated as a hot-journal and rolled back.
*/
static void pager_unlock(Pager *pPager){
if( !pPager->exclusiveMode ){
int rc = osUnlock(pPager->fd, NO_LOCK);
if( rc ) pPager->errCode = rc;
pPager->dbSizeValid = 0;
IOTRACE(("UNLOCK %p\n", pPager))
/* Always close the journal file when dropping the database lock.
** Otherwise, another connection with journal_mode=delete might
** delete the file out from under us.
*/
if( pPager->journalOpen ){
sqlite3OsClose(pPager->jfd);
pPager->journalOpen = 0;
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
sqlite3BitvecDestroy(pPager->pAlwaysRollback);
pPager->pAlwaysRollback = 0;
}
/* If Pager.errCode is set, the contents of the pager cache cannot be
** trusted. Now that the pager file is unlocked, the contents of the
** cache can be discarded and the error code safely cleared.
*/
if( pPager->errCode ){
if( rc==SQLITE_OK ) pPager->errCode = SQLITE_OK;
pager_reset(pPager);
if( pPager->stmtOpen ){
sqlite3OsClose(pPager->stfd);
sqlite3BitvecDestroy(pPager->pInStmt);
pPager->pInStmt = 0;
}
pPager->stmtOpen = 0;
pPager->stmtInUse = 0;
pPager->journalOff = 0;
pPager->journalStarted = 0;
pPager->stmtAutoopen = 0;
pPager->origDbSize = 0;
}
pPager->state = PAGER_UNLOCK;
pPager->changeCountDone = 0;
}
}
/*
** Execute a rollback if a transaction is active and unlock the
** database file. If the pager has already entered the error state,
** do not attempt the rollback.
*/
static void pagerUnlockAndRollback(Pager *p){
if( p->errCode==SQLITE_OK && p->state>=PAGER_RESERVED ){
sqlite3BeginBenignMalloc();
sqlite3PagerRollback(p);
sqlite3EndBenignMalloc();
}
pager_unlock(p);
}
/*
** This routine ends a transaction. A transaction is ended by either
** a COMMIT or a ROLLBACK.
**
** When this routine is called, the pager has the journal file open and
** a RESERVED or EXCLUSIVE lock on the database. This routine will release
** the database lock and acquires a SHARED lock in its place if that is
** the appropriate thing to do. Release locks usually is appropriate,
** unless we are in exclusive access mode or unless this is a
** COMMIT AND BEGIN or ROLLBACK AND BEGIN operation.
**
** The journal file is either deleted or truncated.
**
** TODO: Consider keeping the journal file open for temporary databases.
** This might give a performance improvement on windows where opening
** a file is an expensive operation.
*/
static int pager_end_transaction(Pager *pPager, int hasMaster){
int rc = SQLITE_OK;
int rc2 = SQLITE_OK;
if( pPager->state<PAGER_RESERVED ){
return SQLITE_OK;
}
sqlite3PagerStmtCommit(pPager);
if( pPager->stmtOpen && !pPager->exclusiveMode ){
sqlite3OsClose(pPager->stfd);
pPager->stmtOpen = 0;
}
if( pPager->journalOpen ){
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
int isMemoryJournal = sqlite3IsMemJournal(pPager->jfd);
sqlite3OsClose(pPager->jfd);
pPager->journalOpen = 0;
if( !isMemoryJournal ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
}else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE
&& (rc = sqlite3OsTruncate(pPager->jfd, 0))==SQLITE_OK ){
pPager->journalOff = 0;
pPager->journalStarted = 0;
}else if( pPager->exclusiveMode
|| pPager->journalMode==PAGER_JOURNALMODE_PERSIST
){
rc = zeroJournalHdr(pPager, hasMaster);
pager_error(pPager, rc);
pPager->journalOff = 0;
pPager->journalStarted = 0;
}else{
assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE || rc );
sqlite3OsClose(pPager->jfd);
pPager->journalOpen = 0;
if( rc==SQLITE_OK && !pPager->tempFile ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
}
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
sqlite3BitvecDestroy(pPager->pAlwaysRollback);
pPager->pAlwaysRollback = 0;
#ifdef SQLITE_CHECK_PAGES
sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
#endif
sqlite3PcacheCleanAll(pPager->pPCache);
pPager->dirtyCache = 0;
pPager->nRec = 0;
}else{
assert( pPager->pInJournal==0 );
}
if( !pPager->exclusiveMode ){
rc2 = osUnlock(pPager->fd, SHARED_LOCK);
pPager->state = PAGER_SHARED;
}else if( pPager->state==PAGER_SYNCED ){
pPager->state = PAGER_EXCLUSIVE;
}
pPager->origDbSize = 0;
pPager->setMaster = 0;
pPager->needSync = 0;
/* lruListSetFirstSynced(pPager); */
if( !MEMDB ){
pPager->dbSizeValid = 0;
}
pPager->dbModified = 0;
return (rc==SQLITE_OK?rc2:rc);
}
/*
** Compute and return a checksum for the page of data.
**
** This is not a real checksum. It is really just the sum of the
** random initial value and the page number. We experimented with
** a checksum of the entire data, but that was found to be too slow.
**
** Note that the page number is stored at the beginning of data and
** the checksum is stored at the end. This is important. If journal
** corruption occurs due to a power failure, the most likely scenario
** is that one end or the other of the record will be changed. It is
** much less likely that the two ends of the journal record will be
** correct and the middle be corrupt. Thus, this "checksum" scheme,
** though fast and simple, catches the mostly likely kind of corruption.
**
** FIX ME: Consider adding every 200th (or so) byte of the data to the
** checksum. That way if a single page spans 3 or more disk sectors and
** only the middle sector is corrupt, we will still have a reasonable
** chance of failing the checksum and thus detecting the problem.
*/
static u32 pager_cksum(Pager *pPager, const u8 *aData){
u32 cksum = pPager->cksumInit;
int i = pPager->pageSize-200;
while( i>0 ){
cksum += aData[i];
i -= 200;
}
return cksum;
}
/*
** Read a single page from the journal file opened on file descriptor
** jfd. Playback this one page.
**
** The isMainJrnl flag is true if this is the main rollback journal and
** false for the statement journal. The main rollback journal uses
** checksums - the statement journal does not.
*/
static int pager_playback_one_page(
Pager *pPager, /* The pager being played back */
sqlite3_file *jfd, /* The file that is the journal being rolled back */
i64 offset, /* Offset of the page within the journal */
int isMainJrnl /* True for main rollback journal. False for Stmt jrnl */
){
int rc;
PgHdr *pPg; /* An existing page in the cache */
Pgno pgno; /* The page number of a page in journal */
u32 cksum; /* Checksum used for sanity checking */
u8 *aData = (u8 *)pPager->pTmpSpace; /* Temp storage for a page */
/* isMainJrnl should be true for the main journal and false for
** statement journals. Verify that this is always the case
*/
assert( jfd == (isMainJrnl ? pPager->jfd : pPager->stfd) );
assert( aData );
rc = read32bits(jfd, offset, &pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(jfd, aData, pPager->pageSize, offset+4);
if( rc!=SQLITE_OK ) return rc;
pPager->journalOff += pPager->pageSize + 4;
/* Sanity checking on the page. This is more important that I originally
** thought. If a power failure occurs while the journal is being written,
** it could cause invalid data to be written into the journal. We need to
** detect this invalid data (with high probability) and ignore it.
*/
if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
return SQLITE_DONE;
}
if( pgno>(unsigned)pPager->dbSize ){
return SQLITE_OK;
}
if( isMainJrnl ){
rc = read32bits(jfd, offset+pPager->pageSize+4, &cksum);
if( rc ) return rc;
pPager->journalOff += 4;
if( pager_cksum(pPager, aData)!=cksum ){
return SQLITE_DONE;
}
}
assert( pPager->state==PAGER_RESERVED || pPager->state>=PAGER_EXCLUSIVE );
/* If the pager is in RESERVED state, then there must be a copy of this
** page in the pager cache. In this case just update the pager cache,
** not the database file. The page is left marked dirty in this case.
**
** An exception to the above rule: If the database is in no-sync mode
** and a page is moved during an incremental vacuum then the page may
** not be in the pager cache. Later: if a malloc() or IO error occurs
** during a Movepage() call, then the page may not be in the cache
** either. So the condition described in the above paragraph is not
** assert()able.
**
** If in EXCLUSIVE state, then we update the pager cache if it exists
** and the main file. The page is then marked not dirty.
**
** Ticket #1171: The statement journal might contain page content that is
** different from the page content at the start of the transaction.
** This occurs when a page is changed prior to the start of a statement
** then changed again within the statement. When rolling back such a
** statement we must not write to the original database unless we know
** for certain that original page contents are synced into the main rollback
** journal. Otherwise, a power loss might leave modified data in the
** database file without an entry in the rollback journal that can
** restore the database to its original form. Two conditions must be
** met before writing to the database files. (1) the database must be
** locked. (2) we know that the original page content is fully synced
** in the main journal either because the page is not in cache or else
** the page is marked as needSync==0.
**
** 2008-04-14: When attempting to vacuum a corrupt database file, it
** is possible to fail a statement on a database that does not yet exist.
** Do not attempt to write if database file has never been opened.
*/
pPg = pager_lookup(pPager, pgno);
PAGERTRACE4("PLAYBACK %d page %d hash(%08x)\n",
PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, aData));
if( (pPager->state>=PAGER_EXCLUSIVE)
&& (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC))
&& (pPager->fd->pMethods)
){
i64 ofst = (pgno-1)*(i64)pPager->pageSize;
rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize, ofst);
}
if( pPg ){
/* No page should ever be explicitly rolled back that is in use, except
** for page 1 which is held in use in order to keep the lock on the
** database active. However such a page may be rolled back as a result
** of an internal error resulting in an automatic call to
** sqlite3PagerRollback().
*/
void *pData;
pData = pPg->pData;
memcpy(pData, aData, pPager->pageSize);
if( pPager->xReiniter ){
pPager->xReiniter(pPg);
}
if( isMainJrnl ){
sqlite3PcacheMakeClean(pPg);
}
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
/* If this was page 1, then restore the value of Pager.dbFileVers.
** Do this before any decoding. */
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
}
/* Decode the page just read from disk */
CODEC1(pPager, pData, pPg->pgno, 3);
sqlite3PcacheRelease(pPg);
}
return rc;
}
/*
** Parameter zMaster is the name of a master journal file. A single journal
** file that referred to the master journal file has just been rolled back.
** This routine checks if it is possible to delete the master journal file,
** and does so if it is.
**
** Argument zMaster may point to Pager.pTmpSpace. So that buffer is not
** available for use within this function.
**
**
** The master journal file contains the names of all child journals.
** To tell if a master journal can be deleted, check to each of the
** children. If all children are either missing or do not refer to
** a different master journal, then this master journal can be deleted.
*/
static int pager_delmaster(Pager *pPager, const char *zMaster){
sqlite3_vfs *pVfs = pPager->pVfs;
int rc;
int master_open = 0;
sqlite3_file *pMaster;
sqlite3_file *pJournal;
char *zMasterJournal = 0; /* Contents of master journal file */
i64 nMasterJournal; /* Size of master journal file */
/* Open the master journal file exclusively in case some other process
** is running this routine also. Not that it makes too much difference.
*/
pMaster = (sqlite3_file *)sqlite3Malloc(pVfs->szOsFile * 2);
pJournal = (sqlite3_file *)(((u8 *)pMaster) + pVfs->szOsFile);
if( !pMaster ){
rc = SQLITE_NOMEM;
}else{
int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MASTER_JOURNAL);
rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0);
}
if( rc!=SQLITE_OK ) goto delmaster_out;
master_open = 1;
rc = sqlite3OsFileSize(pMaster, &nMasterJournal);
if( rc!=SQLITE_OK ) goto delmaster_out;
if( nMasterJournal>0 ){
char *zJournal;
char *zMasterPtr = 0;
int nMasterPtr = pPager->pVfs->mxPathname+1;
/* Load the entire master journal file into space obtained from
** sqlite3_malloc() and pointed to by zMasterJournal.
*/
zMasterJournal = (char *)sqlite3Malloc(nMasterJournal + nMasterPtr);
if( !zMasterJournal ){
rc = SQLITE_NOMEM;
goto delmaster_out;
}
zMasterPtr = &zMasterJournal[nMasterJournal];
rc = sqlite3OsRead(pMaster, zMasterJournal, nMasterJournal, 0);
if( rc!=SQLITE_OK ) goto delmaster_out;
zJournal = zMasterJournal;
while( (zJournal-zMasterJournal)<nMasterJournal ){
int exists;
rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
if( exists ){
/* One of the journals pointed to by the master journal exists.
** Open it and check if it points at the master journal. If
** so, return without deleting the master journal file.
*/
int c;
int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL);
rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
rc = readMasterJournal(pJournal, zMasterPtr, nMasterPtr);
sqlite3OsClose(pJournal);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
c = zMasterPtr[0]!=0 && strcmp(zMasterPtr, zMaster)==0;
if( c ){
/* We have a match. Do not delete the master journal file. */
goto delmaster_out;
}
}
zJournal += (strlen(zJournal)+1);
}
}
rc = sqlite3OsDelete(pVfs, zMaster, 0);
delmaster_out:
if( zMasterJournal ){
sqlite3_free(zMasterJournal);
}
if( master_open ){
sqlite3OsClose(pMaster);
}
sqlite3_free(pMaster);
return rc;
}
static void pager_truncate_cache(Pager *pPager);
/*
** Truncate the main file of the given pager to the number of pages
** indicated. Also truncate the cached representation of the file.
**
** Might might be the case that the file on disk is smaller than nPage.
** This can happen, for example, if we are in the middle of a transaction
** which has extended the file size and the new pages are still all held
** in cache, then an INSERT or UPDATE does a statement rollback. Some
** operating system implementations can get confused if you try to
** truncate a file to some size that is larger than it currently is,
** so detect this case and write a single zero byte to the end of the new
** file instead.
*/
static int pager_truncate(Pager *pPager, Pgno nPage){
int rc = SQLITE_OK;
if( pPager->state>=PAGER_EXCLUSIVE && pPager->fd->pMethods ){
i64 currentSize, newSize;
rc = sqlite3OsFileSize(pPager->fd, &currentSize);
newSize = pPager->pageSize*(i64)nPage;
if( rc==SQLITE_OK && currentSize!=newSize ){
if( currentSize>newSize ){
rc = sqlite3OsTruncate(pPager->fd, newSize);
}else{
rc = sqlite3OsWrite(pPager->fd, "", 1, newSize-1);
}
}
}
if( rc==SQLITE_OK ){
pPager->dbSize = nPage;
pager_truncate_cache(pPager);
}
return rc;
}
/*
** Set the sectorSize for the given pager.
**
** The sector size is at least as big as the sector size reported
** by sqlite3OsSectorSize(). The minimum sector size is 512.
*/
static void setSectorSize(Pager *pPager){
assert(pPager->fd->pMethods||pPager->tempFile);
if( !pPager->tempFile ){
/* Sector size doesn't matter for temporary files. Also, the file
** may not have been opened yet, in whcih case the OsSectorSize()
** call will segfault.
*/
pPager->sectorSize = sqlite3OsSectorSize(pPager->fd);
}
if( pPager->sectorSize<512 ){
pPager->sectorSize = 512;
}
}
/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.
**
** The journal file format is as follows:
**
** (1) 8 byte prefix. A copy of aJournalMagic[].
** (2) 4 byte big-endian integer which is the number of valid page records
** in the journal. If this value is 0xffffffff, then compute the
** number of page records from the journal size.
** (3) 4 byte big-endian integer which is the initial value for the
** sanity checksum.
** (4) 4 byte integer which is the number of pages to truncate the
** database to during a rollback.
** (5) 4 byte big-endian integer which is the sector size. The header
** is this many bytes in size.
** (6) 4 byte big-endian integer which is the page case.
** (7) 4 byte integer which is the number of bytes in the master journal
** name. The value may be zero (indicate that there is no master
** journal.)
** (8) N bytes of the master journal name. The name will be nul-terminated
** and might be shorter than the value read from (5). If the first byte
** of the name is \000 then there is no master journal. The master
** journal name is stored in UTF-8.
** (9) Zero or more pages instances, each as follows:
** + 4 byte page number.
** + pPager->pageSize bytes of data.
** + 4 byte checksum
**
** When we speak of the journal header, we mean the first 8 items above.
** Each entry in the journal is an instance of the 9th item.
**
** Call the value from the second bullet "nRec". nRec is the number of
** valid page entries in the journal. In most cases, you can compute the
** value of nRec from the size of the journal file. But if a power
** failure occurred while the journal was being written, it could be the
** case that the size of the journal file had already been increased but
** the extra entries had not yet made it safely to disk. In such a case,
** the value of nRec computed from the file size would be too large. For
** that reason, we always use the nRec value in the header.
**
** If the nRec value is 0xffffffff it means that nRec should be computed
** from the file size. This value is used when the user selects the
** no-sync option for the journal. A power failure could lead to corruption
** in this case. But for things like temporary table (which will be
** deleted when the power is restored) we don't care.
**
** If the file opened as the journal file is not a well-formed
** journal file then all pages up to the first corrupted page are rolled
** back (or no pages if the journal header is corrupted). The journal file
** is then deleted and SQLITE_OK returned, just as if no corruption had
** been encountered.
**
** If an I/O or malloc() error occurs, the journal-file is not deleted
** and an error code is returned.
*/
static int pager_playback(Pager *pPager, int isHot){
sqlite3_vfs *pVfs = pPager->pVfs;
i64 szJ; /* Size of the journal file in bytes */
u32 nRec; /* Number of Records in the journal */
u32 u; /* Unsigned loop counter */
Pgno mxPg = 0; /* Size of the original file in pages */
int rc; /* Result code of a subroutine */
int res = 1; /* Value returned by sqlite3OsAccess() */
char *zMaster = 0; /* Name of master journal file if any */
/* Figure out how many records are in the journal. Abort early if
** the journal is empty.
*/
assert( pPager->journalOpen );
rc = sqlite3OsFileSize(pPager->jfd, &szJ);
if( rc!=SQLITE_OK || szJ==0 ){
goto end_playback;
}
/* Read the master journal name from the journal, if it is present.
** If a master journal file name is specified, but the file is not
** present on disk, then the journal is not hot and does not need to be
** played back.
*/
zMaster = pPager->pTmpSpace;
rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
if( rc==SQLITE_OK && zMaster[0] ){
rc = sqlite3OsAccess(pVfs, zMaster, SQLITE_ACCESS_EXISTS, &res);
}
zMaster = 0;
if( rc!=SQLITE_OK || !res ){
goto end_playback;
}
pPager->journalOff = 0;
/* This loop terminates either when the readJournalHdr() call returns
** SQLITE_DONE or an IO error occurs. */
while( 1 ){
/* Read the next journal header from the journal file. If there are
** not enough bytes left in the journal file for a complete header, or
** it is corrupted, then a process must of failed while writing it.
** This indicates nothing more needs to be rolled back.
*/
rc = readJournalHdr(pPager, szJ, &nRec, &mxPg);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
}
goto end_playback;
}
/* If nRec is 0xffffffff, then this journal was created by a process
** working in no-sync mode. This means that the rest of the journal
** file consists of pages, there are no more journal headers. Compute
** the value of nRec based on this assumption.
*/
if( nRec==0xffffffff ){
assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
nRec = (szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager);
}
/* If nRec is 0 and this rollback is of a transaction created by this
** process and if this is the final header in the journal, then it means
** that this part of the journal was being filled but has not yet been
** synced to disk. Compute the number of pages based on the remaining
** size of the file.
**
** The third term of the test was added to fix ticket #2565.
*/
if( nRec==0 && !isHot &&
pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
nRec = (szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager);
}
/* If this is the first header read from the journal, truncate the
** database file back to its original size.
*/
if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
rc = pager_truncate(pPager, mxPg);
if( rc!=SQLITE_OK ){
goto end_playback;
}
}
/* Copy original pages out of the journal and back into the database file.
*/
for(u=0; u<nRec; u++){
rc = pager_playback_one_page(pPager, pPager->jfd, pPager->journalOff, 1);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
pPager->journalOff = szJ;
break;
}else{
/* If we are unable to rollback, then the database is probably
** going to end up being corrupt. It is corrupt to us, anyhow.
** Perhaps the next process to come along can fix it....
*/
rc = SQLITE_CORRUPT_BKPT;
goto end_playback;
}
}
}
}
/*NOTREACHED*/
assert( 0 );
end_playback:
if( rc==SQLITE_OK ){
zMaster = pPager->pTmpSpace;
rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
}
if( rc==SQLITE_OK ){
rc = pager_end_transaction(pPager, zMaster[0]!='\0');
}
if( rc==SQLITE_OK && zMaster[0] && res ){
/* If there was a master journal and this routine will return success,
** see if it is possible to delete the master journal.
*/
rc = pager_delmaster(pPager, zMaster);
}
/* The Pager.sectorSize variable may have been updated while rolling
** back a journal created by a process with a different sector size
** value. Reset it to the correct value for this process.
*/
setSectorSize(pPager);
return rc;
}
/*
** Playback the statement journal.
**
** This is similar to playing back the transaction journal but with
** a few extra twists.
**
** (1) The number of pages in the database file at the start of
** the statement is stored in pPager->stmtSize, not in the
** journal file itself.
**
** (2) In addition to playing back the statement journal, also
** playback all pages of the transaction journal beginning
** at offset pPager->stmtJSize.
*/
static int pager_stmt_playback(Pager *pPager){
i64 szJ; /* Size of the full journal */
i64 hdrOff;
int nRec; /* Number of Records */
int i; /* Loop counter */
int rc;
szJ = pPager->journalOff;
/* Set hdrOff to be the offset just after the end of the last journal
** page written before the first journal-header for this statement
** transaction was written, or the end of the file if no journal
** header was written.
*/
hdrOff = pPager->stmtHdrOff;
assert( pPager->fullSync || !hdrOff );
if( !hdrOff ){
hdrOff = szJ;
}
/* Truncate the database back to its original size.
*/
rc = pager_truncate(pPager, pPager->stmtSize);
assert( pPager->state>=PAGER_SHARED );
/* Figure out how many records are in the statement journal.
*/
assert( pPager->stmtInUse && pPager->journalOpen );
nRec = pPager->stmtNRec;
/* Copy original pages out of the statement journal and back into the
** database file. Note that the statement journal omits checksums from
** each record since power-failure recovery is not important to statement
** journals.
*/
for(i=0; i<nRec; i++){
i64 offset = i*(4+pPager->pageSize);
rc = pager_playback_one_page(pPager, pPager->stfd, offset, 0);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK ) goto end_stmt_playback;
}
/* Now roll some pages back from the transaction journal. Pager.stmtJSize
** was the size of the journal file when this statement was started, so
** everything after that needs to be rolled back, either into the
** database, the memory cache, or both.
**
** If it is not zero, then Pager.stmtHdrOff is the offset to the start
** of the first journal header written during this statement transaction.
*/
pPager->journalOff = pPager->stmtJSize;
pPager->cksumInit = pPager->stmtCksum;
while( pPager->journalOff < hdrOff ){
rc = pager_playback_one_page(pPager, pPager->jfd, pPager->journalOff, 1);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK ) goto end_stmt_playback;
}
while( pPager->journalOff < szJ ){
u32 nJRec; /* Number of Journal Records */
u32 dummy;
rc = readJournalHdr(pPager, szJ, &nJRec, &dummy);
if( rc!=SQLITE_OK ){
assert( rc!=SQLITE_DONE );
goto end_stmt_playback;
}
if( nJRec==0 ){
nJRec = (szJ - pPager->journalOff) / (pPager->pageSize+8);
}
for(i=nJRec-1; i>=0 && pPager->journalOff < szJ; i--){
rc = pager_playback_one_page(pPager, pPager->jfd, pPager->journalOff, 1);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK ) goto end_stmt_playback;
}
}
pPager->journalOff = szJ;
end_stmt_playback:
if( rc==SQLITE_OK) {
pPager->journalOff = szJ;
/* pager_reload_cache(pPager); */
}
return rc;
}
/*
** Change the maximum number of in-memory pages that are allowed.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
}
/*
** Adjust the robustness of the database to damage due to OS crashes
** or power failures by changing the number of syncs()s when writing
** the rollback journal. There are three levels:
**
** OFF sqlite3OsSync() is never called. This is the default
** for temporary and transient files.
**
** NORMAL The journal is synced once before writes begin on the
** database. This is normally adequate protection, but
** it is theoretically possible, though very unlikely,
** that an inopertune power failure could leave the journal
** in a state which would cause damage to the database
** when it is rolled back.
**
** FULL The journal is synced twice before writes begin on the
** database (with some additional information - the nRec field
** of the journal header - being written in between the two
** syncs). If we assume that writing a
** single disk sector is atomic, then this mode provides
** assurance that the journal will not be corrupted to the
** point of causing damage to the database during rollback.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
void sqlite3PagerSetSafetyLevel(Pager *pPager, int level, int bFullFsync){
pPager->noSync = level==1 || pPager->tempFile;
pPager->fullSync = level==3 && !pPager->tempFile;
pPager->sync_flags = (bFullFsync?SQLITE_SYNC_FULL:SQLITE_SYNC_NORMAL);
if( pPager->noSync ) pPager->needSync = 0;
}
#endif
/*
** The following global variable is incremented whenever the library
** attempts to open a temporary file. This information is used for
** testing and analysis only.
*/
#ifdef SQLITE_TEST
int sqlite3_opentemp_count = 0;
#endif
/*
** Open a temporary file.
**
** Write the file descriptor into *fd. Return SQLITE_OK on success or some
** other error code if we fail. The OS will automatically delete the temporary
** file when it is closed.
*/
static int sqlite3PagerOpentemp(
Pager *pPager, /* The pager object */
sqlite3_file *pFile, /* Write the file descriptor here */
int vfsFlags /* Flags passed through to the VFS */
){
int rc;
#ifdef SQLITE_TEST
sqlite3_opentemp_count++; /* Used for testing and analysis only */
#endif
vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
assert( rc!=SQLITE_OK || pFile->pMethods );
return rc;
}
static int pagerStress(void *,PgHdr *);
/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist. The file is not locked until
** the first call to sqlite3PagerGet() and is only held open until the
** last page is released using sqlite3PagerUnref().
**
** If zFilename is NULL then a randomly-named temporary file is created
** and used as the file to be cached. The file will be deleted
** automatically when it is closed.
**
** If zFilename is ":memory:" then all information is held in cache.
** It is never written to disk. This can be used to implement an
** in-memory database.
*/
int sqlite3PagerOpen(
sqlite3_vfs *pVfs, /* The virtual file system to use */
Pager **ppPager, /* Return the Pager structure here */
const char *zFilename, /* Name of the database file to open */
int nExtra, /* Extra bytes append to each in-memory page */
int flags, /* flags controlling this file */
int vfsFlags /* flags passed through to sqlite3_vfs.xOpen() */
){
u8 *pPtr;
Pager *pPager = 0;
int rc = SQLITE_OK;
int i;
int tempFile = 0;
int memDb = 0;
int readOnly = 0;
int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
int journalFileSize;
int pcacheSize = sqlite3PcacheSize();
int szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;
char *zPathname = 0;
int nPathname = 0;
if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){
journalFileSize = sqlite3JournalSize(pVfs);
}else{
journalFileSize = sqlite3MemJournalSize();
}
/* The default return is a NULL pointer */
*ppPager = 0;
/* Compute and store the full pathname in an allocated buffer pointed
** to by zPathname, length nPathname. Or, if this is a temporary file,
** leave both nPathname and zPathname set to 0.
*/
if( zFilename && zFilename[0] ){
nPathname = pVfs->mxPathname+1;
zPathname = sqlite3Malloc(nPathname*2);
if( zPathname==0 ){
return SQLITE_NOMEM;
}
#ifndef SQLITE_OMIT_MEMORYDB
if( strcmp(zFilename,":memory:")==0 ){
memDb = 1;
zPathname[0] = 0;
}else
#endif
{
rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
}
if( rc!=SQLITE_OK ){
sqlite3_free(zPathname);
return rc;
}
nPathname = strlen(zPathname);
}
/* Allocate memory for the pager structure */
pPager = sqlite3MallocZero(
sizeof(*pPager) + /* Pager structure */
pcacheSize + /* PCache object */
journalFileSize + /* The journal file structure */
pVfs->szOsFile + /* The main db file */
journalFileSize * 2 + /* The two journal files */
3*nPathname + 40 /* zFilename, zDirectory, zJournal */
);
if( !pPager ){
sqlite3_free(zPathname);
return SQLITE_NOMEM;
}
pPager->pPCache = (PCache *)&pPager[1];
pPtr = ((u8 *)&pPager[1]) + pcacheSize;
pPager->vfsFlags = vfsFlags;
pPager->fd = (sqlite3_file*)&pPtr[pVfs->szOsFile*0];
pPager->stfd = (sqlite3_file*)&pPtr[pVfs->szOsFile];
pPager->jfd = (sqlite3_file*)&pPtr[pVfs->szOsFile+journalFileSize];
pPager->zFilename = (char*)&pPtr[pVfs->szOsFile+2*journalFileSize];
pPager->zDirectory = &pPager->zFilename[nPathname+1];
pPager->zJournal = &pPager->zDirectory[nPathname+1];
pPager->pVfs = pVfs;
if( zPathname ){
memcpy(pPager->zFilename, zPathname, nPathname+1);
sqlite3_free(zPathname);
}
/* Open the pager file.
*/
if( zFilename && zFilename[0] && !memDb ){
if( nPathname>(pVfs->mxPathname - (int)sizeof("-journal")) ){
rc = SQLITE_CANTOPEN;
}else{
int fout = 0;
rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd,
pPager->vfsFlags, &fout);
readOnly = (fout&SQLITE_OPEN_READONLY);
/* If the file was successfully opened for read/write access,
** choose a default page size in case we have to create the
** database file. The default page size is the maximum of:
**
** + SQLITE_DEFAULT_PAGE_SIZE,
** + The value returned by sqlite3OsSectorSize()
** + The largest page size that can be written atomically.
*/
if( rc==SQLITE_OK && !readOnly ){
int iSectorSize = sqlite3OsSectorSize(pPager->fd);
if( szPageDflt<iSectorSize ){
szPageDflt = iSectorSize;
}
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
{
int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
int ii;
assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ) szPageDflt = ii;
}
}
#endif
if( szPageDflt>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
}
}
}
}else{
/* If a temporary file is requested, it is not opened immediately.
** In this case we accept the default page size and delay actually
** opening the file until the first call to OsWrite().
**
** This branch is also run for an in-memory database. An in-memory
** database is the same as a temp-file that is never written out to
** disk and uses an in-memory rollback journal.
*/
tempFile = 1;
pPager->state = PAGER_EXCLUSIVE;
}
if( pPager && rc==SQLITE_OK ){
pPager->pTmpSpace = sqlite3PageMalloc(szPageDflt);
}
/* If an error occured in either of the blocks above.
** Free the Pager structure and close the file.
** Since the pager is not allocated there is no need to set
** any Pager.errMask variables.
*/
if( !pPager || !pPager->pTmpSpace ){
sqlite3OsClose(pPager->fd);
sqlite3_free(pPager);
return ((rc==SQLITE_OK)?SQLITE_NOMEM:rc);
}
nExtra = FORCE_ALIGNMENT(nExtra);
sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
!memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
PAGERTRACE3("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename);
IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
/* Fill in Pager.zDirectory[] */
memcpy(pPager->zDirectory, pPager->zFilename, nPathname+1);
for(i=strlen(pPager->zDirectory); i>0 && pPager->zDirectory[i-1]!='/'; i--){}
if( i>0 ) pPager->zDirectory[i-1] = 0;
/* Fill in Pager.zJournal[] */
if( zPathname ){
memcpy(pPager->zJournal, pPager->zFilename, nPathname);
memcpy(&pPager->zJournal[nPathname], "-journal", 9);
}else{
pPager->zJournal = 0;
}
/* pPager->journalOpen = 0; */
pPager->useJournal = useJournal;
pPager->noReadlock = noReadlock && readOnly;
/* pPager->stmtOpen = 0; */
/* pPager->stmtInUse = 0; */
/* pPager->nRef = 0; */
pPager->dbSizeValid = memDb;
pPager->pageSize = szPageDflt;
/* pPager->stmtSize = 0; */
/* pPager->stmtJSize = 0; */
/* pPager->nPage = 0; */
pPager->mxPage = 100;
pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
/* pPager->state = PAGER_UNLOCK; */
assert( pPager->state == (tempFile ? PAGER_EXCLUSIVE : PAGER_UNLOCK) );
/* pPager->errMask = 0; */
pPager->tempFile = tempFile;
assert( tempFile==PAGER_LOCKINGMODE_NORMAL
|| tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
pPager->exclusiveMode = tempFile;
pPager->memDb = memDb;
pPager->readOnly = readOnly;
/* pPager->needSync = 0; */
pPager->noSync = pPager->tempFile || !useJournal;
pPager->fullSync = (pPager->noSync?0:1);
pPager->sync_flags = SQLITE_SYNC_NORMAL;
/* pPager->pFirst = 0; */
/* pPager->pFirstSynced = 0; */
/* pPager->pLast = 0; */
pPager->nExtra = nExtra;
pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
assert(pPager->fd->pMethods||tempFile);
setSectorSize(pPager);
if( memDb ){
pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
}
/* pPager->xBusyHandler = 0; */
/* pPager->pBusyHandlerArg = 0; */
/* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
*ppPager = pPager;
return SQLITE_OK;
}
/*
** Set the busy handler function.
*/
void sqlite3PagerSetBusyhandler(
Pager *pPager,
int (*xBusyHandler)(void *),
void *pBusyHandlerArg
){
pPager->xBusyHandler = xBusyHandler;
pPager->pBusyHandlerArg = pBusyHandlerArg;
}
/*
** Set the reinitializer for this pager. If not NULL, the reinitializer
** is called when the content of a page in cache is restored to its original
** value as a result of a rollback. The callback gives higher-level code
** an opportunity to restore the EXTRA section to agree with the restored
** page data.
*/
void sqlite3PagerSetReiniter(Pager *pPager, void (*xReinit)(DbPage*)){
pPager->xReiniter = xReinit;
}
/*
** Set the page size to *pPageSize. If the suggest new page size is
** inappropriate, then an alternative page size is set to that
** value before returning.
*/
int sqlite3PagerSetPagesize(Pager *pPager, u16 *pPageSize){
int rc = pPager->errCode;
if( rc==SQLITE_OK ){
u16 pageSize = *pPageSize;
assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
if( pageSize && pageSize!=pPager->pageSize
&& (pPager->memDb==0 || pPager->dbSize==0)
&& sqlite3PcacheRefCount(pPager->pPCache)==0
){
char *pNew = (char *)sqlite3PageMalloc(pageSize);
if( !pNew ){
rc = SQLITE_NOMEM;
}else{
pager_reset(pPager);
pPager->pageSize = pageSize;
if( !pPager->memDb ) setSectorSize(pPager);
sqlite3PageFree(pPager->pTmpSpace);
pPager->pTmpSpace = pNew;
sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
}
}
*pPageSize = pPager->pageSize;
}
return rc;
}
/*
** Return a pointer to the "temporary page" buffer held internally
** by the pager. This is a buffer that is big enough to hold the
** entire content of a database page. This buffer is used internally
** during rollback and will be overwritten whenever a rollback
** occurs. But other modules are free to use it too, as long as
** no rollbacks are happening.
*/
void *sqlite3PagerTempSpace(Pager *pPager){
return pPager->pTmpSpace;
}
/*
** Attempt to set the maximum database page count if mxPage is positive.
** Make no changes if mxPage is zero or negative. And never reduce the
** maximum page count below the current size of the database.
**
** Regardless of mxPage, return the current maximum page count.
*/
int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
if( mxPage>0 ){
pPager->mxPgno = mxPage;
}
sqlite3PagerPagecount(pPager, 0);
return pPager->mxPgno;
}
/*
** The following set of routines are used to disable the simulated
** I/O error mechanism. These routines are used to avoid simulated
** errors in places where we do not care about errors.
**
** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
** and generate no code.
*/
#ifdef SQLITE_TEST
extern int sqlite3_io_error_pending;
extern int sqlite3_io_error_hit;
static int saved_cnt;
void disable_simulated_io_errors(void){
saved_cnt = sqlite3_io_error_pending;
sqlite3_io_error_pending = -1;
}
void enable_simulated_io_errors(void){
sqlite3_io_error_pending = saved_cnt;
}
#else
# define disable_simulated_io_errors()
# define enable_simulated_io_errors()
#endif
/*
** Read the first N bytes from the beginning of the file into memory
** that pDest points to.
**
** No error checking is done. The rational for this is that this function
** may be called even if the file does not exist or contain a header. In
** these cases sqlite3OsRead() will return an error, to which the correct
** response is to zero the memory at pDest and continue. A real IO error
** will presumably recur and be picked up later (Todo: Think about this).
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
int rc = SQLITE_OK;
memset(pDest, 0, N);
assert(pPager->fd->pMethods||pPager->tempFile);
if( pPager->fd->pMethods ){
IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
}
return rc;
}
/*
** Return the total number of pages in the disk file associated with
** pPager.
**
** If the PENDING_BYTE lies on the page directly after the end of the
** file, then consider this page part of the file too. For example, if
** PENDING_BYTE is byte 4096 (the first byte of page 5) and the size of the
** file is 4096 bytes, 5 is returned instead of 4.
*/
int sqlite3PagerPagecount(Pager *pPager, int *pnPage){
i64 n = 0;
int rc;
assert( pPager!=0 );
if( pPager->errCode ){
rc = pPager->errCode;
return rc;
}
if( pPager->dbSizeValid ){
n = pPager->dbSize;
} else {
assert(pPager->fd->pMethods||pPager->tempFile);
if( (pPager->fd->pMethods)
&& (rc = sqlite3OsFileSize(pPager->fd, &n))!=SQLITE_OK ){
pager_error(pPager, rc);
return rc;
}
if( n>0 && n<pPager->pageSize ){
n = 1;
}else{
n /= pPager->pageSize;
}
if( pPager->state!=PAGER_UNLOCK ){
pPager->dbSize = n;
pPager->dbSizeValid = 1;
}
}
if( n==(PENDING_BYTE/pPager->pageSize) ){
n++;
}
if( n>pPager->mxPgno ){
pPager->mxPgno = n;
}
if( pnPage ){
*pnPage = n;
}
return SQLITE_OK;
}
/*
** Forward declaration
*/
static int syncJournal(Pager*);
/*
** This routine is used to truncate the cache when a database
** is truncated. Drop from the cache all pages whose pgno is
** larger than pPager->dbSize and is unreferenced.
**
** Referenced pages larger than pPager->dbSize are zeroed.
**
** Actually, at the point this routine is called, it would be
** an error to have a referenced page. But rather than delete
** that page and guarantee a subsequent segfault, it seems better
** to zero it and hope that we error out sanely.
*/
static void pager_truncate_cache(Pager *pPager){
sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
}
/*
** Try to obtain a lock on a file. Invoke the busy callback if the lock
** is currently not available. Repeat until the busy callback returns
** false or until the lock succeeds.
**
** Return SQLITE_OK on success and an error code if we cannot obtain
** the lock.
*/
static int pager_wait_on_lock(Pager *pPager, int locktype){
int rc;
/* The OS lock values must be the same as the Pager lock values */
assert( PAGER_SHARED==SHARED_LOCK );
assert( PAGER_RESERVED==RESERVED_LOCK );
assert( PAGER_EXCLUSIVE==EXCLUSIVE_LOCK );
/* If the file is currently unlocked then the size must be unknown */
assert( pPager->state>=PAGER_SHARED || pPager->dbSizeValid==0 );
if( pPager->state>=locktype ){
rc = SQLITE_OK;
}else{
do {
rc = sqlite3OsLock(pPager->fd, locktype);
}while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
if( rc==SQLITE_OK ){
pPager->state = locktype;
IOTRACE(("LOCK %p %d\n", pPager, locktype))
}
}
return rc;
}
/*
** Truncate the file to the number of pages specified.
*/
int sqlite3PagerTruncate(Pager *pPager, Pgno nPage){
int rc = SQLITE_OK;
assert( pPager->state>=PAGER_SHARED );
sqlite3PagerPagecount(pPager, 0);
if( pPager->errCode ){
rc = pPager->errCode;
}else if( nPage<pPager->dbSize ){
rc = syncJournal(pPager);
if( rc==SQLITE_OK ){
/* Get an exclusive lock on the database before truncating. */
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
if( rc==SQLITE_OK ){
rc = pager_truncate(pPager, nPage);
}
}
return rc;
}
/*
** Shutdown the page cache. Free all memory and close all files.
**
** If a transaction was in progress when this routine is called, that
** transaction is rolled back. All outstanding pages are invalidated
** and their memory is freed. Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
**
** This function always succeeds. If a transaction is active an attempt
** is made to roll it back. If an error occurs during the rollback
** a hot journal may be left in the filesystem but no error is returned
** to the caller.
*/
int sqlite3PagerClose(Pager *pPager){
disable_simulated_io_errors();
sqlite3BeginBenignMalloc();
pPager->errCode = 0;
pPager->exclusiveMode = 0;
pager_reset(pPager);
if( !MEMDB ){
pagerUnlockAndRollback(pPager);
}
enable_simulated_io_errors();
sqlite3EndBenignMalloc();
PAGERTRACE2("CLOSE %d\n", PAGERID(pPager));
IOTRACE(("CLOSE %p\n", pPager))
if( pPager->journalOpen ){
sqlite3OsClose(pPager->jfd);
}
sqlite3BitvecDestroy(pPager->pInJournal);
sqlite3BitvecDestroy(pPager->pAlwaysRollback);
if( pPager->stmtOpen ){
sqlite3OsClose(pPager->stfd);
}
sqlite3OsClose(pPager->fd);
/* Temp files are automatically deleted by the OS
** if( pPager->tempFile ){
** sqlite3OsDelete(pPager->zFilename);
** }
*/
sqlite3PageFree(pPager->pTmpSpace);
sqlite3PcacheClose(pPager->pPCache);
sqlite3_free(pPager);
return SQLITE_OK;
}
#if !defined(NDEBUG) || defined(SQLITE_TEST)
/*
** Return the page number for the given page data.
*/
Pgno sqlite3PagerPagenumber(DbPage *p){
return p->pgno;
}
#endif
/*
** Increment the reference count for a page. The input pointer is
** a reference to the page data.
*/
int sqlite3PagerRef(DbPage *pPg){
sqlite3PcacheRef(pPg);
return SQLITE_OK;
}
/*
** Sync the journal. In other words, make sure all the pages that have
** been written to the journal have actually reached the surface of the
** disk. It is not safe to modify the original database file until after
** the journal has been synced. If the original database is modified before
** the journal is synced and a power failure occurs, the unsynced journal
** data would be lost and we would be unable to completely rollback the
** database changes. Database corruption would occur.
**
** This routine also updates the nRec field in the header of the journal.
** (See comments on the pager_playback() routine for additional information.)
** If the sync mode is FULL, two syncs will occur. First the whole journal
** is synced, then the nRec field is updated, then a second sync occurs.
**
** For temporary databases, we do not care if we are able to rollback
** after a power failure, so no sync occurs.
**
** If the IOCAP_SEQUENTIAL flag is set for the persistent media on which
** the database is stored, then OsSync() is never called on the journal
** file. In this case all that is required is to update the nRec field in
** the journal header.
**
** This routine clears the needSync field of every page current held in
** memory.
*/
static int syncJournal(Pager *pPager){
int rc = SQLITE_OK;
/* Sync the journal before modifying the main database
** (assuming there is a journal and it needs to be synced.)
*/
if( pPager->needSync ){
assert( !pPager->tempFile );
if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
assert( pPager->journalOpen );
if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
/* Write the nRec value into the journal file header. If in
** full-synchronous mode, sync the journal first. This ensures that
** all data has really hit the disk before nRec is updated to mark
** it as a candidate for rollback.
**
** This is not required if the persistent media supports the
** SAFE_APPEND property. Because in this case it is not possible
** for garbage data to be appended to the file, the nRec field
** is populated with 0xFFFFFFFF when the journal header is written
** and never needs to be updated.
*/
i64 jrnlOff;
if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags);
if( rc!=0 ) return rc;
}
jrnlOff = pPager->journalHdr + sizeof(aJournalMagic);
IOTRACE(("JHDR %p %lld %d\n", pPager, jrnlOff, 4));
rc = write32bits(pPager->jfd, jrnlOff, pPager->nRec);
if( rc ) return rc;
}
if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags|
(pPager->sync_flags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
);
if( rc!=0 ) return rc;
}
pPager->journalStarted = 1;
}
pPager->needSync = 0;
/* Erase the needSync flag from every page.
*/
sqlite3PcacheClearSyncFlags(pPager->pPCache);
}
return rc;
}
/*
** Given a list of pages (connected by the PgHdr.pDirty pointer) write
** every one of those pages out to the database file. No calls are made
** to the page-cache to mark the pages as clean. It is the responsibility
** of the caller to use PcacheCleanAll() or PcacheMakeClean() to mark
** the pages as clean.
*/
static int pager_write_pagelist(PgHdr *pList){
Pager *pPager;
int rc;
if( pList==0 ) return SQLITE_OK;
pPager = pList->pPager;
/* At this point there may be either a RESERVED or EXCLUSIVE lock on the
** database file. If there is already an EXCLUSIVE lock, the following
** calls to sqlite3OsLock() are no-ops.
**
** Moving the lock from RESERVED to EXCLUSIVE actually involves going
** through an intermediate state PENDING. A PENDING lock prevents new
** readers from attaching to the database but is unsufficient for us to
** write. The idea of a PENDING lock is to prevent new readers from
** coming in while we wait for existing readers to clear.
**
** While the pager is in the RESERVED state, the original database file
** is unchanged and we can rollback without having to playback the
** journal into the original database file. Once we transition to
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
return rc;
}
while( pList ){
/* If the file has not yet been opened, open it now. */
if( !pPager->fd->pMethods ){
assert(pPager->tempFile);
rc = sqlite3PagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
if( rc ) return rc;
}
/* If there are dirty pages in the page cache with page numbers greater
** than Pager.dbSize, this means sqlite3PagerTruncate() was called to
** make the file smaller (presumably by auto-vacuum code). Do not write
** any such pages to the file.
*/
if( pList->pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
i64 offset = (pList->pgno-1)*(i64)pPager->pageSize;
char *pData = CODEC2(pPager, pList->pData, pList->pgno, 6);
PAGERTRACE4("STORE %d page %d hash(%08x)\n",
PAGERID(pPager), pList->pgno, pager_pagehash(pList));
IOTRACE(("PGOUT %p %d\n", pPager, pList->pgno));
rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
PAGER_INCR(sqlite3_pager_writedb_count);
PAGER_INCR(pPager->nWrite);
if( pList->pgno==1 ){
memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
}
}
#ifndef NDEBUG
else{
PAGERTRACE3("NOSTORE %d page %d\n", PAGERID(pPager), pList->pgno);
}
#endif
if( rc ) return rc;
#ifdef SQLITE_CHECK_PAGES
pList->pageHash = pager_pagehash(pList);
#endif
pList = pList->pDirty;
}
return SQLITE_OK;
}
/*
** This function is called by the pcache layer when it has reached some
** soft memory limit. The argument is a pointer to a purgeable Pager
** object. This function attempts to make a single dirty page that has no
** outstanding references (if one exists) clean so that it can be recycled
** by the pcache layer.
*/
static int pagerStress(void *p, PgHdr *pPg){
Pager *pPager = (Pager *)p;
int rc = SQLITE_OK;
if( pPager->doNotSync ){
return SQLITE_OK;
}
assert( pPg->flags&PGHDR_DIRTY );
if( pPager->errCode==SQLITE_OK ){
if( pPg->flags&PGHDR_NEED_SYNC ){
rc = syncJournal(pPager);
if( rc==SQLITE_OK && pPager->fullSync &&
!(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
!(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
){
pPager->nRec = 0;
rc = writeJournalHdr(pPager);
}
}
if( rc==SQLITE_OK ){
pPg->pDirty = 0;
rc = pager_write_pagelist(pPg);
}
if( rc!=SQLITE_OK ){
pager_error(pPager, rc);
}
}
if( rc==SQLITE_OK ){
sqlite3PcacheMakeClean(pPg);
}
return rc;
}
/*
** Return 1 if there is a hot journal on the given pager.
** A hot journal is one that needs to be played back.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
** database with the same name. Just delete the journal.
**
** Return negative if unable to determine the status of the journal.
**
** This routine does not open the journal file to examine its
** content. Hence, the journal might contain the name of a master
** journal file that has been deleted, and hence not be hot. Or
** the header of the journal might be zeroed out. This routine
** does not discover these cases of a non-hot journal - if the
** journal file exists and is not empty this routine assumes it
** is hot. The pager_playback() routine will discover that the
** journal file is not really hot and will no-op.
*/
static int hasHotJournal(Pager *pPager, int *pExists){
sqlite3_vfs *pVfs = pPager->pVfs;
int rc = SQLITE_OK;
int exists;
int locked;
assert( pPager!=0 );
assert( pPager->useJournal );
assert( pPager->fd->pMethods );
*pExists = 0;
rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
if( rc==SQLITE_OK && exists ){
rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
}
if( rc==SQLITE_OK && exists && !locked ){
int nPage;
rc = sqlite3PagerPagecount(pPager, &nPage);
if( rc==SQLITE_OK ){
if( nPage==0 ){
sqlite3OsDelete(pVfs, pPager->zJournal, 0);
}else{
*pExists = 1;
}
}
}
return rc;
}
/*
** Read the content of page pPg out of the database file.
*/
static int readDbPage(Pager *pPager, PgHdr *pPg, Pgno pgno){
int rc;
i64 offset;
assert( MEMDB==0 );
assert(pPager->fd->pMethods||pPager->tempFile);
if( !pPager->fd->pMethods ){
return SQLITE_IOERR_SHORT_READ;
}
offset = (pgno-1)*(i64)pPager->pageSize;
rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, offset);
PAGER_INCR(sqlite3_pager_readdb_count);
PAGER_INCR(pPager->nRead);
IOTRACE(("PGIN %p %d\n", pPager, pgno));
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &((u8*)pPg->pData)[24],
sizeof(pPager->dbFileVers));
}
CODEC1(pPager, pPg->pData, pPg->pgno, 3);
PAGERTRACE4("FETCH %d page %d hash(%08x)\n",
PAGERID(pPager), pPg->pgno, pager_pagehash(pPg));
return rc;
}
/*
** This function is called to obtain the shared lock required before
** data may be read from the pager cache. If the shared lock has already
** been obtained, this function is a no-op.
**
** Immediately after obtaining the shared lock (if required), this function
** checks for a hot-journal file. If one is found, an emergency rollback
** is performed immediately.
*/
static int pagerSharedLock(Pager *pPager){
int rc = SQLITE_OK;
int isErrorReset = 0;
/* If this database is opened for exclusive access, has no outstanding
** page references and is in an error-state, now is the chance to clear
** the error. Discard the contents of the pager-cache and treat any
** open journal file as a hot-journal.
*/
if( !MEMDB && pPager->exclusiveMode
&& sqlite3PcacheRefCount(pPager->pPCache)==0 && pPager->errCode
){
if( pPager->journalOpen ){
isErrorReset = 1;
}
pPager->errCode = SQLITE_OK;
pager_reset(pPager);
}
/* If the pager is still in an error state, do not proceed. The error
** state will be cleared at some point in the future when all page
** references are dropped and the cache can be discarded.
*/
if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
return pPager->errCode;
}
if( pPager->state==PAGER_UNLOCK || isErrorReset ){
sqlite3_vfs *pVfs = pPager->pVfs;
int isHotJournal;
assert( !MEMDB );
assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
if( !pPager->noReadlock ){
rc = pager_wait_on_lock(pPager, SHARED_LOCK);
if( rc!=SQLITE_OK ){
assert( pPager->state==PAGER_UNLOCK );
return pager_error(pPager, rc);
}
assert( pPager->state>=SHARED_LOCK );
}
/* If a journal file exists, and there is no RESERVED lock on the
** database file, then it either needs to be played back or deleted.
*/
if( !isErrorReset ){
rc = hasHotJournal(pPager, &isHotJournal);
if( rc!=SQLITE_OK ){
goto failed;
}
}
if( isErrorReset || isHotJournal ){
/* Get an EXCLUSIVE lock on the database file. At this point it is
** important that a RESERVED lock is not obtained on the way to the
** EXCLUSIVE lock. If it were, another process might open the
** database file, detect the RESERVED lock, and conclude that the
** database is safe to read while this process is still rolling it
** back.
**
** Because the intermediate RESERVED lock is not requested, the
** second process will get to this point in the code and fail to
** obtain its own EXCLUSIVE lock on the database file.
*/
if( pPager->state<EXCLUSIVE_LOCK ){
rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
rc = pager_error(pPager, rc);
goto failed;
}
pPager->state = PAGER_EXCLUSIVE;
}
/* Open the journal for read/write access. This is because in
** exclusive-access mode the file descriptor will be kept open and
** possibly used for a transaction later on. On some systems, the
** OsTruncate() call used in exclusive-access mode also requires
** a read/write file handle.
*/
if( !isErrorReset && pPager->journalOpen==0 ){
int res;
rc = sqlite3OsAccess(pVfs,pPager->zJournal,SQLITE_ACCESS_EXISTS,&res);
if( rc==SQLITE_OK ){
if( res ){
int fout = 0;
int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
assert( !pPager->tempFile );
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
assert( rc!=SQLITE_OK || pPager->jfd->pMethods );
if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
rc = SQLITE_CANTOPEN;
sqlite3OsClose(pPager->jfd);
}
}else{
/* If the journal does not exist, that means some other process
** has already rolled it back */
rc = SQLITE_BUSY;
}
}
}
if( rc!=SQLITE_OK ){
goto failed;
}
pPager->journalOpen = 1;
pPager->journalStarted = 0;
pPager->journalOff = 0;
pPager->setMaster = 0;
pPager->journalHdr = 0;
/* Playback and delete the journal. Drop the database write
** lock and reacquire the read lock.
*/
rc = pager_playback(pPager, 1);
if( rc!=SQLITE_OK ){
rc = pager_error(pPager, rc);
goto failed;
}
assert(pPager->state==PAGER_SHARED ||
(pPager->exclusiveMode && pPager->state>PAGER_SHARED)
);
}
if( sqlite3PcachePagecount(pPager->pPCache)>0 ){
/* The shared-lock has just been acquired on the database file
** and there are already pages in the cache (from a previous
** read or write transaction). Check to see if the database
** has been modified. If the database has changed, flush the
** cache.
**
** Database changes is detected by looking at 15 bytes beginning
** at offset 24 into the file. The first 4 of these 16 bytes are
** a 32-bit counter that is incremented with each change. The
** other bytes change randomly with each file change when
** a codec is in use.
**
** There is a vanishingly small chance that a change will not be
** detected. The chance of an undetected change is so small that
** it can be neglected.
*/
char dbFileVers[sizeof(pPager->dbFileVers)];
sqlite3PagerPagecount(pPager, 0);
if( pPager->errCode ){
rc = pPager->errCode;
goto failed;
}
assert( pPager->dbSizeValid );
if( pPager->dbSize>0 ){
IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
if( rc!=SQLITE_OK ){
goto failed;
}
}else{
memset(dbFileVers, 0, sizeof(dbFileVers));
}
if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
pager_reset(pPager);
}
}
assert( pPager->exclusiveMode || pPager->state<=PAGER_SHARED );
if( pPager->state==PAGER_UNLOCK ){
pPager->state = PAGER_SHARED;
}
}
failed:
if( rc!=SQLITE_OK ){
/* pager_unlock() is a no-op for exclusive mode and in-memory databases. */
pager_unlock(pPager);
}
return rc;
}
/*
** Make sure we have the content for a page. If the page was
** previously acquired with noContent==1, then the content was
** just initialized to zeros instead of being read from disk.
** But now we need the real data off of disk. So make sure we
** have it. Read it in if we do not have it already.
*/
static int pager_get_content(PgHdr *pPg){
if( pPg->flags&PGHDR_NEED_READ ){
int rc = readDbPage(pPg->pPager, pPg, pPg->pgno);
if( rc==SQLITE_OK ){
pPg->flags &= ~PGHDR_NEED_READ;
}else{
return rc;
}
}
return SQLITE_OK;
}
/*
** If the reference count has reached zero, and the pager is not in the
** middle of a write transaction or opened in exclusive mode, unlock it.
*/
static void pagerUnlockIfUnused(Pager *pPager){
if( (sqlite3PcacheRefCount(pPager->pPCache)==0)
&& (!pPager->exclusiveMode || pPager->journalOff>0)
){
pagerUnlockAndRollback(pPager);
}
}
/*
** Drop a page from the cache using sqlite3PcacheDrop().
**
** If this means there are now no pages with references to them, a rollback
** occurs and the lock on the database is removed.
*/
static void pagerDropPage(DbPage *pPg){
Pager *pPager = pPg->pPager;
sqlite3PcacheDrop(pPg);
pagerUnlockIfUnused(pPager);
}
/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired.
** This read lock is dropped when the last page is released.
**
** This routine works for any page number greater than 0. If the database
** file is smaller than the requested page, then no actual disk
** read occurs and the memory image of the page is initialized to
** all zeros. The extra data appended to a page is always initialized
** to zeros the first time a page is loaded into memory.
**
** The acquisition might fail for several reasons. In all cases,
** an appropriate error code is returned and *ppPage is set to NULL.
**
** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt
** to find a page in the in-memory cache first. If the page is not already
** in memory, this routine goes to disk to read it in whereas Lookup()
** just returns 0. This routine acquires a read-lock the first time it
** has to go to disk, and could also playback an old journal if necessary.
** Since Lookup() never goes to disk, it never has to deal with locks
** or journal files.
**
** If noContent is false, the page contents are actually read from disk.
** If noContent is true, it means that we do not care about the contents
** of the page at this time, so do not do a disk read. Just fill in the
** page content with zeros. But mark the fact that we have not read the
** content by setting the PgHdr.needRead flag. Later on, if
** sqlite3PagerWrite() is called on this page or if this routine is
** called again with noContent==0, that means that the content is needed
** and the disk read should occur at that point.
*/
int sqlite3PagerAcquire(
Pager *pPager, /* The pager open on the database file */
Pgno pgno, /* Page number to fetch */
DbPage **ppPage, /* Write a pointer to the page here */
int noContent /* Do not bother reading content from disk if true */
){
PgHdr *pPg = 0;
int rc;
assert( pPager->state==PAGER_UNLOCK
|| sqlite3PcacheRefCount(pPager->pPCache)>0
|| pgno==1
);
/* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
** number greater than this, or zero, is requested.
*/
if( pgno>PAGER_MAX_PGNO || pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
return SQLITE_CORRUPT_BKPT;
}
/* Make sure we have not hit any critical errors.
*/
assert( pPager!=0 );
*ppPage = 0;
/* If this is the first page accessed, then get a SHARED lock
** on the database file. pagerSharedLock() is a no-op if
** a database lock is already held.
*/
rc = pagerSharedLock(pPager);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pPager->state!=PAGER_UNLOCK );
rc = sqlite3PcacheFetch(pPager->pPCache, pgno, 1, &pPg);
if( rc!=SQLITE_OK ){
return rc;
}
if( pPg->pPager==0 ){
/* The pager cache has created a new page. Its content needs to
** be initialized.
*/
int nMax;
PAGER_INCR(pPager->nMiss);
pPg->pPager = pPager;
memset(pPg->pExtra, 0, pPager->nExtra);
rc = sqlite3PagerPagecount(pPager, &nMax);
if( rc!=SQLITE_OK ){
sqlite3PagerUnref(pPg);
return rc;
}
if( nMax<(int)pgno || MEMDB || noContent ){
if( pgno>pPager->mxPgno ){
sqlite3PagerUnref(pPg);
return SQLITE_FULL;
}
memset(pPg->pData, 0, pPager->pageSize);
if( noContent ){
pPg->flags |= PGHDR_NEED_READ;
}
IOTRACE(("ZERO %p %d\n", pPager, pgno));
}else{
rc = readDbPage(pPager, pPg, pgno);
if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
/* sqlite3PagerUnref(pPg); */
pagerDropPage(pPg);
return rc;
}
}
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
}else{
/* The requested page is in the page cache. */
assert(sqlite3PcacheRefCount(pPager->pPCache)>0 || pgno==1);
PAGER_INCR(pPager->nHit);
if( !noContent ){
rc = pager_get_content(pPg);
if( rc ){
sqlite3PagerUnref(pPg);
return rc;
}
}
}
*ppPage = pPg;
return SQLITE_OK;
}
/*
** Acquire a page if it is already in the in-memory cache. Do
** not read the page from disk. Return a pointer to the page,
** or 0 if the page is not in cache.
**
** See also sqlite3PagerGet(). The difference between this routine
** and sqlite3PagerGet() is that _get() will go to the disk and read
** in the page if the page is not already in cache. This routine
** returns NULL if the page is not in cache or if a disk I/O error
** has ever happened.
*/
DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
PgHdr *pPg = 0;
assert( pPager!=0 );
assert( pgno!=0 );
if( (pPager->state!=PAGER_UNLOCK)
&& (pPager->errCode==SQLITE_OK || pPager->errCode==SQLITE_FULL)
){
sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &pPg);
}
return pPg;
}
/*
** Release a page.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list. When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
int sqlite3PagerUnref(DbPage *pPg){
if( pPg ){
Pager *pPager = pPg->pPager;
sqlite3PcacheRelease(pPg);
pagerUnlockIfUnused(pPager);
}
return SQLITE_OK;
}
/*
** Create a journal file for pPager. There should already be a RESERVED
** or EXCLUSIVE lock on the database file when this routine is called.
**
** Return SQLITE_OK if everything. Return an error code and release the
** write lock if anything goes wrong.
*/
static int pager_open_journal(Pager *pPager){
sqlite3_vfs *pVfs = pPager->pVfs;
int flags = (SQLITE_OPEN_READWRITE|SQLITE_OPEN_EXCLUSIVE|SQLITE_OPEN_CREATE);
int rc;
assert( pPager->state>=PAGER_RESERVED );
assert( pPager->useJournal );
assert( pPager->pInJournal==0 );
sqlite3PagerPagecount(pPager, 0);
pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
if( pPager->pInJournal==0 ){
rc = SQLITE_NOMEM;
goto failed_to_open_journal;
}
if( pPager->journalOpen==0 ){
if( pPager->tempFile ){
flags |= (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL);
}else{
flags |= (SQLITE_OPEN_MAIN_JOURNAL);
}
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
sqlite3MemJournalOpen(pPager->jfd);
rc = SQLITE_OK;
}else{
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
rc = sqlite3JournalOpen(
pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
);
#else
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
#endif
}
assert( rc!=SQLITE_OK || pPager->jfd->pMethods );
pPager->journalOff = 0;
pPager->setMaster = 0;
pPager->journalHdr = 0;
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM ){
sqlite3OsDelete(pVfs, pPager->zJournal, 0);
}
goto failed_to_open_journal;
}
}
pPager->journalOpen = 1;
pPager->journalStarted = 0;
pPager->needSync = 0;
pPager->nRec = 0;
if( pPager->errCode ){
rc = pPager->errCode;
goto failed_to_open_journal;
}
pPager->origDbSize = pPager->dbSize;
rc = writeJournalHdr(pPager);
if( pPager->stmtAutoopen && rc==SQLITE_OK ){
rc = sqlite3PagerStmtBegin(pPager);
}
if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM && rc!=SQLITE_IOERR_NOMEM ){
rc = pager_end_transaction(pPager, 0);
if( rc==SQLITE_OK ){
rc = SQLITE_FULL;
}
}
return rc;
failed_to_open_journal:
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
return rc;
}
/*
** Acquire a write-lock on the database. The lock is removed when
** the any of the following happen:
**
** * sqlite3PagerCommitPhaseTwo() is called.
** * sqlite3PagerRollback() is called.
** * sqlite3PagerClose() is called.
** * sqlite3PagerUnref() is called to on every outstanding page.
**
** The first parameter to this routine is a pointer to any open page of the
** database file. Nothing changes about the page - it is used merely to
** acquire a pointer to the Pager structure and as proof that there is
** already a read-lock on the database.
**
** The second parameter indicates how much space in bytes to reserve for a
** master journal file-name at the start of the journal when it is created.
**
** A journal file is opened if this is not a temporary file. For temporary
** files, the opening of the journal file is deferred until there is an
** actual need to write to the journal.
**
** If the database is already reserved for writing, this routine is a no-op.
**
** If exFlag is true, go ahead and get an EXCLUSIVE lock on the file
** immediately instead of waiting until we try to flush the cache. The
** exFlag is ignored if a transaction is already active.
*/
int sqlite3PagerBegin(DbPage *pPg, int exFlag){
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
assert( pPg->nRef>0 );
assert( pPager->state!=PAGER_UNLOCK );
if( pPager->state==PAGER_SHARED ){
assert( pPager->pInJournal==0 );
assert( !MEMDB );
rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
if( rc==SQLITE_OK ){
pPager->state = PAGER_RESERVED;
if( exFlag ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
if( rc!=SQLITE_OK ){
return rc;
}
pPager->dirtyCache = 0;
PAGERTRACE2("TRANSACTION %d\n", PAGERID(pPager));
if( pPager->useJournal && !pPager->tempFile
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
rc = pager_open_journal(pPager);
}
}else if( pPager->journalOpen && pPager->journalOff==0 ){
/* This happens when the pager was in exclusive-access mode the last
** time a (read or write) transaction was successfully concluded
** by this connection. Instead of deleting the journal file it was
** kept open and either was truncated to 0 bytes or its header was
** overwritten with zeros.
*/
assert( pPager->nRec==0 );
assert( pPager->origDbSize==0 );
assert( pPager->pInJournal==0 );
sqlite3PagerPagecount(pPager, 0);
pPager->pInJournal = sqlite3BitvecCreate( pPager->dbSize );
if( !pPager->pInJournal ){
rc = SQLITE_NOMEM;
}else{
pPager->origDbSize = pPager->dbSize;
rc = writeJournalHdr(pPager);
}
}
assert( !pPager->journalOpen || pPager->journalOff>0 || rc!=SQLITE_OK );
return rc;
}
/*
** Mark a data page as writeable. The page is written into the journal
** if it is not there already. This routine must be called before making
** changes to a page.
**
** The first time this routine is called, the pager creates a new
** journal and acquires a RESERVED lock on the database. If the RESERVED
** lock could not be acquired, this routine returns SQLITE_BUSY. The
** calling routine must check for that return value and be careful not to
** change any page data until this routine returns SQLITE_OK.
**
** If the journal file could not be written because the disk is full,
** then this routine returns SQLITE_FULL and does an immediate rollback.
** All subsequent write attempts also return SQLITE_FULL until there
** is a call to sqlite3PagerCommit() or sqlite3PagerRollback() to
** reset.
*/
static int pager_write(PgHdr *pPg){
void *pData = pPg->pData;
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
/* Check for errors
*/
if( pPager->errCode ){
return pPager->errCode;
}
if( pPager->readOnly ){
return SQLITE_PERM;
}
assert( !pPager->setMaster );
CHECK_PAGE(pPg);
/* If this page was previously acquired with noContent==1, that means
** we didn't really read in the content of the page. This can happen
** (for example) when the page is being moved to the freelist. But
** now we are (perhaps) moving the page off of the freelist for
** reuse and we need to know its original content so that content
** can be stored in the rollback journal. So do the read at this
** time.
*/
rc = pager_get_content(pPg);
if( rc ){
return rc;
}
/* Mark the page as dirty. If the page has already been written
** to the journal then we can return right away.
*/
sqlite3PcacheMakeDirty(pPg);
if( pageInJournal(pPg) && (pageInStatement(pPg) || pPager->stmtInUse==0) ){
pPager->dirtyCache = 1;
pPager->dbModified = 1;
}else{
/* If we get this far, it means that the page needs to be
** written to the transaction journal or the ckeckpoint journal
** or both.
**
** First check to see that the transaction journal exists and
** create it if it does not.
*/
assert( pPager->state!=PAGER_UNLOCK );
rc = sqlite3PagerBegin(pPg, 0);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pPager->state>=PAGER_RESERVED );
if( !pPager->journalOpen && pPager->useJournal
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
rc = pager_open_journal(pPager);
if( rc!=SQLITE_OK ) return rc;
}
pPager->dirtyCache = 1;
pPager->dbModified = 1;
/* The transaction journal now exists and we have a RESERVED or an
** EXCLUSIVE lock on the main database file. Write the current page to
** the transaction journal if it is not there already.
*/
if( !pageInJournal(pPg) && pPager->journalOpen ){
if( pPg->pgno<=pPager->origDbSize ){
u32 cksum;
char *pData2;
/* We should never write to the journal file the page that
** contains the database locks. The following assert verifies
** that we do not. */
assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
cksum = pager_cksum(pPager, (u8*)pData2);
rc = write32bits(pPager->jfd, pPager->journalOff, pPg->pgno);
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize,
pPager->journalOff + 4);
pPager->journalOff += pPager->pageSize+4;
}
if( rc==SQLITE_OK ){
rc = write32bits(pPager->jfd, pPager->journalOff, cksum);
pPager->journalOff += 4;
}
IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno,
pPager->journalOff, pPager->pageSize));
PAGER_INCR(sqlite3_pager_writej_count);
PAGERTRACE5("JOURNAL %d page %d needSync=%d hash(%08x)\n",
PAGERID(pPager), pPg->pgno,
((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg));
/* An error has occured writing to the journal file. The
** transaction will be rolled back by the layer above.
*/
if( rc!=SQLITE_OK ){
return rc;
}
pPager->nRec++;
assert( pPager->pInJournal!=0 );
sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
if( !pPager->noSync ){
pPg->flags |= PGHDR_NEED_SYNC;
}
if( pPager->stmtInUse ){
sqlite3BitvecSet(pPager->pInStmt, pPg->pgno);
}
}else{
if( !pPager->journalStarted && !pPager->noSync ){
pPg->flags |= PGHDR_NEED_SYNC;
}
PAGERTRACE4("APPEND %d page %d needSync=%d\n",
PAGERID(pPager), pPg->pgno,
((pPg->flags&PGHDR_NEED_SYNC)?1:0));
}
if( pPg->flags&PGHDR_NEED_SYNC ){
pPager->needSync = 1;
}
}
/* If the statement journal is open and the page is not in it,
** then write the current page to the statement journal. Note that
** the statement journal format differs from the standard journal format
** in that it omits the checksums and the header.
*/
if( pPager->stmtInUse
&& !pageInStatement(pPg)
&& pPg->pgno<=pPager->stmtSize
){
i64 offset = pPager->stmtNRec*(4+pPager->pageSize);
char *pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
assert( pageInJournal(pPg) || pPg->pgno>pPager->origDbSize );
rc = write32bits(pPager->stfd, offset, pPg->pgno);
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->stfd, pData2, pPager->pageSize, offset+4);
}
PAGERTRACE3("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);
if( rc!=SQLITE_OK ){
return rc;
}
pPager->stmtNRec++;
assert( pPager->pInStmt!=0 );
sqlite3BitvecSet(pPager->pInStmt, pPg->pgno);
}
}
/* Update the database size and return.
*/
assert( pPager->state>=PAGER_SHARED );
if( pPager->dbSize<pPg->pgno ){
pPager->dbSize = pPg->pgno;
if( pPager->dbSize==(PAGER_MJ_PGNO(pPager)-1) ){
pPager->dbSize++;
}
}
return rc;
}
/*
** This function is used to mark a data-page as writable. It uses
** pager_write() to open a journal file (if it is not already open)
** and write the page *pData to the journal.
**
** The difference between this function and pager_write() is that this
** function also deals with the special case where 2 or more pages
** fit on a single disk sector. In this case all co-resident pages
** must have been written to the journal file before returning.
*/
int sqlite3PagerWrite(DbPage *pDbPage){
int rc = SQLITE_OK;
PgHdr *pPg = pDbPage;
Pager *pPager = pPg->pPager;
Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
if( nPagePerSector>1 ){
Pgno nPageCount; /* Total number of pages in database file */
Pgno pg1; /* First page of the sector pPg is located on. */
int nPage; /* Number of pages starting at pg1 to journal */
int ii;
int needSync = 0;
/* Set the doNotSync flag to 1. This is because we cannot allow a journal
** header to be written between the pages journaled by this function.
*/
assert( !MEMDB );
assert( pPager->doNotSync==0 );
pPager->doNotSync = 1;
/* This trick assumes that both the page-size and sector-size are
** an integer power of 2. It sets variable pg1 to the identifier
** of the first page of the sector pPg is located on.
*/
pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
sqlite3PagerPagecount(pPager, (int *)&nPageCount);
if( pPg->pgno>nPageCount ){
nPage = (pPg->pgno - pg1)+1;
}else if( (pg1+nPagePerSector-1)>nPageCount ){
nPage = nPageCount+1-pg1;
}else{
nPage = nPagePerSector;
}
assert(nPage>0);
assert(pg1<=pPg->pgno);
assert((pg1+nPage)>pPg->pgno);
for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
Pgno pg = pg1+ii;
PgHdr *pPage;
if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
if( pg!=PAGER_MJ_PGNO(pPager) ){
rc = sqlite3PagerGet(pPager, pg, &pPage);
if( rc==SQLITE_OK ){
rc = pager_write(pPage);
if( pPage->flags&PGHDR_NEED_SYNC ){
needSync = 1;
}
sqlite3PagerUnref(pPage);
}
}
}else if( (pPage = pager_lookup(pPager, pg))!=0 ){
if( pPage->flags&PGHDR_NEED_SYNC ){
needSync = 1;
}
sqlite3PagerUnref(pPage);
}
}
/* If the PgHdr.needSync flag is set for any of the nPage pages
** starting at pg1, then it needs to be set for all of them. Because
** writing to any of these nPage pages may damage the others, the
** journal file must contain sync()ed copies of all of them
** before any of them can be written out to the database file.
*/
if( needSync ){
assert( !MEMDB && pPager->noSync==0 );
for(ii=0; ii<nPage && needSync; ii++){
PgHdr *pPage = pager_lookup(pPager, pg1+ii);
if( pPage ) pPage->flags |= PGHDR_NEED_SYNC;
sqlite3PagerUnref(pPage);
}
assert(pPager->needSync);
}
assert( pPager->doNotSync==1 );
pPager->doNotSync = 0;
}else{
rc = pager_write(pDbPage);
}
return rc;
}
/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3PagerWrite(). In other words, return TRUE if it is ok
** to change the content of the page.
*/
#ifndef NDEBUG
int sqlite3PagerIswriteable(DbPage *pPg){
return pPg->flags&PGHDR_DIRTY;
}
#endif
/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page pPg back to the disk, even though
** that page might be marked as dirty. This happens, for example, when
** the page has been added as a leaf of the freelist and so its
** content no longer matters.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused. The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization, together with the
** sqlite3PagerDontRollback() below, more than double the speed
** of large INSERT operations and quadruple the speed of large DELETEs.
**
** When this routine is called, set the alwaysRollback flag to true.
** Subsequent calls to sqlite3PagerDontRollback() for the same page
** will thereafter be ignored. This is necessary to avoid a problem
** where a page with data is added to the freelist during one part of
** a transaction then removed from the freelist during a later part
** of the same transaction and reused for some other purpose. When it
** is first added to the freelist, this routine is called. When reused,
** the sqlite3PagerDontRollback() routine is called. But because the
** page contains critical data, we still need to be sure it gets
** rolled back in spite of the sqlite3PagerDontRollback() call.
*/
int sqlite3PagerDontWrite(DbPage *pDbPage){
PgHdr *pPg = pDbPage;
Pager *pPager = pPg->pPager;
int rc;
if( pPg->pgno>pPager->origDbSize ){
return SQLITE_OK;
}
if( pPager->pAlwaysRollback==0 ){
assert( pPager->pInJournal );
pPager->pAlwaysRollback = sqlite3BitvecCreate(pPager->origDbSize);
if( !pPager->pAlwaysRollback ){
return SQLITE_NOMEM;
}
}
rc = sqlite3BitvecSet(pPager->pAlwaysRollback, pPg->pgno);
if( rc==SQLITE_OK && (pPg->flags&PGHDR_DIRTY) && !pPager->stmtInUse ){
assert( pPager->state>=PAGER_SHARED );
if( pPager->dbSize==pPg->pgno && pPager->origDbSize<pPager->dbSize ){
/* If this pages is the last page in the file and the file has grown
** during the current transaction, then do NOT mark the page as clean.
** When the database file grows, we must make sure that the last page
** gets written at least once so that the disk file will be the correct
** size. If you do not write this page and the size of the file
** on the disk ends up being too small, that can lead to database
** corruption during the next transaction.
*/
}else{
PAGERTRACE3("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager));
IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
pPg->flags |= PGHDR_DONT_WRITE;
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
}
}
return rc;
}
/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page. This
** means that the pager does not have to record the given page in the
** rollback journal.
**
** If we have not yet actually read the content of this page (if
** the PgHdr.needRead flag is set) then this routine acts as a promise
** that we will never need to read the page content in the future.
** so the needRead flag can be cleared at this point.
*/
void sqlite3PagerDontRollback(DbPage *pPg){
Pager *pPager = pPg->pPager;
assert( pPager->state>=PAGER_RESERVED );
/* If the journal file is not open, or DontWrite() has been called on
** this page (DontWrite() sets the alwaysRollback flag), then this
** function is a no-op.
*/
if( pPager->journalOpen==0
|| sqlite3BitvecTest(pPager->pAlwaysRollback, pPg->pgno)
|| pPg->pgno>pPager->origDbSize
){
return;
}
#ifdef SQLITE_SECURE_DELETE
if( sqlite3BitvecTest(pPager->pInJournal, pPg->pgno)!=0
|| pPg->pgno>pPager->origDbSize ){
return;
}
#endif
/* If SECURE_DELETE is disabled, then there is no way that this
** routine can be called on a page for which sqlite3PagerDontWrite()
** has not been previously called during the same transaction.
** And if DontWrite() has previously been called, the following
** conditions must be met.
**
** (Later:) Not true. If the database is corrupted by having duplicate
** pages on the freelist (ex: corrupt9.test) then the following is not
** necessarily true:
*/
/* assert( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ); */
assert( pPager->pInJournal!=0 );
sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
pPg->flags &= ~PGHDR_NEED_READ;
if( pPager->stmtInUse ){
assert( pPager->stmtSize >= pPager->origDbSize );
sqlite3BitvecSet(pPager->pInStmt, pPg->pgno);
}
PAGERTRACE3("DONT_ROLLBACK page %d of %d\n", pPg->pgno, PAGERID(pPager));
IOTRACE(("GARBAGE %p %d\n", pPager, pPg->pgno))
}
/*
** This routine is called to increment the database file change-counter,
** stored at byte 24 of the pager file.
*/
static int pager_incr_changecounter(Pager *pPager, int isDirect){
PgHdr *pPgHdr;
u32 change_counter;
int rc = SQLITE_OK;
#ifndef SQLITE_ENABLE_ATOMIC_WRITE
assert( isDirect==0 ); /* isDirect is only true for atomic writes */
#endif
if( !pPager->changeCountDone ){
/* Open page 1 of the file for writing. */
rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
if( rc!=SQLITE_OK ) return rc;
if( !isDirect ){
rc = sqlite3PagerWrite(pPgHdr);
if( rc!=SQLITE_OK ){
sqlite3PagerUnref(pPgHdr);
return rc;
}
}
/* Increment the value just read and write it back to byte 24. */
change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers);
change_counter++;
put32bits(((char*)pPgHdr->pData)+24, change_counter);
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
if( isDirect && pPager->fd->pMethods ){
const void *zBuf = pPgHdr->pData;
rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
}
#endif
/* Release the page reference. */
sqlite3PagerUnref(pPgHdr);
pPager->changeCountDone = 1;
}
return rc;
}
/*
** Sync the pager file to disk.
*/
int sqlite3PagerSync(Pager *pPager){
int rc;
if( MEMDB ){
rc = SQLITE_OK;
}else{
rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
}
return rc;
}
/*
** Sync the database file for the pager pPager. zMaster points to the name
** of a master journal file that should be written into the individual
** journal file. zMaster may be NULL, which is interpreted as no master
** journal (a single database transaction).
**
** This routine ensures that the journal is synced, all dirty pages written
** to the database file and the database file synced. The only thing that
** remains to commit the transaction is to delete the journal file (or
** master journal file if specified).
**
** Note that if zMaster==NULL, this does not overwrite a previous value
** passed to an sqlite3PagerCommitPhaseOne() call.
**
** If parameter nTrunc is non-zero, then the pager file is truncated to
** nTrunc pages (this is used by auto-vacuum databases).
**
** If the final parameter - noSync - is true, then the database file itself
** is not synced. The caller must call sqlite3PagerSync() directly to
** sync the database file before calling CommitPhaseTwo() to delete the
** journal file in this case.
*/
int sqlite3PagerCommitPhaseOne(
Pager *pPager,
const char *zMaster,
Pgno nTrunc,
int noSync
){
int rc = SQLITE_OK;
if( pPager->errCode ){
return pPager->errCode;
}
/* If no changes have been made, we can leave the transaction early.
*/
if( pPager->dbModified==0 &&
(pPager->journalMode!=PAGER_JOURNALMODE_DELETE ||
pPager->exclusiveMode!=0) ){
assert( pPager->dirtyCache==0 || pPager->journalOpen==0 );
return SQLITE_OK;
}
PAGERTRACE4("DATABASE SYNC: File=%s zMaster=%s nTrunc=%d\n",
pPager->zFilename, zMaster, nTrunc);
/* If this is an in-memory db, or no pages have been written to, or this
** function has already been called, it is a no-op.
*/
if( pPager->state!=PAGER_SYNCED && !MEMDB && pPager->dirtyCache ){
PgHdr *pPg;
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
/* The atomic-write optimization can be used if all of the
** following are true:
**
** + The file-system supports the atomic-write property for
** blocks of size page-size, and
** + This commit is not part of a multi-file transaction, and
** + Exactly one page has been modified and store in the journal file.
**
** If the optimization can be used, then the journal file will never
** be created for this transaction.
*/
int useAtomicWrite;
pPg = sqlite3PcacheDirtyList(pPager->pPCache);
useAtomicWrite = (
!zMaster &&
pPager->journalOpen &&
pPager->journalOff==jrnlBufferSize(pPager) &&
nTrunc==0 &&
(pPg==0 || pPg->pDirty==0)
);
assert( pPager->journalOpen || pPager->journalMode==PAGER_JOURNALMODE_OFF );
if( useAtomicWrite ){
/* Update the nRec field in the journal file. */
int offset = pPager->journalHdr + sizeof(aJournalMagic);
assert(pPager->nRec==1);
rc = write32bits(pPager->jfd, offset, pPager->nRec);
/* Update the db file change counter. The following call will modify
** the in-memory representation of page 1 to include the updated
** change counter and then write page 1 directly to the database
** file. Because of the atomic-write property of the host file-system,
** this is safe.
*/
if( rc==SQLITE_OK ){
rc = pager_incr_changecounter(pPager, 1);
}
}else{
rc = sqlite3JournalCreate(pPager->jfd);
}
if( !useAtomicWrite && rc==SQLITE_OK )
#endif
/* If a master journal file name has already been written to the
** journal file, then no sync is required. This happens when it is
** written, then the process fails to upgrade from a RESERVED to an
** EXCLUSIVE lock. The next time the process tries to commit the
** transaction the m-j name will have already been written.
*/
if( !pPager->setMaster ){
rc = pager_incr_changecounter(pPager, 0);
if( rc!=SQLITE_OK ) goto sync_exit;
if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
#ifndef SQLITE_OMIT_AUTOVACUUM
if( nTrunc!=0 ){
/* If this transaction has made the database smaller, then all pages
** being discarded by the truncation must be written to the journal
** file.
*/
Pgno i;
Pgno iSkip = PAGER_MJ_PGNO(pPager);
for( i=nTrunc+1; i<=pPager->origDbSize; i++ ){
if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
rc = sqlite3PagerGet(pPager, i, &pPg);
if( rc!=SQLITE_OK ) goto sync_exit;
rc = sqlite3PagerWrite(pPg);
sqlite3PagerUnref(pPg);
if( rc!=SQLITE_OK ) goto sync_exit;
}
}
}
#endif
rc = writeMasterJournal(pPager, zMaster);
if( rc!=SQLITE_OK ) goto sync_exit;
rc = syncJournal(pPager);
}
}
if( rc!=SQLITE_OK ) goto sync_exit;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( nTrunc!=0 ){
rc = sqlite3PagerTruncate(pPager, nTrunc);
if( rc!=SQLITE_OK ) goto sync_exit;
}
#endif
/* Write all dirty pages to the database file */
pPg = sqlite3PcacheDirtyList(pPager->pPCache);
rc = pager_write_pagelist(pPg);
if( rc!=SQLITE_OK ){
assert( rc!=SQLITE_IOERR_BLOCKED );
/* The error might have left the dirty list all fouled up here,
** but that does not matter because if the if the dirty list did
** get corrupted, then the transaction will roll back and
** discard the dirty list. There is an assert in
** pager_get_all_dirty_pages() that verifies that no attempt
** is made to use an invalid dirty list.
*/
goto sync_exit;
}
sqlite3PcacheCleanAll(pPager->pPCache);
/* Sync the database file. */
if( !pPager->noSync && !noSync ){
rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
}
IOTRACE(("DBSYNC %p\n", pPager))
pPager->state = PAGER_SYNCED;
}else if( MEMDB && nTrunc!=0 ){
rc = sqlite3PagerTruncate(pPager, nTrunc);
}
sync_exit:
if( rc==SQLITE_IOERR_BLOCKED ){
/* pager_incr_changecounter() may attempt to obtain an exclusive
* lock to spill the cache and return IOERR_BLOCKED. But since
* there is no chance the cache is inconsistent, it is
* better to return SQLITE_BUSY.
*/
rc = SQLITE_BUSY;
}
return rc;
}
/*
** Commit all changes to the database and release the write lock.
**
** If the commit fails for any reason, a rollback attempt is made
** and an error code is returned. If the commit worked, SQLITE_OK
** is returned.
*/
int sqlite3PagerCommitPhaseTwo(Pager *pPager){
int rc = SQLITE_OK;
if( pPager->errCode ){
return pPager->errCode;
}
if( pPager->state<PAGER_RESERVED ){
return SQLITE_ERROR;
}
if( pPager->dbModified==0 &&
(pPager->journalMode!=PAGER_JOURNALMODE_DELETE ||
pPager->exclusiveMode!=0) ){
assert( pPager->dirtyCache==0 || pPager->journalOpen==0 );
return SQLITE_OK;
}
PAGERTRACE2("COMMIT %d\n", PAGERID(pPager));
assert( pPager->state==PAGER_SYNCED || MEMDB || !pPager->dirtyCache );
rc = pager_end_transaction(pPager, pPager->setMaster);
rc = pager_error(pPager, rc);
return rc;
}
/*
** Rollback all changes. The database falls back to PAGER_SHARED mode.
** All in-memory cache pages revert to their original data contents.
** The journal is deleted.
**
** This routine cannot fail unless some other process is not following
** the correct locking protocol or unless some other
** process is writing trash into the journal file (SQLITE_CORRUPT) or
** unless a prior malloc() failed (SQLITE_NOMEM). Appropriate error
** codes are returned for all these occasions. Otherwise,
** SQLITE_OK is returned.
*/
int sqlite3PagerRollback(Pager *pPager){
int rc = SQLITE_OK;
PAGERTRACE2("ROLLBACK %d\n", PAGERID(pPager));
if( !pPager->dirtyCache || !pPager->journalOpen ){
rc = pager_end_transaction(pPager, pPager->setMaster);
}else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
if( pPager->state>=PAGER_EXCLUSIVE ){
pager_playback(pPager, 0);
}
rc = pPager->errCode;
}else{
if( pPager->state==PAGER_RESERVED ){
int rc2;
rc = pager_playback(pPager, 0);
rc2 = pager_end_transaction(pPager, pPager->setMaster);
if( rc==SQLITE_OK ){
rc = rc2;
}
}else{
rc = pager_playback(pPager, 0);
}
if( !MEMDB ){
pPager->dbSizeValid = 0;
}
/* If an error occurs during a ROLLBACK, we can no longer trust the pager
** cache. So call pager_error() on the way out to make any error
** persistent.
*/
rc = pager_error(pPager, rc);
}
return rc;
}
/*
** Return TRUE if the database file is opened read-only. Return FALSE
** if the database is (in theory) writable.
*/
int sqlite3PagerIsreadonly(Pager *pPager){
return pPager->readOnly;
}
/*
** Return the number of references to the pager.
*/
int sqlite3PagerRefcount(Pager *pPager){
return sqlite3PcacheRefCount(pPager->pPCache);
}
/*
** Return the number of references to the specified page.
*/
int sqlite3PagerPageRefcount(DbPage *pPage){
return sqlite3PcachePageRefcount(pPage);
}
#ifdef SQLITE_TEST
/*
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
static int a[11];
a[0] = sqlite3PcacheRefCount(pPager->pPCache);
a[1] = sqlite3PcachePagecount(pPager->pPCache);
a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
a[3] = pPager->dbSizeValid ? (int) pPager->dbSize : -1;
a[4] = pPager->state;
a[5] = pPager->errCode;
a[6] = pPager->nHit;
a[7] = pPager->nMiss;
a[8] = 0; /* Used to be pPager->nOvfl */
a[9] = pPager->nRead;
a[10] = pPager->nWrite;
return a;
}
int sqlite3PagerIsMemdb(Pager *pPager){
return MEMDB;
}
#endif
/*
** Set the statement rollback point.
**
** This routine should be called with the transaction journal already
** open. A new statement journal is created that can be used to rollback
** changes of a single SQL command within a larger transaction.
*/
static int pagerStmtBegin(Pager *pPager){
int rc;
assert( !pPager->stmtInUse );
assert( pPager->state>=PAGER_SHARED );
assert( pPager->dbSizeValid );
PAGERTRACE2("STMT-BEGIN %d\n", PAGERID(pPager));
if( !pPager->journalOpen ){
pPager->stmtAutoopen = 1;
return SQLITE_OK;
}
assert( pPager->journalOpen );
assert( pPager->pInStmt==0 );
pPager->pInStmt = sqlite3BitvecCreate(pPager->dbSize);
if( pPager->pInStmt==0 ){
/* sqlite3OsLock(pPager->fd, SHARED_LOCK); */
return SQLITE_NOMEM;
}
pPager->stmtJSize = pPager->journalOff;
pPager->stmtSize = pPager->dbSize;
pPager->stmtHdrOff = 0;
pPager->stmtCksum = pPager->cksumInit;
if( !pPager->stmtOpen ){
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
sqlite3MemJournalOpen(pPager->stfd);
}else{
rc = sqlite3PagerOpentemp(pPager, pPager->stfd, SQLITE_OPEN_SUBJOURNAL);
if( rc ){
goto stmt_begin_failed;
}
}
pPager->stmtOpen = 1;
pPager->stmtNRec = 0;
}
pPager->stmtInUse = 1;
return SQLITE_OK;
stmt_begin_failed:
if( pPager->pInStmt ){
sqlite3BitvecDestroy(pPager->pInStmt);
pPager->pInStmt = 0;
}
return rc;
}
int sqlite3PagerStmtBegin(Pager *pPager){
int rc;
rc = pagerStmtBegin(pPager);
return rc;
}
/*
** Commit a statement.
*/
int sqlite3PagerStmtCommit(Pager *pPager){
if( pPager->stmtInUse ){
PAGERTRACE2("STMT-COMMIT %d\n", PAGERID(pPager));
sqlite3BitvecDestroy(pPager->pInStmt);
pPager->pInStmt = 0;
pPager->stmtNRec = 0;
pPager->stmtInUse = 0;
if( sqlite3IsMemJournal(pPager->stfd) ){
sqlite3OsTruncate(pPager->stfd, 0);
}
}
pPager->stmtAutoopen = 0;
return SQLITE_OK;
}
/*
** Rollback a statement.
*/
int sqlite3PagerStmtRollback(Pager *pPager){
int rc;
if( pPager->stmtInUse ){
PAGERTRACE2("STMT-ROLLBACK %d\n", PAGERID(pPager));
rc = pager_stmt_playback(pPager);
sqlite3PagerStmtCommit(pPager);
}else{
rc = SQLITE_OK;
}
pPager->stmtAutoopen = 0;
return rc;
}
/*
** Return the full pathname of the database file.
*/
const char *sqlite3PagerFilename(Pager *pPager){
return pPager->zFilename;
}
/*
** Return the VFS structure for the pager.
*/
const sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
return pPager->pVfs;
}
/*
** Return the file handle for the database file associated
** with the pager. This might return NULL if the file has
** not yet been opened.
*/
sqlite3_file *sqlite3PagerFile(Pager *pPager){
return pPager->fd;
}
/*
** Return the directory of the database file.
*/
const char *sqlite3PagerDirname(Pager *pPager){
return pPager->zDirectory;
}
/*
** Return the full pathname of the journal file.
*/
const char *sqlite3PagerJournalname(Pager *pPager){
return pPager->zJournal;
}
/*
** Return true if fsync() calls are disabled for this pager. Return FALSE
** if fsync()s are executed normally.
*/
int sqlite3PagerNosync(Pager *pPager){
return pPager->noSync;
}
#ifdef SQLITE_HAS_CODEC
/*
** Set the codec for this pager
*/
void sqlite3PagerSetCodec(
Pager *pPager,
void *(*xCodec)(void*,void*,Pgno,int),
void *pCodecArg
){
pPager->xCodec = xCodec;
pPager->pCodecArg = pCodecArg;
}
#endif
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Move the page pPg to location pgno in the file.
**
** There must be no references to the page previously located at
** pgno (which we call pPgOld) though that page is allowed to be
** in cache. If the page previously located at pgno is not already
** in the rollback journal, it is not put there by by this routine.
**
** References to the page pPg remain valid. Updating any
** meta-data associated with pPg (i.e. data stored in the nExtra bytes
** allocated along with the page) is the responsibility of the caller.
**
** A transaction must be active when this routine is called. It used to be
** required that a statement transaction was not active, but this restriction
** has been removed (CREATE INDEX needs to move a page when a statement
** transaction is active).
**
** If the fourth argument, isCommit, is non-zero, then this page is being
** moved as part of a database reorganization just before the transaction
** is being committed. In this case, it is guaranteed that the database page
** pPg refers to will not be written to again within this transaction.
*/
int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
PgHdr *pPgOld; /* The page being overwritten. */
Pgno needSyncPgno = 0;
assert( pPg->nRef>0 );
PAGERTRACE5("MOVE %d page %d (needSync=%d) moves to %d\n",
PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno);
IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
pager_get_content(pPg);
/* If the journal needs to be sync()ed before page pPg->pgno can
** be written to, store pPg->pgno in local variable needSyncPgno.
**
** If the isCommit flag is set, there is no need to remember that
** the journal needs to be sync()ed before database page pPg->pgno
** can be written to. The caller has already promised not to write to it.
*/
if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
needSyncPgno = pPg->pgno;
assert( pageInJournal(pPg) || pPg->pgno>pPager->origDbSize );
assert( pPg->flags&PGHDR_DIRTY );
assert( pPager->needSync );
}
/* If the cache contains a page with page-number pgno, remove it
** from its hash chain. Also, if the PgHdr.needSync was set for
** page pgno before the 'move' operation, it needs to be retained
** for the page moved there.
*/
pPg->flags &= ~PGHDR_NEED_SYNC;
pPgOld = pager_lookup(pPager, pgno);
assert( !pPgOld || pPgOld->nRef==1 );
if( pPgOld ){
pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
}
sqlite3PcacheMove(pPg, pgno);
if( pPgOld ){
sqlite3PcacheDrop(pPgOld);
}
sqlite3PcacheMakeDirty(pPg);
pPager->dirtyCache = 1;
pPager->dbModified = 1;
if( needSyncPgno ){
/* If needSyncPgno is non-zero, then the journal file needs to be
** sync()ed before any data is written to database file page needSyncPgno.
** Currently, no such page exists in the page-cache and the
** "is journaled" bitvec flag has been set. This needs to be remedied by
** loading the page into the pager-cache and setting the PgHdr.needSync
** flag.
**
** If the attempt to load the page into the page-cache fails, (due
** to a malloc() or IO failure), clear the bit in the pInJournal[]
** array. Otherwise, if the page is loaded and written again in
** this transaction, it may be written to the database file before
** it is synced into the journal file. This way, it may end up in
** the journal file twice, but that is not a problem.
**
** The sqlite3PagerGet() call may cause the journal to sync. So make
** sure the Pager.needSync flag is set too.
*/
int rc;
PgHdr *pPgHdr;
assert( pPager->needSync );
rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr);
if( rc!=SQLITE_OK ){
if( pPager->pInJournal && needSyncPgno<=pPager->origDbSize ){
sqlite3BitvecClear(pPager->pInJournal, needSyncPgno);
}
return rc;
}
pPager->needSync = 1;
assert( pPager->noSync==0 && !MEMDB );
pPgHdr->flags |= PGHDR_NEED_SYNC;
sqlite3PcacheMakeDirty(pPgHdr);
sqlite3PagerUnref(pPgHdr);
}
return SQLITE_OK;
}
#endif
/*
** Return a pointer to the data for the specified page.
*/
void *sqlite3PagerGetData(DbPage *pPg){
assert( pPg->nRef>0 || pPg->pPager->memDb );
return pPg->pData;
}
/*
** Return a pointer to the Pager.nExtra bytes of "extra" space
** allocated along with the specified page.
*/
void *sqlite3PagerGetExtra(DbPage *pPg){
Pager *pPager = pPg->pPager;
return (pPager?pPg->pExtra:0);
}
/*
** Get/set the locking-mode for this pager. Parameter eMode must be one
** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
** the locking-mode is set to the value specified.
**
** The returned value is either PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
** locking-mode.
*/
int sqlite3PagerLockingMode(Pager *pPager, int eMode){
assert( eMode==PAGER_LOCKINGMODE_QUERY
|| eMode==PAGER_LOCKINGMODE_NORMAL
|| eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_QUERY<0 );
assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
if( eMode>=0 && !pPager->tempFile ){
pPager->exclusiveMode = eMode;
}
return (int)pPager->exclusiveMode;
}
/*
** Get/set the journal-mode for this pager. Parameter eMode must be one of:
**
** PAGER_JOURNALMODE_QUERY
** PAGER_JOURNALMODE_DELETE
** PAGER_JOURNALMODE_TRUNCATE
** PAGER_JOURNALMODE_PERSIST
** PAGER_JOURNALMODE_OFF
**
** If the parameter is not _QUERY, then the journal-mode is set to the
** value specified.
**
** The returned indicate the current (possibly updated)
** journal-mode.
*/
int sqlite3PagerJournalMode(Pager *pPager, int eMode){
if( !MEMDB ){
assert( eMode==PAGER_JOURNALMODE_QUERY
|| eMode==PAGER_JOURNALMODE_DELETE
|| eMode==PAGER_JOURNALMODE_TRUNCATE
|| eMode==PAGER_JOURNALMODE_PERSIST
|| eMode==PAGER_JOURNALMODE_OFF
|| eMode==PAGER_JOURNALMODE_MEMORY );
assert( PAGER_JOURNALMODE_QUERY<0 );
if( eMode>=0 ){
pPager->journalMode = eMode;
}else{
assert( eMode==PAGER_JOURNALMODE_QUERY );
}
}
return (int)pPager->journalMode;
}
/*
** Get/set the size-limit used for persistent journal files.
*/
i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
if( iLimit>=-1 ){
pPager->journalSizeLimit = iLimit;
}
return pPager->journalSizeLimit;
}
#endif /* SQLITE_OMIT_DISKIO */