/* ** 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 1.583 2009/04/28 05:27:20 danielk1977 Exp $ */ #ifndef SQLITE_OMIT_DISKIO #include "sqliteInt.h" /* ** Macros for troubleshooting. Normally turned off */ #if 0 int sqlite3PagerTrace=1; /* True to enable tracing */ #define sqlite3DebugPrintf printf #define PAGERTRACE(X) if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; } #else #define PAGERTRACE(X) #endif /* ** The following two macros are used within the PAGERTRACE() 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 /* ** 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 /* ** The maximum allowed sector size. 16MB. If the xSectorsize() method ** returns a value larger than this, then MAX_SECTOR_SIZE is used instead. ** This could conceivably cause corruption following a power failure on ** such a system. This is currently an undocumented limit. */ #define MAX_SECTOR_SIZE 0x0100000 /* ** An instance of the following structure is allocated for each active ** savepoint and statement transaction in the system. All such structures ** are stored in the Pager.aSavepoint[] array, which is allocated and ** resized using sqlite3Realloc(). ** ** When a savepoint is created, the PagerSavepoint.iHdrOffset field is ** set to 0. If a journal-header is written into the main journal while ** the savepoint is active, then iHdrOffset is set to the byte offset ** immediately following the last journal record written into the main ** journal before the journal-header. This is required during savepoint ** rollback (see pagerPlaybackSavepoint()). */ typedef struct PagerSavepoint PagerSavepoint; struct PagerSavepoint { i64 iOffset; /* Starting offset in main journal */ i64 iHdrOffset; /* See above */ Bitvec *pInSavepoint; /* Set of pages in this savepoint */ Pgno nOrig; /* Original number of pages in file */ Pgno iSubRec; /* Index of first record in sub-journal */ }; /* ** A open page cache is an instance of the following structure. ** ** errCode ** ** 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. ** ** dbSizeValid, dbSize, dbOrigSize, dbFileSize ** ** Managing the size of the database file in pages is a little complicated. ** The variable Pager.dbSize contains the number of pages that the database ** image currently contains. As the database image grows or shrinks this ** variable is updated. The variable Pager.dbFileSize contains the number ** of pages in the database file. This may be different from Pager.dbSize ** if some pages have been appended to the database image but not yet written ** out from the cache to the actual file on disk. Or if the image has been ** truncated by an incremental-vacuum operation. The Pager.dbOrigSize variable ** contains the number of pages in the database image when the current ** transaction was opened. The contents of all three of these variables is ** only guaranteed to be correct if the boolean Pager.dbSizeValid is true. ** ** TODO: Under what conditions is dbSizeValid set? Cleared? ** ** changeCountDone ** ** This boolean variable is used to make sure that the change-counter ** (the 4-byte header field at byte offset 24 of the database file) is ** not updated more often than necessary. ** ** It is set to true when the change-counter field is updated, which ** can only happen if an exclusive lock is held on the database file. ** It is cleared (set to false) whenever an exclusive lock is ** relinquished on the database file. Each time a transaction is committed, ** The changeCountDone flag is inspected. If it is true, the work of ** updating the change-counter is omitted for the current transaction. ** ** This mechanism means that when running in exclusive mode, a connection ** need only update the change-counter once, for the first transaction ** committed. ** ** dbModified ** ** The dbModified flag is set whenever a database page is dirtied. ** It is cleared at the end of each transaction. ** ** It is used when committing or otherwise ending a transaction. If ** the dbModified flag is clear then less work has to be done. ** ** journalStarted ** ** This flag is set whenever the the main journal is synced. ** ** The point of this flag is that it must be set after the ** first journal header in a journal file has been synced to disk. ** After this has happened, new pages appended to the database ** do not need the PGHDR_NEED_SYNC flag set, as they do not need ** to wait for a journal sync before they can be written out to ** the database file (see function pager_write()). ** ** setMaster ** ** This variable is used to ensure that the master journal file name ** (if any) is only written into the journal file once. ** ** When committing a transaction, the master journal file name (if any) ** may be written into the journal file while the pager is still in ** PAGER_RESERVED state (see CommitPhaseOne() for the action). It ** then attempts to upgrade to an exclusive lock. If this attempt ** fails, then SQLITE_BUSY may be returned to the user and the user ** may attempt to commit the transaction again later (calling ** CommitPhaseOne() again). This flag is used to ensure that the ** master journal name is only written to the journal file the first ** time CommitPhaseOne() is called. ** ** doNotSync ** ** This variable is set and cleared by sqlite3PagerWrite(). ** ** needSync ** ** TODO: It might be easier to set this variable in writeJournalHdr() ** and writeMasterJournal() only. Change its meaning to "unsynced data ** has been written to the journal". */ struct Pager { sqlite3_vfs *pVfs; /* OS functions to use for IO */ u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */ u8 journalMode; /* On of the PAGER_JOURNALMODE_* values */ u8 useJournal; /* Use a rollback journal on this file */ u8 noReadlock; /* Do not bother to obtain readlocks */ 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 tempFile; /* zFilename is a temporary file */ u8 readOnly; /* True for a read-only database */ u8 memDb; /* True to inhibit all file I/O */ /* The following block contains those class members that are dynamically ** modified during normal operations. The other variables in this structure ** are either constant throughout the lifetime of the pager, or else ** used to store configuration parameters that affect the way the pager ** operates. ** ** The 'state' variable is described in more detail along with the ** descriptions of the values it may take - PAGER_UNLOCK etc. Many of the ** other variables in this block are described in the comment directly ** above this class definition. */ u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */ u8 dbModified; /* True if there are any changes to the Db */ u8 needSync; /* True if an fsync() is needed on the journal */ u8 journalStarted; /* True if header of journal is synced */ u8 changeCountDone; /* Set after incrementing the change-counter */ u8 setMaster; /* True if a m-j name has been written to jrnl */ u8 doNotSync; /* Boolean. While true, do not spill the cache */ u8 dbSizeValid; /* Set when dbSize is correct */ Pgno dbSize; /* Number of pages in the database */ Pgno dbOrigSize; /* dbSize before the current transaction */ Pgno dbFileSize; /* Number of pages in the database file */ int errCode; /* One of several kinds of errors */ int nRec; /* Pages journalled since last j-header written */ u32 cksumInit; /* Quasi-random value added to every checksum */ u32 nSubRec; /* Number of records written to sub-journal */ Bitvec *pInJournal; /* One bit for each page in the database file */ sqlite3_file *fd; /* File descriptor for database */ sqlite3_file *jfd; /* File descriptor for main journal */ sqlite3_file *sjfd; /* File descriptor for sub-journal */ i64 journalOff; /* Current write offset in the journal file */ i64 journalHdr; /* Byte offset to previous journal header */ PagerSavepoint *aSavepoint; /* Array of active savepoints */ int nSavepoint; /* Number of elements in aSavepoint[] */ char dbFileVers[16]; /* Changes whenever database file changes */ u32 sectorSize; /* Assumed sector size during rollback */ int nExtra; /* Add this many bytes to each in-memory page */ u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */ int pageSize; /* Number of bytes in a page */ Pgno mxPgno; /* Maximum allowed size of the database */ char *zFilename; /* Name of the database file */ char *zJournal; /* Name of the journal file */ int (*xBusyHandler)(void*); /* Function to call when busy */ void *pBusyHandlerArg; /* Context argument for xBusyHandler */ #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 */ i64 journalSizeLimit; /* Size limit for persistent journal files */ PCache *pPCache; /* Pointer to page cache object */ sqlite3_backup *pBackup; /* Pointer to list of ongoing backup processes */ }; /* ** 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 being ** 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 of each page record in the journal is given by ** the following macro. */ #define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8) /* ** The journal header size for this pager. This is usually the same ** size as a single disk sector. See also setSectorSize(). */ #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 /* ** The maximum legal page number is (2^31 - 1). */ #define PAGER_MAX_PGNO 2147483647 #ifndef NDEBUG /* ** Usage: ** ** assert( assert_pager_state(pPager) ); */ static int assert_pager_state(Pager *pPager){ /* A temp-file is always in PAGER_EXCLUSIVE or PAGER_SYNCED state. */ assert( pPager->tempFile==0 || pPager->state>=PAGER_EXCLUSIVE ); /* The changeCountDone flag is always set for temp-files */ assert( pPager->tempFile==0 || pPager->changeCountDone ); return 1; } #endif /* ** Return true if it is necessary to write page *pPg into the sub-journal. ** A page needs to be written into the sub-journal if there exists one ** or more open savepoints for which: ** ** * The page-number is less than or equal to PagerSavepoint.nOrig, and ** * The bit corresponding to the page-number is not set in ** PagerSavepoint.pInSavepoint. */ static int subjRequiresPage(PgHdr *pPg){ Pgno pgno = pPg->pgno; Pager *pPager = pPg->pPager; int i; for(i=0; inSavepoint; i++){ PagerSavepoint *p = &pPager->aSavepoint[i]; if( p->nOrig>=pgno && 0==sqlite3BitvecTest(p->pInSavepoint, pgno) ){ return 1; } } return 0; } /* ** Return true if the page is already in the journal file. */ 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); } /* ** The argument to this macro is a file descriptor (type sqlite3_file*). ** Return 0 if it is not open, or non-zero (but not 1) if it is. ** ** This is so that expressions can be written as: ** ** if( isOpen(pPager->jfd) ){ ... ** ** instead of ** ** if( pPager->jfd->pMethods ){ ... */ #define isOpen(pFd) ((pFd)->pMethods) /* ** If file pFd is open, call sqlite3OsUnlock() on it. */ static int osUnlock(sqlite3_file *pFd, int eLock){ if( !isOpen(pFd) ){ 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. ** ** The optimization is also always enabled for temporary files. It is ** an error to call this function if pPager is opened on an in-memory ** database. ** ** 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){ assert( !MEMDB ); if( !pPager->tempFile ){ int dc; /* Device characteristics */ int nSector; /* Sector size */ int szPage; /* Page size */ assert( isOpen(pPager->fd) ); dc = sqlite3OsDeviceCharacteristics(pPager->fd); nSector = pPager->sectorSize; szPage = pPager->pageSize; assert(SQLITE_IOCAP_ATOMIC512==(512>>8)); assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8)); if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){ return 0; } } return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager); } #endif /* ** 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; ipPager->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. ** This function attempts to read a master journal file name from the ** end of the file and, if successful, copies it into memory supplied ** by the caller. See comments above writeMasterJournal() for the format ** used to store a master journal file name at the end of a journal file. ** ** 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 a master journal file name is present at the end of the journal ** file, then it is copied into the buffer pointed to by zMaster. A ** nul-terminator byte is appended to the buffer following the master ** journal file name. ** ** If it is determined that no master journal file name is present ** zMaster[0] is set to 0 and SQLITE_OK returned. ** ** If an error occurs while reading from the journal file, an SQLite ** error code is returned. */ static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){ int rc; /* Return code */ u32 len; /* Length in bytes of master journal name */ i64 szJ; /* Total size in bytes of journal file pJrnl */ u32 cksum; /* MJ checksum value read from journal */ u32 u; /* Unsigned loop counter */ unsigned char aMagic[8]; /* A buffer to hold the magic header */ zMaster[0] = '\0'; if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ)) || szJ<16 || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len)) || len>=nMaster || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum)) || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8)) || memcmp(aMagic, aJournalMagic, 8) || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len)) ){ return rc; } /* See if the checksum matches the master journal name */ for(u=0; ujournalOff, assuming a sector ** size of pPager->sectorSize bytes. ** ** i.e for a sector size of 512: ** ** Pager.journalOff Return value ** --------------------------------------- ** 0 0 ** 512 512 ** 100 512 ** 2000 2048 ** */ static i64 journalHdrOffset(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)jfd) ); if( pPager->journalOff ){ const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */ IOTRACE(("JZEROHDR %p\n", pPager)) if( doTruncate || iLimit==0 ){ rc = sqlite3OsTruncate(pPager->jfd, 0); }else{ static const char zeroHdr[28] = {0}; 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; /* Return code */ char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */ u32 nHeader = pPager->pageSize; /* Size of buffer pointed to by zHeader */ u32 nWrite; /* Bytes of header sector written */ int ii; /* Loop counter */ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ if( nHeader>JOURNAL_HDR_SZ(pPager) ){ nHeader = JOURNAL_HDR_SZ(pPager); } /* If there are active savepoints and any of them were created ** since the most recent journal header was written, update the ** PagerSavepoint.iHdrOffset fields now. */ for(ii=0; iinSavepoint; ii++){ if( pPager->aSavepoint[ii].iHdrOffset==0 ){ pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff; } } pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager); 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 occurred 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( isOpen(pPager->fd) || 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->dbOrigSize); /* The assumed sector size for this process */ put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize); /* The page size */ put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize); /* 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)+20], 0, nHeader-(sizeof(aJournalMagic)+20)); /* In theory, it is only necessary to write the 28 bytes that the ** journal header consumes to the journal file here. Then increment the ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next ** record is written to the following sector (leaving a gap in the file ** that will be implicitly filled in by the OS). ** ** However it has been discovered that on some systems this pattern can ** be significantly slower than contiguously writing data to the file, ** even if that means explicitly writing data to the block of ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what ** is done. ** ** The loop is required here in case the sector-size is larger than the ** database page size. Since the zHeader buffer is only Pager.pageSize ** bytes in size, more than one call to sqlite3OsWrite() may be required ** to populate the entire journal header sector. */ for(nWrite=0; rc==SQLITE_OK&&nWritejournalHdr, 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. The current location in the journal file is given by ** pPager->journalOff. See comments above function writeJournalHdr() for ** a description of the journal header format. ** ** If the header is read successfully, *pNRec is set to the number of ** page records following this header and *pDbSize 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 *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes ** cannot be read from the journal file an error code is returned. */ static int readJournalHdr( Pager *pPager, /* Pager object */ i64 journalSize, /* Size of the open journal file in bytes */ u32 *pNRec, /* OUT: Value read from the nRec field */ u32 *pDbSize /* OUT: Value of original database size field */ ){ int rc; /* Return code */ unsigned char aMagic[8]; /* A buffer to hold the magic header */ i64 iHdrOff; /* Offset of journal header being read */ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ /* Advance Pager.journalOff to the start of the next sector. If the ** journal file is too small for there to be a header stored at this ** point, return SQLITE_DONE. */ pPager->journalOff = journalHdrOffset(pPager); if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){ return SQLITE_DONE; } iHdrOff = pPager->journalOff; /* Read in the first 8 bytes of the journal header. If they do not match ** the magic string found at the start of each journal header, return ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise, ** proceed. */ rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff); if( rc ){ return rc; } if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){ return SQLITE_DONE; } /* Read the first three 32-bit fields of the journal header: The nRec ** field, the checksum-initializer and the database size at the start ** of the transaction. Return an error code if anything goes wrong. */ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize)) ){ return rc; } if( pPager->journalOff==0 ){ u32 iPageSize; /* Page-size field of journal header */ u32 iSectorSize; /* Sector-size field of journal header */ u16 iPageSize16; /* Copy of iPageSize in 16-bit variable */ /* Read the page-size and sector-size journal header fields. */ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize)) ){ return rc; } /* Check that the values read from the page-size and sector-size fields ** are within range. To be 'in range', both values need to be a power ** of two greater than or equal to 512, and not greater than their ** respective compile time maximum limits. */ if( iPageSize<512 || iSectorSize<512 || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE || ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0 ){ /* If the either the page-size or sector-size in the journal-header is ** invalid, then the process that wrote the journal-header must have ** crashed before the header was synced. In this case stop reading ** the journal file here. */ return SQLITE_DONE; } /* Update the page-size to match the value read from the journal. ** Use a testcase() macro to make sure that malloc failure within ** PagerSetPagesize() is tested. */ iPageSize16 = (u16)iPageSize; rc = sqlite3PagerSetPagesize(pPager, &iPageSize16); testcase( rc!=SQLITE_OK ); assert( rc!=SQLITE_OK || iPageSize16==(u16)iPageSize ); /* 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. */ pPager->sectorSize = iSectorSize; } pPager->journalOff += JOURNAL_HDR_SZ(pPager); return rc; } /* ** 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: Master journal filename in utf-8. ** + 4 bytes: N (length of master journal name in bytes, no nul-terminator). ** + 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, where each byte is interpreted as a signed 8-bit integer. ** ** 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; /* Return code */ int nMaster; /* Length of string zMaster */ i64 iHdrOff; /* Offset of header in journal file */ i64 jrnlSize; /* Size of journal file on disk */ u32 cksum = 0; /* Checksum of string zMaster */ if( !zMaster || pPager->setMaster || pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->journalMode==PAGER_JOURNALMODE_OFF ){ return SQLITE_OK; } pPager->setMaster = 1; assert( isOpen(pPager->jfd) ); /* Calculate the length in bytes and the checksum of zMaster */ for(nMaster=0; zMaster[nMaster]; nMaster++){ cksum += zMaster[nMaster]; } /* 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 ){ pPager->journalOff = journalHdrOffset(pPager); } iHdrOff = pPager->journalOff; /* Write the master journal data to the end of the journal file. If ** an error occurs, return the error code to the caller. */ if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager)))) || (0 != (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4))) || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster))) || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum))) || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, iHdrOff+4+nMaster+8))) ){ return rc; } pPager->journalOff += (nMaster+20); 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( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize)) && jrnlSize>pPager->journalOff ){ rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff); } return rc; } /* ** Find a page in the hash table given its page number. Return ** a pointer to the page or NULL if the requested page is not ** already in memory. */ static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){ PgHdr *p; /* Return value */ /* It is not possible for a call to PcacheFetch() with createFlag==0 to ** fail, since no attempt to allocate dynamic memory will be made. */ (void)sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p); return p; } /* ** Unless the pager is in error-state, discard all in-memory pages. If ** the pager is in error-state, then this call is a no-op. ** ** TODO: Why can we not reset the pager while in error state? */ static void pager_reset(Pager *pPager){ if( SQLITE_OK==pPager->errCode ){ sqlite3BackupRestart(pPager->pBackup); sqlite3PcacheClear(pPager->pPCache); pPager->dbSizeValid = 0; } } /* ** Free all structures in the Pager.aSavepoint[] array and set both ** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal ** if it is open and the pager is not in exclusive mode. */ static void releaseAllSavepoints(Pager *pPager){ int ii; /* Iterator for looping through Pager.aSavepoint */ for(ii=0; iinSavepoint; ii++){ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); } if( !pPager->exclusiveMode ){ sqlite3OsClose(pPager->sjfd); } sqlite3_free(pPager->aSavepoint); pPager->aSavepoint = 0; pPager->nSavepoint = 0; pPager->nSubRec = 0; } /* ** Set the bit number pgno in the PagerSavepoint.pInSavepoint ** bitvecs of all open savepoints. Return SQLITE_OK if successful ** or SQLITE_NOMEM if a malloc failure occurs. */ static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){ int ii; /* Loop counter */ int rc = SQLITE_OK; /* Result code */ for(ii=0; iinSavepoint; ii++){ PagerSavepoint *p = &pPager->aSavepoint[ii]; if( pgno<=p->nOrig ){ rc |= sqlite3BitvecSet(p->pInSavepoint, pgno); testcase( rc==SQLITE_NOMEM ); assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); } } return rc; } /* ** Unlock the database file. This function is a no-op if the pager ** is in exclusive mode. ** ** 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; /* Return code */ /* 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. */ sqlite3OsClose(pPager->jfd); sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; releaseAllSavepoints(pPager); /* If the file is unlocked, somebody else might change it. The ** values stored in Pager.dbSize etc. might become invalid if ** this happens. TODO: Really, this doesn't need to be cleared ** until the change-counter check fails in pagerSharedLock(). */ pPager->dbSizeValid = 0; rc = osUnlock(pPager->fd, NO_LOCK); if( rc ){ pPager->errCode = rc; } IOTRACE(("UNLOCK %p\n", pPager)) /* 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); } pPager->changeCountDone = 0; pPager->state = PAGER_UNLOCK; } } /* ** This function should be called when an IOERR, CORRUPT or FULL error ** may have occurred. 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 occurred, then the rollback journal may need ** to be replayed to restore the contents of the database file (as if ** it were a hot-journal). */ 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; } /* ** 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 at this time. Instead, pager_unlock() is called. The ** call to pager_unlock() will discard all in-memory pages, unlock ** the database file and clear the error state. If this means that ** there is a hot-journal left in the file-system, the next connection ** to obtain a shared lock on the pager (which may be this one) will ** roll it back. ** ** If the pager has not already entered the error state, but an IO or ** malloc error occurs during a rollback, then this will itself cause ** the pager to enter the error state. Which will be cleared by the ** call to pager_unlock(), as described above. */ static void pagerUnlockAndRollback(Pager *pPager){ if( pPager->errCode==SQLITE_OK && pPager->state>=PAGER_RESERVED ){ sqlite3BeginBenignMalloc(); sqlite3PagerRollback(pPager); sqlite3EndBenignMalloc(); } pager_unlock(pPager); } /* ** This routine ends a transaction. A transaction is usually ended by ** either a COMMIT or a ROLLBACK operation. This routine may be called ** after rollback of a hot-journal, or if an error occurs while opening ** the journal file or writing the very first journal-header of a ** database transaction. ** ** If the pager is in PAGER_SHARED or PAGER_UNLOCK state when this ** routine is called, it is a no-op (returns SQLITE_OK). ** ** Otherwise, any active savepoints are released. ** ** If the journal file is open, then it is "finalized". Once a journal ** file has been finalized it is not possible to use it to roll back a ** transaction. Nor will it be considered to be a hot-journal by this ** or any other database connection. Exactly how a journal is finalized ** depends on whether or not the pager is running in exclusive mode and ** the current journal-mode (Pager.journalMode value), as follows: ** ** journalMode==MEMORY ** Journal file descriptor is simply closed. This destroys an ** in-memory journal. ** ** journalMode==TRUNCATE ** Journal file is truncated to zero bytes in size. ** ** journalMode==PERSIST ** The first 28 bytes of the journal file are zeroed. This invalidates ** the first journal header in the file, and hence the entire journal ** file. An invalid journal file cannot be rolled back. ** ** journalMode==DELETE ** The journal file is closed and deleted using sqlite3OsDelete(). ** ** If the pager is running in exclusive mode, this method of finalizing ** the journal file is never used. Instead, if the journalMode is ** DELETE and the pager is in exclusive mode, the method described under ** journalMode==PERSIST is used instead. ** ** After the journal is finalized, if running in non-exclusive mode, the ** pager moves to PAGER_SHARED state (and downgrades the lock on the ** database file accordingly). ** ** If the pager is running in exclusive mode and is in PAGER_SYNCED state, ** it moves to PAGER_EXCLUSIVE. No locks are downgraded when running in ** exclusive mode. ** ** SQLITE_OK is returned if no error occurs. If an error occurs during ** any of the IO operations to finalize the journal file or unlock the ** database then the IO error code is returned to the user. If the ** operation to finalize the journal file fails, then the code still ** tries to unlock the database file if not in exclusive mode. If the ** unlock operation fails as well, then the first error code related ** to the first error encountered (the journal finalization one) is ** returned. */ static int pager_end_transaction(Pager *pPager, int hasMaster){ int rc = SQLITE_OK; /* Error code from journal finalization operation */ int rc2 = SQLITE_OK; /* Error code from db file unlock operation */ if( pPager->statejfd) || pPager->pInJournal==0 ); if( isOpen(pPager->jfd) ){ /* TODO: There's a problem here if a journal-file was opened in MEMORY ** mode and then the journal-mode is changed to TRUNCATE or PERSIST ** during the transaction. This code should be changed to assume ** that the journal mode has not changed since the transaction was ** started. And the sqlite3PagerJournalMode() function should be ** changed to make sure that this is the case too. */ /* Finalize the journal file. */ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){ int isMemoryJournal = sqlite3IsMemJournal(pPager->jfd); sqlite3OsClose(pPager->jfd); if( !isMemoryJournal ){ rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); } }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){ if( pPager->journalOff==0 ){ rc = SQLITE_OK; }else{ rc = sqlite3OsTruncate(pPager->jfd, 0); } 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); if( rc==SQLITE_OK && !pPager->tempFile ){ rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); } } #ifdef SQLITE_CHECK_PAGES sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash); #endif sqlite3PcacheCleanAll(pPager->pPCache); sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; pPager->nRec = 0; } if( !pPager->exclusiveMode ){ rc2 = osUnlock(pPager->fd, SHARED_LOCK); pPager->state = PAGER_SHARED; pPager->changeCountDone = 0; }else if( pPager->state==PAGER_SYNCED ){ pPager->state = PAGER_EXCLUSIVE; } pPager->setMaster = 0; pPager->needSync = 0; pPager->dbModified = 0; /* TODO: Is this optimal? Why is the db size invalidated here ** when the database file is not unlocked? */ pPager->dbOrigSize = 0; sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize); if( !MEMDB ){ pPager->dbSizeValid = 0; } return (rc==SQLITE_OK?rc2:rc); } /* ** Parameter aData must point to a buffer of pPager->pageSize bytes ** of data. Compute and return a checksum based ont the contents of the ** page of data and the current value of pPager->cksumInit. ** ** This is not a real checksum. It is really just the sum of the ** random initial value (pPager->cksumInit) and every 200th byte ** of the page data, starting with byte offset (pPager->pageSize%200). ** Each byte is interpreted as an 8-bit unsigned integer. ** ** Changing the formula used to compute this checksum results in an ** incompatible journal file format. ** ** 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. */ static u32 pager_cksum(Pager *pPager, const u8 *aData){ u32 cksum = pPager->cksumInit; /* Checksum value to return */ int i = pPager->pageSize-200; /* Loop counter */ while( i>0 ){ cksum += aData[i]; i -= 200; } return cksum; } /* ** Read a single page from either the journal file (if isMainJrnl==1) or ** from the sub-journal (if isMainJrnl==0) and playback that page. ** The page begins at offset *pOffset into the file. The *pOffset ** value is increased to the start of the next page in the journal. ** ** 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. ** ** If the page number of the page record read from the (sub-)journal file ** is greater than the current value of Pager.dbSize, then playback is ** skipped and SQLITE_OK is returned. ** ** If pDone is not NULL, then it is a record of pages that have already ** been played back. If the page at *pOffset has already been played back ** (if the corresponding pDone bit is set) then skip the playback. ** Make sure the pDone bit corresponding to the *pOffset page is set ** prior to returning. ** ** If the page record is successfully read from the (sub-)journal file ** and played back, then SQLITE_OK is returned. If an IO error occurs ** while reading the record from the (sub-)journal file or while writing ** to the database file, then the IO error code is returned. If data ** is successfully read from the (sub-)journal file but appears to be ** corrupted, SQLITE_DONE is returned. Data is considered corrupted in ** two circumstances: ** ** * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or ** * If the record is being rolled back from the main journal file ** and the checksum field does not match the record content. ** ** Neither of these two scenarios are possible during a savepoint rollback. ** ** If this is a savepoint rollback, then memory may have to be dynamically ** allocated by this function. If this is the case and an allocation fails, ** SQLITE_NOMEM is returned. */ static int pager_playback_one_page( Pager *pPager, /* The pager being played back */ int isMainJrnl, /* 1 -> main journal. 0 -> sub-journal. */ int isUnsync, /* True if reading from unsynced main journal */ i64 *pOffset, /* Offset of record to playback */ int isSavepnt, /* True for a savepoint rollback */ Bitvec *pDone /* Bitvec of pages already played back */ ){ 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; /* Temporary storage for the page */ sqlite3_file *jfd; /* The file descriptor for the journal file */ assert( (isMainJrnl&~1)==0 ); /* isMainJrnl is 0 or 1 */ assert( (isSavepnt&~1)==0 ); /* isSavepnt is 0 or 1 */ assert( isMainJrnl || pDone ); /* pDone always used on sub-journals */ assert( isSavepnt || pDone==0 ); /* pDone never used on non-savepoint */ aData = (u8*)pPager->pTmpSpace; assert( aData ); /* Temp storage must have already been allocated */ /* Read the page number and page data from the journal or sub-journal ** file. Return an error code to the caller if an IO error occurs. */ jfd = isMainJrnl ? pPager->jfd : pPager->sjfd; rc = read32bits(jfd, *pOffset, &pgno); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsRead(jfd, aData, pPager->pageSize, (*pOffset)+4); if( rc!=SQLITE_OK ) return rc; *pOffset += pPager->pageSize + 4 + isMainJrnl*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) ){ assert( !isSavepnt ); return SQLITE_DONE; } if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){ return SQLITE_OK; } if( isMainJrnl ){ rc = read32bits(jfd, (*pOffset)-4, &cksum); if( rc ) return rc; if( !isSavepnt && pager_cksum(pPager, aData)!=cksum ){ return SQLITE_DONE; } } if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){ return rc; } 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); assert( pPg || !MEMDB ); PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n", PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, aData), (isMainJrnl?"main-journal":"sub-journal") )); if( (pPager->state>=PAGER_EXCLUSIVE) && (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC)) && isOpen(pPager->fd) && !isUnsync ){ i64 ofst = (pgno-1)*(i64)pPager->pageSize; rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize, ofst); if( pgno>pPager->dbFileSize ){ pPager->dbFileSize = pgno; } sqlite3BackupUpdate(pPager->pBackup, pgno, aData); }else if( !isMainJrnl && pPg==0 ){ /* If this is a rollback of a savepoint and data was not written to ** the database and the page is not in-memory, there is a potential ** problem. When the page is next fetched by the b-tree layer, it ** will be read from the database file, which may or may not be ** current. ** ** There are a couple of different ways this can happen. All are quite ** obscure. When running in synchronous mode, this can only happen ** if the page is on the free-list at the start of the transaction, then ** populated, then moved using sqlite3PagerMovepage(). ** ** The solution is to add an in-memory page to the cache containing ** the data just read from the sub-journal. Mark the page as dirty ** and if the pager requires a journal-sync, then mark the page as ** requiring a journal-sync before it is written. */ assert( isSavepnt ); if( (rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1))!=SQLITE_OK ){ return rc; } pPg->flags &= ~PGHDR_NEED_READ; sqlite3PcacheMakeDirty(pPg); } 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 && (!isSavepnt || *pOffset<=pPager->journalHdr) ){ /* If the contents of this page were just restored from the main ** journal file, then its content must be as they were when the ** transaction was first opened. In this case we can mark the page ** as clean, since there will be no need to write it out to the. ** ** There is one exception to this rule. If the page is being rolled ** back as part of a savepoint (or statement) rollback from an ** unsynced portion of the main journal file, then it is not safe ** to mark the page as clean. This is because marking the page as ** clean will clear the PGHDR_NEED_SYNC flag. Since the page is ** already in the journal file (recorded in Pager.pInJournal) and ** the PGHDR_NEED_SYNC flag is cleared, if the page is written to ** again within this transaction, it will be marked as dirty but ** the PGHDR_NEED_SYNC flag will not be set. It could then potentially ** be written out into the database file before its journal file ** segment is synced. If a crash occurs during or following this, ** database corruption may ensue. */ 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; } #if !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST) /* ** This routine looks ahead into the main journal file and determines ** whether or not the next record (the record that begins at file ** offset pPager->journalOff) is a well-formed page record consisting ** of a valid page number, pPage->pageSize bytes of content, followed ** by a valid checksum. ** ** The pager never needs to know this in order to do its job. This ** routine is only used from with assert() and testcase() macros. */ static int pagerNextJournalPageIsValid(Pager *pPager){ Pgno pgno; /* The page number of the page */ u32 cksum; /* The page checksum */ int rc; /* Return code from read operations */ sqlite3_file *fd; /* The file descriptor from which we are reading */ u8 *aData; /* Content of the page */ /* Read the page number header */ fd = pPager->jfd; rc = read32bits(fd, pPager->journalOff, &pgno); if( rc!=SQLITE_OK ){ return 0; } /*NO_TEST*/ if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){ return 0; } /*NO_TEST*/ if( pgno>(Pgno)pPager->dbSize ){ return 0; } /*NO_TEST*/ /* Read the checksum */ rc = read32bits(fd, pPager->journalOff+pPager->pageSize+4, &cksum); if( rc!=SQLITE_OK ){ return 0; } /*NO_TEST*/ /* Read the data and verify the checksum */ aData = (u8*)pPager->pTmpSpace; rc = sqlite3OsRead(fd, aData, pPager->pageSize, pPager->journalOff+4); if( rc!=SQLITE_OK ){ return 0; } /*NO_TEST*/ if( pager_cksum(pPager, aData)!=cksum ){ return 0; } /*NO_TEST*/ /* Reach this point only if the page is valid */ return 1; } #endif /* !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST) */ /* ** 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. ** ** When a master journal file is created, it is populated with the names ** of all of its child journals, one after another, formatted as utf-8 ** encoded text. The end of each child journal file is marked with a ** nul-terminator byte (0x00). i.e. the entire contents of a master journal ** file for a transaction involving two databases might be: ** ** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00" ** ** A master journal file may only be deleted once all of its child ** journals have been rolled back. ** ** This function reads the contents of the master-journal file into ** memory and loops through each of the child journal names. For ** each child journal, it checks if: ** ** * if the child journal exists, and if so ** * if the child journal contains a reference to master journal ** file zMaster ** ** If a child journal can be found that matches both of the criteria ** above, this function returns without doing anything. Otherwise, if ** no such child journal can be found, file zMaster is deleted from ** the file-system using sqlite3OsDelete(). ** ** If an IO error within this function, an error code is returned. This ** function allocates memory by calling sqlite3Malloc(). If an allocation ** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors ** occur, SQLITE_OK is returned. ** ** TODO: This function allocates a single block of memory to load ** the entire contents of the master journal file. This could be ** a couple of kilobytes or so - potentially larger than the page ** size. */ static int pager_delmaster(Pager *pPager, const char *zMaster){ sqlite3_vfs *pVfs = pPager->pVfs; int rc; /* Return code */ sqlite3_file *pMaster; /* Malloc'd master-journal file descriptor */ sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */ char *zMasterJournal = 0; /* Contents of master journal file */ i64 nMasterJournal; /* Size of master journal file */ /* Allocate space for both the pJournal and pMaster file descriptors. ** If successful, open the master journal file for reading. */ pMaster = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2); pJournal = (sqlite3_file *)(((u8 *)pMaster) + pVfs->szOsFile); if( !pMaster ){ rc = SQLITE_NOMEM; }else{ const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MASTER_JOURNAL); rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0); } if( rc!=SQLITE_OK ) goto delmaster_out; rc = sqlite3OsFileSize(pMaster, &nMasterJournal); if( rc!=SQLITE_OK ) goto delmaster_out; if( nMasterJournal>0 ){ char *zJournal; char *zMasterPtr = 0; int nMasterPtr = pVfs->mxPathname+1; /* Load the entire master journal file into space obtained from ** sqlite3_malloc() and pointed to by zMasterJournal. */ zMasterJournal = (char *)sqlite3Malloc((int)nMasterJournal + nMasterPtr); if( !zMasterJournal ){ rc = SQLITE_NOMEM; goto delmaster_out; } zMasterPtr = &zMasterJournal[nMasterJournal]; rc = sqlite3OsRead(pMaster, zMasterJournal, (int)nMasterJournal, 0); if( rc!=SQLITE_OK ) goto delmaster_out; zJournal = zMasterJournal; while( (zJournal-zMasterJournal)pageSize bytes). If the file ** on disk is currently larger than nPage pages, then use the VFS ** xTruncate() method to truncate it. ** ** Or, it might might be the case that the file on disk is smaller than ** nPage pages. 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. ** ** If successful, return SQLITE_OK. If an IO error occurs while modifying ** the database file, return the error code to the caller. */ static int pager_truncate(Pager *pPager, Pgno nPage){ int rc = SQLITE_OK; if( pPager->state>=PAGER_EXCLUSIVE && isOpen(pPager->fd) ){ i64 currentSize, newSize; /* TODO: Is it safe to use Pager.dbFileSize here? */ rc = sqlite3OsFileSize(pPager->fd, ¤tSize); 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->dbFileSize = nPage; } } } return rc; } /* ** Set the value of the Pager.sectorSize variable for the given ** pager based on the value returned by the xSectorSize method ** of the open database file. The sector size will be used used ** to determine the size and alignment of journal header and ** master journal pointers within created journal files. ** ** For temporary files the effective sector size is always 512 bytes. ** ** Otherwise, for non-temporary files, the effective sector size is ** the value returned by the xSectorSize() method rounded up to 512 if ** it is less than 512, or rounded down to MAX_SECTOR_SIZE if it ** is greater than MAX_SECTOR_SIZE. */ static void setSectorSize(Pager *pPager){ assert( isOpen(pPager->fd) || pPager->tempFile ); if( !pPager->tempFile ){ /* Sector size doesn't matter for temporary files. Also, the file ** may not have been opened yet, in which case the OsSectorSize() ** call will segfault. */ pPager->sectorSize = sqlite3OsSectorSize(pPager->fd); } if( pPager->sectorSize<512 ){ pPager->sectorSize = 512; } if( pPager->sectorSize>MAX_SECTOR_SIZE ){ assert( MAX_SECTOR_SIZE>=512 ); pPager->sectorSize = MAX_SECTOR_SIZE; } } /* ** 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. ** ** The isHot parameter indicates that we are trying to rollback a journal ** that might be a hot journal. Or, it could be that the journal is ** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE. ** If the journal really is hot, reset the pager cache prior rolling ** back any content. If the journal is merely persistent, no reset is ** needed. */ 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 */ int needPagerReset; /* True to reset page prior to first page rollback */ /* Figure out how many records are in the journal. Abort early if ** the journal is empty. */ assert( isOpen(pPager->jfd) ); 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. ** ** TODO: Technically the following is an error because it assumes that ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c, ** mxPathname is 512, which is the same as the minimum allowable value ** for pageSize. */ 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; needPagerReset = isHot; /* This loop terminates either when a readJournalHdr() or ** pager_playback_one_page() call returns SQLITE_DONE or an IO error ** occurs. */ while( 1 ){ int isUnsync = 0; /* 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 = (int)((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. ** When rolling back a hot journal, nRec==0 always means that the next ** chunk of the journal contains zero pages to be rolled back. But ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in ** the journal, it means that the journal might contain additional ** pages that need to be rolled back and that the number of pages ** should be computed based on the journal file size. */ testcase( nRec==0 && !isHot && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff && ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0 && pagerNextJournalPageIsValid(pPager) ); if( nRec==0 && !isHot && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){ nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager)); isUnsync = 1; } /* 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; } pPager->dbSize = mxPg; } /* Copy original pages out of the journal and back into the ** database file and/or page cache. */ for(u=0; ujournalOff,0,0); if( rc!=SQLITE_OK ){ if( rc==SQLITE_DONE ){ rc = SQLITE_OK; pPager->journalOff = szJ; break; }else{ /* If we are unable to rollback, quit and return the error ** code. This will cause the pager to enter the error state ** so that no further harm will be done. Perhaps the next ** process to come along will be able to rollback the database. */ goto end_playback; } } } } /*NOTREACHED*/ assert( 0 ); end_playback: /* Following a rollback, the database file should be back in its original ** state prior to the start of the transaction, so invoke the ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the ** assertion that the transaction counter was modified. */ assert( pPager->fd->pMethods==0 || sqlite3OsFileControl(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0)>=SQLITE_OK ); /* If this playback is happening automatically as a result of an IO or ** malloc error that occurred after the change-counter was updated but ** before the transaction was committed, then the change-counter ** modification may just have been reverted. If this happens in exclusive ** mode, then subsequent transactions performed by the connection will not ** update the change-counter at all. This may lead to cache inconsistency ** problems for other processes at some point in the future. So, just ** in case this has happened, clear the changeCountDone flag now. */ pPager->changeCountDone = pPager->tempFile; if( rc==SQLITE_OK ){ zMaster = pPager->pTmpSpace; rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1); testcase( rc!=SQLITE_OK ); } if( rc==SQLITE_OK ){ rc = pager_end_transaction(pPager, zMaster[0]!='\0'); testcase( rc!=SQLITE_OK ); } 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); testcase( rc!=SQLITE_OK ); } /* 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 savepoint pSavepoint. Or, if pSavepoint==NULL, then playback ** the entire master journal file. The case pSavepoint==NULL occurs when ** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction ** savepoint. ** ** When pSavepoint is not NULL (meaning a non-transaction savepoint is ** being rolled back), then the rollback consists of up to three stages, ** performed in the order specified: ** ** * Pages are played back from the main journal starting at byte ** offset PagerSavepoint.iOffset and continuing to ** PagerSavepoint.iHdrOffset, or to the end of the main journal ** file if PagerSavepoint.iHdrOffset is zero. ** ** * If PagerSavepoint.iHdrOffset is not zero, then pages are played ** back starting from the journal header immediately following ** PagerSavepoint.iHdrOffset to the end of the main journal file. ** ** * Pages are then played back from the sub-journal file, starting ** with the PagerSavepoint.iSubRec and continuing to the end of ** the journal file. ** ** Throughout the rollback process, each time a page is rolled back, the ** corresponding bit is set in a bitvec structure (variable pDone in the ** implementation below). This is used to ensure that a page is only ** rolled back the first time it is encountered in either journal. ** ** If pSavepoint is NULL, then pages are only played back from the main ** journal file. There is no need for a bitvec in this case. ** ** In either case, before playback commences the Pager.dbSize variable ** is reset to the value that it held at the start of the savepoint ** (or transaction). No page with a page-number greater than this value ** is played back. If one is encountered it is simply skipped. */ static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){ i64 szJ; /* Effective size of the main journal */ i64 iHdrOff; /* End of first segment of main-journal records */ int rc = SQLITE_OK; /* Return code */ Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */ assert( pPager->state>=PAGER_SHARED ); /* Allocate a bitvec to use to store the set of pages rolled back */ if( pSavepoint ){ pDone = sqlite3BitvecCreate(pSavepoint->nOrig); if( !pDone ){ return SQLITE_NOMEM; } } /* Set the database size back to the value it was before the savepoint ** being reverted was opened. */ pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize; /* Use pPager->journalOff as the effective size of the main rollback ** journal. The actual file might be larger than this in ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST. But anything ** past pPager->journalOff is off-limits to us. */ szJ = pPager->journalOff; /* Begin by rolling back records from the main journal starting at ** PagerSavepoint.iOffset and continuing to the next journal header. ** There might be records in the main journal that have a page number ** greater than the current database size (pPager->dbSize) but those ** will be skipped automatically. Pages are added to pDone as they ** are played back. */ if( pSavepoint ){ iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ; pPager->journalOff = pSavepoint->iOffset; while( rc==SQLITE_OK && pPager->journalOffjournalOff, 1, pDone); } assert( rc!=SQLITE_DONE ); }else{ pPager->journalOff = 0; } /* Continue rolling back records out of the main journal starting at ** the first journal header seen and continuing until the effective end ** of the main journal file. Continue to skip out-of-range pages and ** continue adding pages rolled back to pDone. */ while( rc==SQLITE_OK && pPager->journalOffjournalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff" ** test is related to ticket #2565. See the discussion in the ** pager_playback() function for additional information. */ assert( !(nJRec==0 && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff && ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0 && pagerNextJournalPageIsValid(pPager)) ); if( nJRec==0 && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){ nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager)); } for(ii=0; rc==SQLITE_OK && iijournalOffjournalOff, 1, pDone); } assert( rc!=SQLITE_DONE ); } assert( rc!=SQLITE_OK || pPager->journalOff==szJ ); /* Finally, rollback pages from the sub-journal. Page that were ** previously rolled back out of the main journal (and are hence in pDone) ** will be skipped. Out-of-range pages are also skipped. */ if( pSavepoint ){ u32 ii; /* Loop counter */ i64 offset = pSavepoint->iSubRec*(4+pPager->pageSize); for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && iinSubRec; ii++){ assert( offset==ii*(4+pPager->pageSize) ); rc = pager_playback_one_page(pPager, 0, 0, &offset, 1, pDone); } assert( rc!=SQLITE_DONE ); } sqlite3BitvecDestroy(pDone); if( rc==SQLITE_OK ){ pPager->journalOff = szJ; } 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) ?1:0; pPager->fullSync = (level==3 && !pPager->tempFile) ?1:0; 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 *pFile. 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. ** ** The flags passed to the VFS layer xOpen() call are those specified ** by parameter vfsFlags ORed with the following: ** ** SQLITE_OPEN_READWRITE ** SQLITE_OPEN_CREATE ** SQLITE_OPEN_EXCLUSIVE ** SQLITE_OPEN_DELETEONCLOSE */ static int pagerOpentemp( Pager *pPager, /* The pager object */ sqlite3_file *pFile, /* Write the file descriptor here */ int vfsFlags /* Flags passed through to the VFS */ ){ int rc; /* Return code */ #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 || isOpen(pFile) ); return rc; } /* ** Set the busy handler function. ** ** The pager invokes the busy-handler if sqlite3OsLock() returns ** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock, ** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE ** lock. It does *not* invoke the busy handler when upgrading from ** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE ** (which occurs during hot-journal rollback). Summary: ** ** Transition | Invokes xBusyHandler ** -------------------------------------------------------- ** NO_LOCK -> SHARED_LOCK | Yes ** SHARED_LOCK -> RESERVED_LOCK | No ** SHARED_LOCK -> EXCLUSIVE_LOCK | No ** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes ** ** If the busy-handler callback returns non-zero, the lock is ** retried. If it returns zero, then the SQLITE_BUSY error is ** returned to the caller of the pager API function. */ void sqlite3PagerSetBusyhandler( Pager *pPager, /* Pager object */ int (*xBusyHandler)(void *), /* Pointer to busy-handler function */ void *pBusyHandlerArg /* Argument to pass to xBusyHandler */ ){ 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 modified (restored) ** as part of a transaction or savepoint 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; } /* ** Change the page size used by the Pager object. The new page size ** is passed in *pPageSize. ** ** If the pager is in the error state when this function is called, it ** is a no-op. The value returned is the error state error code (i.e. ** one of SQLITE_IOERR, SQLITE_CORRUPT or SQLITE_FULL). ** ** Otherwise, if all of the following are true: ** ** * the new page size (value of *pPageSize) is valid (a power ** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and ** ** * there are no outstanding page references, and ** ** * the database is either not an in-memory database or it is ** an in-memory database that currently consists of zero pages. ** ** then the pager object page size is set to *pPageSize. ** ** If the page size is changed, then this function uses sqlite3PagerMalloc() ** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt ** fails, SQLITE_NOMEM is returned and the page size remains unchanged. ** In all other cases, SQLITE_OK is returned. ** ** If the page size is not changed, either because one of the enumerated ** conditions above is not true, the pager was in error state when this ** function was called, or because the memory allocation attempt failed, ** then *pPageSize is set to the old, retained page size 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; sqlite3PageFree(pPager->pTmpSpace); pPager->pTmpSpace = pNew; sqlite3PcacheSetPageSize(pPager->pPCache, pageSize); } } *pPageSize = (u16)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. ** ** If the pager was opened on a transient file (zFilename==""), or ** opened on a file less than N bytes in size, the output buffer is ** zeroed and SQLITE_OK returned. The rationale for this is that this ** function is used to read database headers, and a new transient or ** zero sized database has a header than consists entirely of zeroes. ** ** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered, ** the error code is returned to the caller and the contents of the ** output buffer undefined. */ int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){ int rc = SQLITE_OK; memset(pDest, 0, N); assert( isOpen(pPager->fd) || pPager->tempFile ); if( isOpen(pPager->fd) ){ 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 database file associated ** with pPager. Normally, this is calculated as (/). ** However, if the file is between 1 and bytes in size, then ** this is considered a 1 page file. ** ** If the pager is in error state when this function is called, then the ** error state error code is returned and *pnPage left unchanged. Or, ** if the file system has to be queried for the size of the file and ** the query attempt returns an IO error, the IO error code is returned ** and *pnPage is left unchanged. ** ** Otherwise, if everything is successful, then SQLITE_OK is returned ** and *pnPage is set to the number of pages in the database. */ int sqlite3PagerPagecount(Pager *pPager, int *pnPage){ Pgno nPage; /* Value to return via *pnPage */ /* If the pager is already in the error state, return the error code. */ if( pPager->errCode ){ return pPager->errCode; } /* Determine the number of pages in the file. Store this in nPage. */ if( pPager->dbSizeValid ){ nPage = pPager->dbSize; }else{ int rc; /* Error returned by OsFileSize() */ i64 n = 0; /* File size in bytes returned by OsFileSize() */ assert( isOpen(pPager->fd) || pPager->tempFile ); if( isOpen(pPager->fd) && (0 != (rc = sqlite3OsFileSize(pPager->fd, &n))) ){ pager_error(pPager, rc); return rc; } if( n>0 && npageSize ){ nPage = 1; }else{ nPage = (Pgno)(n / pPager->pageSize); } if( pPager->state!=PAGER_UNLOCK ){ pPager->dbSize = nPage; pPager->dbFileSize = nPage; pPager->dbSizeValid = 1; } } /* If the current number of pages in the file is greater than the ** configured maximum pager number, increase the allowed limit so ** that the file can be read. */ if( nPage>pPager->mxPgno ){ pPager->mxPgno = (Pgno)nPage; } /* Set the output variable and return SQLITE_OK */ if( pnPage ){ *pnPage = nPage; } return SQLITE_OK; } /* ** Try to obtain a lock of type locktype on the database file. If ** a similar or greater lock is already held, this function is a no-op ** (returning SQLITE_OK immediately). ** ** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke ** the busy callback if the lock is currently not available. Repeat ** until the busy callback returns false or until the attempt to ** obtain the lock succeeds. ** ** Return SQLITE_OK on success and an error code if we cannot obtain ** the lock. If the lock is obtained successfully, set the Pager.state ** variable to locktype before returning. */ static int pager_wait_on_lock(Pager *pPager, int locktype){ int rc; /* Return code */ /* 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 ); /* Check that this is either a no-op (because the requested lock is ** already held, or one of the transistions that the busy-handler ** may be invoked during, according to the comment above ** sqlite3PagerSetBusyhandler(). */ assert( (pPager->state>=locktype) || (pPager->state==PAGER_UNLOCK && locktype==PAGER_SHARED) || (pPager->state==PAGER_RESERVED && locktype==PAGER_EXCLUSIVE) ); 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 = (u8)locktype; IOTRACE(("LOCK %p %d\n", pPager, locktype)) } } return rc; } /* ** Truncate the in-memory database file image to nPage pages. This ** function does not actually modify the database file on disk. It ** just sets the internal state of the pager object so that the ** truncation will be done when the current transaction is committed. */ void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){ assert( pPager->dbSizeValid ); assert( pPager->dbSize>=nPage ); assert( pPager->state>=PAGER_RESERVED ); pPager->dbSize = nPage; } /* ** 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 ){ pager_unlock(pPager); }else{ /* Set Pager.journalHdr to -1 for the benefit of the pager_playback() ** call which may be made from within pagerUnlockAndRollback(). If it ** is not -1, then the unsynced portion of an open journal file may ** be played back into the database. If a power failure occurs while ** this is happening, the database may become corrupt. */ pPager->journalHdr = -1; pagerUnlockAndRollback(pPager); } sqlite3EndBenignMalloc(); enable_simulated_io_errors(); PAGERTRACE(("CLOSE %d\n", PAGERID(pPager))); IOTRACE(("CLOSE %p\n", pPager)) sqlite3OsClose(pPager->fd); sqlite3PageFree(pPager->pTmpSpace); sqlite3PcacheClose(pPager->pPCache); assert( !pPager->aSavepoint && !pPager->pInJournal ); assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ); sqlite3_free(pPager); return SQLITE_OK; } #if !defined(NDEBUG) || defined(SQLITE_TEST) /* ** Return the page number for page pPg. */ Pgno sqlite3PagerPagenumber(DbPage *pPg){ return pPg->pgno; } #endif /* ** Increment the reference count for page pPg. */ void sqlite3PagerRef(DbPage *pPg){ sqlite3PcacheRef(pPg); } /* ** 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 and can be restored in the event of a hot-journal rollback. ** ** If the Pager.needSync flag is not set, then this function is a ** no-op. Otherwise, the actions required depend on the journal-mode ** and the device characteristics of the the file-system, as follows: ** ** * If the journal file is an in-memory journal file, no action need ** be taken. ** ** * Otherwise, if the device does not support the SAFE_APPEND property, ** then the nRec field of the most recently written journal header ** is updated to contain the number of journal records that have ** been written following it. If the pager is operating in full-sync ** mode, then the journal file is synced before this field is updated. ** ** * If the device does not support the SEQUENTIAL property, then ** journal file is synced. ** ** Or, in pseudo-code: ** ** if( NOT ){ ** if( NOT SAFE_APPEND ){ ** if( ) xSync(); ** ** } ** if( NOT SEQUENTIAL ) xSync(); ** } ** ** The Pager.needSync flag is never be set for temporary files, or any ** file operating in no-sync mode (Pager.noSync set to non-zero). ** ** If successful, this routine clears the PGHDR_NEED_SYNC flag of every ** page currently held in memory before returning SQLITE_OK. If an IO ** error is encountered, then the IO error code is returned to the caller. */ static int syncJournal(Pager *pPager){ if( pPager->needSync ){ assert( !pPager->tempFile ); if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){ int rc; /* Return code */ const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd); assert( isOpen(pPager->jfd) ); if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){ /* Variable iNRecOffset is set to the offset in the journal file ** of the nRec field of the most recently written journal header. ** This field will be updated following the xSync() operation ** on the journal file. */ i64 iNRecOffset = pPager->journalHdr + sizeof(aJournalMagic); /* This block deals with an obscure problem. If the last connection ** that wrote to this database was operating in persistent-journal ** mode, then the journal file may at this point actually be larger ** than Pager.journalOff bytes. If the next thing in the journal ** file happens to be a journal-header (written as part of the ** previous connections transaction), and a crash or power-failure ** occurs after nRec is updated but before this connection writes ** anything else to the journal file (or commits/rolls back its ** transaction), then SQLite may become confused when doing the ** hot-journal rollback following recovery. It may roll back all ** of this connections data, then proceed to rolling back the old, ** out-of-date data that follows it. Database corruption. ** ** To work around this, if the journal file does appear to contain ** a valid header following Pager.journalOff, then write a 0x00 ** byte to the start of it to prevent it from being recognized. ** ** Variable iNextHdrOffset is set to the offset at which this ** problematic header will occur, if it exists. aMagic is used ** as a temporary buffer to inspect the first couple of bytes of ** the potential journal header. */ i64 iNextHdrOffset = journalHdrOffset(pPager); u8 aMagic[8]; rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset); if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){ static const u8 zerobyte = 0; rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset); } if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){ return rc; } /* 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. */ if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager))); IOTRACE(("JSYNC %p\n", pPager)) rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags); if( rc!=SQLITE_OK ) return rc; } IOTRACE(("JHDR %p %lld %d\n", pPager, iNRecOffset, 4)); rc = write32bits(pPager->jfd, iNRecOffset, pPager->nRec); if( rc!=SQLITE_OK ) return rc; } if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ PAGERTRACE(("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!=SQLITE_OK ) return rc; } } /* The journal file was just successfully synced. Set Pager.needSync ** to zero and clear the PGHDR_NEED_SYNC flag on all pagess. */ pPager->needSync = 0; pPager->journalStarted = 1; sqlite3PcacheClearSyncFlags(pPager->pPCache); } return SQLITE_OK; } /* ** The argument is the first in a linked list of dirty pages connected ** by the PgHdr.pDirty pointer. This function writes each one of the ** in-memory pages in the list to the database file. The argument may ** be NULL, representing an empty list. In this case this function is ** a no-op. ** ** The pager must hold at least a RESERVED lock when this function ** is called. Before writing anything to the database file, this lock ** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained, ** SQLITE_BUSY is returned and no data is written to the database file. ** ** If the pager is a temp-file pager and the actual file-system file ** is not yet open, it is created and opened before any data is ** written out. ** ** Once the lock has been upgraded and, if necessary, the file opened, ** the pages are written out to the database file in list order. Writing ** a page is skipped if it meets either of the following criteria: ** ** * The page number is greater than Pager.dbSize, or ** * The PGHDR_DONT_WRITE flag is set on the page. ** ** If writing out a page causes the database file to grow, Pager.dbFileSize ** is updated accordingly. If page 1 is written out, then the value cached ** in Pager.dbFileVers[] is updated to match the new value stored in ** the database file. ** ** If everything is successful, SQLITE_OK is returned. If an IO error ** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot ** be obtained, SQLITE_BUSY is returned. */ static int pager_write_pagelist(PgHdr *pList){ Pager *pPager; /* Pager object */ int rc; /* Return code */ 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 ** call is a no-op. ** ** 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. */ assert( pPager->state>=PAGER_RESERVED ); rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK); /* If the file is a temp-file has not yet been opened, open it now. It ** is not possible for rc to be other than SQLITE_OK if this branch ** is taken, as pager_wait_on_lock() is a no-op for temp-files. */ if( !isOpen(pPager->fd) ){ assert( pPager->tempFile && rc==SQLITE_OK ); rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags); } while( rc==SQLITE_OK && pList ){ Pgno pgno = pList->pgno; /* If there are dirty pages in the page cache with page numbers greater ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to ** make the file smaller (presumably by auto-vacuum code). Do not write ** any such pages to the file. ** ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag ** set (set by sqlite3PagerDontWrite()). */ if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){ i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */ char *pData = CODEC2(pPager, pList->pData, pgno, 6); /* Data to write */ /* Write out the page data. */ rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset); /* If page 1 was just written, update Pager.dbFileVers to match ** the value now stored in the database file. If writing this ** page caused the database file to grow, update dbFileSize. */ if( pgno==1 ){ memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers)); } if( pgno>pPager->dbFileSize ){ pPager->dbFileSize = pgno; } /* Update any backup objects copying the contents of this pager. */ sqlite3BackupUpdate(pPager->pBackup, pgno, (u8 *)pData); PAGERTRACE(("STORE %d page %d hash(%08x)\n", PAGERID(pPager), pgno, pager_pagehash(pList))); IOTRACE(("PGOUT %p %d\n", pPager, pgno)); PAGER_INCR(sqlite3_pager_writedb_count); PAGER_INCR(pPager->nWrite); }else{ PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno)); } #ifdef SQLITE_CHECK_PAGES pList->pageHash = pager_pagehash(pList); #endif pList = pList->pDirty; } return rc; } /* ** Append a record of the current state of page pPg to the sub-journal. ** It is the callers responsibility to use subjRequiresPage() to check ** that it is really required before calling this function. ** ** If successful, set the bit corresponding to pPg->pgno in the bitvecs ** for all open savepoints before returning. ** ** This function returns SQLITE_OK if everything is successful, an IO ** error code if the attempt to write to the sub-journal fails, or ** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint ** bitvec. */ static int subjournalPage(PgHdr *pPg){ int rc = SQLITE_OK; Pager *pPager = pPg->pPager; if( isOpen(pPager->sjfd) ){ void *pData = pPg->pData; i64 offset = pPager->nSubRec*(4+pPager->pageSize); char *pData2 = CODEC2(pPager, pData, pPg->pgno, 7); PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno)); assert( pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize ); rc = write32bits(pPager->sjfd, offset, pPg->pgno); if( rc==SQLITE_OK ){ rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4); } } if( rc==SQLITE_OK ){ pPager->nSubRec++; assert( pPager->nSavepoint>0 ); rc = addToSavepointBitvecs(pPager, pPg->pgno); testcase( rc!=SQLITE_OK ); } return rc; } /* ** This function is called by the pcache layer when it has reached some ** soft memory limit. The first argument is a pointer to a Pager object ** (cast as a void*). The pager is always 'purgeable' (not an in-memory ** database). The second argument is a reference to a page that is ** currently dirty but has no outstanding references. The page ** is always associated with the Pager object passed as the first ** argument. ** ** The job of this function is to make pPg clean by writing its contents ** out to the database file, if possible. This may involve syncing the ** journal file. ** ** If successful, sqlite3PcacheMakeClean() is called on the page and ** SQLITE_OK returned. If an IO error occurs while trying to make the ** page clean, the IO error code is returned. If the page cannot be ** made clean for some other reason, but no error occurs, then SQLITE_OK ** is returned by sqlite3PcacheMakeClean() is not called. */ static int pagerStress(void *p, PgHdr *pPg){ Pager *pPager = (Pager *)p; int rc = SQLITE_OK; assert( pPg->pPager==pPager ); assert( pPg->flags&PGHDR_DIRTY ); /* The doNotSync flag is set by the sqlite3PagerWrite() function while it ** is journalling a set of two or more database pages that are stored ** on the same disk sector. Syncing the journal is not allowed while ** this is happening as it is important that all members of such a ** set of pages are synced to disk together. So, if the page this function ** is trying to make clean will require a journal sync and the doNotSync ** flag is set, return without doing anything. The pcache layer will ** just have to go ahead and allocate a new page buffer instead of ** reusing pPg. ** ** Similarly, if the pager has already entered the error state, do not ** try to write the contents of pPg to disk. */ if( pPager->errCode || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC) ){ return SQLITE_OK; } /* Sync the journal file if required. */ 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 the page number of this page is larger than the current size of ** the database image, it may need to be written to the sub-journal. ** This is because the call to pager_write_pagelist() below will not ** actually write data to the file in this case. ** ** Consider the following sequence of events: ** ** BEGIN; ** ** ** SAVEPOINT sp; ** ** pagerStress(page X) ** ROLLBACK TO sp; ** ** If (X>Y), then when pagerStress is called page X will not be written ** out to the database file, but will be dropped from the cache. Then, ** following the "ROLLBACK TO sp" statement, reading page X will read ** data from the database file. This will be the copy of page X as it ** was when the transaction started, not as it was when "SAVEPOINT sp" ** was executed. ** ** The solution is to write the current data for page X into the ** sub-journal file now (if it is not already there), so that it will ** be restored to its current value when the "ROLLBACK TO sp" is ** executed. */ if( rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg) ){ rc = subjournalPage(pPg); } /* Write the contents of the page out to the database file. */ if( rc==SQLITE_OK ){ pPg->pDirty = 0; rc = pager_write_pagelist(pPg); } /* Mark the page as clean. */ if( rc==SQLITE_OK ){ PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno)); sqlite3PcacheMakeClean(pPg); } return pager_error(pPager, rc); } /* ** Allocate and initialize a new Pager object and put a pointer to it ** in *ppPager. The pager should eventually be freed by passing it ** to sqlite3PagerClose(). ** ** The zFilename argument is the path to the database file to open. ** If zFilename is NULL then a randomly-named temporary file is created ** and used as the file to be cached. Temporary files are be deleted ** automatically when they are 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. ** ** The nExtra parameter specifies the number of bytes of space allocated ** along with each page reference. This space is available to the user ** via the sqlite3PagerGetExtra() API. ** ** The flags argument is used to specify properties that affect the ** operation of the pager. It should be passed some bitwise combination ** of the PAGER_OMIT_JOURNAL and PAGER_NO_READLOCK flags. ** ** The vfsFlags parameter is a bitmask to pass to the flags parameter ** of the xOpen() method of the supplied VFS when opening files. ** ** If the pager object is allocated and the specified file opened ** successfully, SQLITE_OK is returned and *ppPager set to point to ** the new pager object. If an error occurs, *ppPager is set to NULL ** and error code returned. This function may return SQLITE_NOMEM ** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or ** various SQLITE_IO_XXX errors. */ int sqlite3PagerOpen( sqlite3_vfs *pVfs, /* The virtual file system to use */ Pager **ppPager, /* OUT: 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; /* Pager object to allocate and return */ int rc = SQLITE_OK; /* Return code */ int tempFile = 0; /* True for temp files (incl. in-memory files) */ int memDb = 0; /* True if this is an in-memory file */ int readOnly = 0; /* True if this is a read-only file */ int journalFileSize; /* Bytes to allocate for each journal fd */ char *zPathname = 0; /* Full path to database file */ int nPathname = 0; /* Number of bytes in zPathname */ int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */ int noReadlock = (flags & PAGER_NO_READLOCK)!=0; /* True to omit read-lock */ int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */ u16 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */ /* Figure out how much space is required for each journal file-handle ** (there are two of them, the main journal and the sub-journal). This ** is the maximum space required for an in-memory journal file handle ** and a regular journal file-handle. Note that a "regular journal-handle" ** may be a wrapper capable of caching the first portion of the journal ** file in memory to implement the atomic-write optimization (see ** source file journal.c). */ if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){ journalFileSize = ROUND8(sqlite3JournalSize(pVfs)); }else{ journalFileSize = ROUND8(sqlite3MemJournalSize()); } /* Set the output variable to NULL in case an error occurs. */ *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 { zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */ rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname); } nPathname = sqlite3Strlen30(zPathname); if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){ /* This branch is taken when the journal path required by ** the database being opened will be more than pVfs->mxPathname ** bytes in length. This means the database cannot be opened, ** as it will not be possible to open the journal file or even ** check for a hot-journal before reading. */ rc = SQLITE_CANTOPEN; } if( rc!=SQLITE_OK ){ sqlite3_free(zPathname); return rc; } } /* Allocate memory for the Pager structure, PCache object, the ** three file descriptors, the database file name and the journal ** file name. The layout in memory is as follows: ** ** Pager object (sizeof(Pager) bytes) ** PCache object (sqlite3PcacheSize() bytes) ** Database file handle (pVfs->szOsFile bytes) ** Sub-journal file handle (journalFileSize bytes) ** Main journal file handle (journalFileSize bytes) ** Database file name (nPathname+1 bytes) ** Journal file name (nPathname+8+1 bytes) */ pPtr = (u8 *)sqlite3MallocZero( ROUND8(sizeof(*pPager)) + /* Pager structure */ ROUND8(pcacheSize) + /* PCache object */ ROUND8(pVfs->szOsFile) + /* The main db file */ journalFileSize * 2 + /* The two journal files */ nPathname + 1 + /* zFilename */ nPathname + 8 + 1 /* zJournal */ ); assert( EIGHT_BYTE_ALIGNMENT(journalFileSize) ); if( !pPtr ){ sqlite3_free(zPathname); return SQLITE_NOMEM; } pPager = (Pager*)(pPtr); pPager->pPCache = (PCache*)(pPtr += ROUND8(sizeof(*pPager))); pPager->fd = (sqlite3_file*)(pPtr += ROUND8(pcacheSize)); pPager->sjfd = (sqlite3_file*)(pPtr += ROUND8(pVfs->szOsFile)); pPager->jfd = (sqlite3_file*)(pPtr += journalFileSize); pPager->zFilename = (char*)(pPtr += journalFileSize); assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) ); /* Fill in the Pager.zFilename and Pager.zJournal buffers, if required. */ if( zPathname ){ pPager->zJournal = (char*)(pPtr += nPathname + 1); memcpy(pPager->zFilename, zPathname, nPathname); memcpy(pPager->zJournal, zPathname, nPathname); memcpy(&pPager->zJournal[nPathname], "-journal", 8); sqlite3_free(zPathname); } pPager->pVfs = pVfs; pPager->vfsFlags = vfsFlags; /* Open the pager file. */ if( zFilename && zFilename[0] && !memDb ){ int fout = 0; /* VFS flags returned by xOpen() */ rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, 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 ){ setSectorSize(pPager); assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE); if( szPageDfltsectorSize ){ if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){ szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE; }else{ szPageDflt = (u16)pPager->sectorSize; } } #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 } }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; } /* The following call to PagerSetPagesize() serves to set the value of ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer. */ if( rc==SQLITE_OK ){ assert( pPager->memDb==0 ); rc = sqlite3PagerSetPagesize(pPager, &szPageDflt); testcase( rc!=SQLITE_OK ); } /* If an error occurred in either of the blocks above, free the ** Pager structure and close the file. */ if( rc!=SQLITE_OK ){ assert( !pPager->pTmpSpace ); sqlite3OsClose(pPager->fd); sqlite3_free(pPager); return rc; } /* Initialize the PCache object. */ nExtra = ROUND8(nExtra); sqlite3PcacheOpen(szPageDflt, nExtra, !memDb, !memDb?pagerStress:0, (void *)pPager, pPager->pPCache); PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename)); IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename)) pPager->useJournal = (u8)useJournal; pPager->noReadlock = (noReadlock && readOnly) ?1:0; /* pPager->stmtOpen = 0; */ /* pPager->stmtInUse = 0; */ /* pPager->nRef = 0; */ pPager->dbSizeValid = (u8)memDb; /* pPager->stmtSize = 0; */ /* pPager->stmtJSize = 0; */ /* pPager->nPage = 0; */ pPager->mxPgno = SQLITE_MAX_PAGE_COUNT; /* pPager->state = PAGER_UNLOCK; */ assert( pPager->state == (tempFile ? PAGER_EXCLUSIVE : PAGER_UNLOCK) ); /* pPager->errMask = 0; */ pPager->tempFile = (u8)tempFile; assert( tempFile==PAGER_LOCKINGMODE_NORMAL || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE ); assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 ); pPager->exclusiveMode = (u8)tempFile; pPager->changeCountDone = pPager->tempFile; pPager->memDb = (u8)memDb; pPager->readOnly = (u8)readOnly; /* pPager->needSync = 0; */ pPager->noSync = (pPager->tempFile || !useJournal) ?1:0; 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( isOpen(pPager->fd) || 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; } /* ** This function is called after transitioning from PAGER_UNLOCK to ** PAGER_SHARED state. It tests if there is a hot journal present in ** the file-system for the given pager. A hot journal is one that ** needs to be played back. According to this function, a hot-journal ** file exists if the following criteria are met: ** ** * The journal file exists in the file system, and ** * No process holds a RESERVED or greater lock on the database file, and ** * The database file itself is greater than 0 bytes in size, and ** * The first byte of the journal file exists and is not 0x00. ** ** 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. In this case the journal file is ** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK ** is returned. ** ** This routine does not check if there is a master journal filename ** at the end of the file. If there is, and that master journal file ** does not exist, then the journal file is not really hot. In this ** case this routine will return a false-positive. The pager_playback() ** routine will discover that the journal file is not really hot and ** will not roll it back. ** ** If a hot-journal file is found to exist, *pExists is set to 1 and ** SQLITE_OK returned. If no hot-journal file is present, *pExists is ** set to 0 and SQLITE_OK returned. If an IO error occurs while trying ** to determine whether or not a hot-journal file exists, the IO error ** code is returned and the value of *pExists is undefined. */ static int hasHotJournal(Pager *pPager, int *pExists){ sqlite3_vfs * const pVfs = pPager->pVfs; int rc; /* Return code */ int exists; /* True if a journal file is present */ assert( pPager!=0 ); assert( pPager->useJournal ); assert( isOpen(pPager->fd) ); assert( !isOpen(pPager->jfd) ); *pExists = 0; rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists); if( rc==SQLITE_OK && exists ){ int locked; /* True if some process holds a RESERVED lock */ rc = sqlite3OsCheckReservedLock(pPager->fd, &locked); if( rc==SQLITE_OK && !locked ){ int nPage; /* Check the size of the database file. If it consists of 0 pages, ** then delete the journal file. See the header comment above for ** the reasoning here. */ rc = sqlite3PagerPagecount(pPager, &nPage); if( rc==SQLITE_OK ){ if( nPage==0 ){ rc = sqlite3OsDelete(pVfs, pPager->zJournal, 0); }else{ /* The journal file exists and no other connection has a reserved ** or greater lock on the database file. Now check that there is ** at least one non-zero bytes at the start of the journal file. ** If there is, then we consider this journal to be hot. If not, ** it can be ignored. */ int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL; rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f); if( rc==SQLITE_OK ){ u8 first = 0; rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } sqlite3OsClose(pPager->jfd); *pExists = (first!=0); } } } } } return rc; } /* ** Read the content for page pPg out of the database file and into ** pPg->pData. A shared lock or greater must be held on the database ** file before this function is called. ** ** If page 1 is read, then the value of Pager.dbFileVers[] is set to ** the value read from the database file. ** ** If an IO error occurs, then the IO error is returned to the caller. ** Otherwise, SQLITE_OK is returned. */ static int readDbPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */ Pgno pgno = pPg->pgno; /* Page number to read */ int rc; /* Return code */ i64 iOffset; /* Byte offset of file to read from */ assert( pPager->state>=PAGER_SHARED && !MEMDB ); if( !isOpen(pPager->fd) ){ assert( pPager->tempFile ); memset(pPg->pData, 0, pPager->pageSize); return SQLITE_OK; } iOffset = (pgno-1)*(i64)pPager->pageSize; rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } if( pgno==1 ){ u8 *dbFileVers = &((u8*)pPg->pData)[24]; memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers)); } CODEC1(pPager, pPg->pData, pgno, 3); PAGER_INCR(sqlite3_pager_readdb_count); PAGER_INCR(pPager->nRead); IOTRACE(("PGIN %p %d\n", pPager, pgno)); PAGERTRACE(("FETCH %d page %d hash(%08x)\n", PAGERID(pPager), pgno, pager_pagehash(pPg))); return rc; } /* ** This function is called whenever the upper layer requests a database ** page is requested, before the cache is checked for a suitable page ** or any data is read from the database. It performs the following ** two functions: ** ** 1) If the pager is currently in PAGER_UNLOCK state (no lock held ** on the database file), then an attempt is made to obtain a ** SHARED lock on the database file. Immediately after obtaining ** the SHARED lock, the file-system is checked for a hot-journal, ** which is played back if present. Following any hot-journal ** rollback, the contents of the cache are validated by checking ** the 'change-counter' field of the database file header and ** discarded if they are found to be invalid. ** ** 2) If the pager is running in exclusive-mode, and there are currently ** no outstanding references to any pages, and is in the error state, ** then an attempt is made to clear the error state by discarding ** the contents of the page cache and rolling back any open journal ** file. ** ** If the operation described by (2) above is not attempted, and if the ** pager is in an error state other than SQLITE_FULL when this is called, ** the error state error code is returned. It is permitted to read the ** database when in SQLITE_FULL error state. ** ** Otherwise, if everything is successful, SQLITE_OK is returned. If an ** IO error occurs while locking the database, checking for a hot-journal ** file or rolling back a journal file, the IO error code is returned. */ static int pagerSharedLock(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ int isErrorReset = 0; /* True if recovering from error state */ /* If this database is opened for exclusive access, has no outstanding ** page references and is in an error-state, this is a 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( isOpen(pPager->jfd) ){ 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 * const pVfs = pPager->pVfs; int isHotJournal = 0; 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); } }else if( pPager->state==PAGER_UNLOCK ){ pPager->state = PAGER_SHARED; } 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 the ** hot-journal back. ** ** Because the intermediate RESERVED lock is not requested, any ** other process attempting to access the database file will get to ** this point in the code and fail to obtain its own EXCLUSIVE lock ** on the database file. */ if( pPager->statefd, 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( !isOpen(pPager->jfd) ){ 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 || isOpen(pPager->jfd) ); 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; } /* TODO: Why are these cleared here? Is it necessary? */ 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. Purge the cache before ** playing back the hot-journal so that we don't end up with ** an inconsistent cache. */ 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 ); } failed: if( rc!=SQLITE_OK ){ /* pager_unlock() is a no-op for exclusive mode and in-memory databases. */ pager_unlock(pPager); } return rc; } /* ** If the reference count has reached zero, rollback any active ** transaction and unlock the pager. ** ** Except, in locking_mode=EXCLUSIVE when there is nothing to in ** the rollback journal, the unlock is not performed and there is ** nothing to rollback, so this routine is a no-op. */ 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 reference to page number pgno in pager pPager (a page ** reference has type DbPage*). If the requested reference is ** successfully obtained, it is copied to *ppPage and SQLITE_OK returned. ** ** This function calls pagerSharedLock() to obtain a SHARED lock on ** the database file if such a lock or greater is not already held. ** This may cause hot-journal rollback or a cache purge. See comments ** above function pagerSharedLock() for details. ** ** If the requested page is already in the cache, it is returned. ** Otherwise, a new page object is allocated and populated with data ** read from the database file. In some cases, the pcache module may ** choose not to allocate a new page object and may reuse an existing ** object with no outstanding references. ** ** The extra data appended to a page is always initialized to zeros the ** first time a page is loaded into memory. If the page requested is ** already in the cache when this function is called, then the extra ** data is left as it was when the page object was last used. ** ** If the database image is smaller than the requested page or if a ** non-zero value is passed as the noContent parameter and the ** requested page is not already stored in the cache, then no ** actual disk read occurs. In this case the memory image of the ** page is initialized to all zeros. ** ** If noContent is true, it means that we do not care about the contents ** of the page. This occurs in two seperate scenarios: ** ** a) When reading a free-list leaf page from the database, and ** ** b) When a savepoint is being rolled back and we need to load ** a new page into the cache to populate with the data read ** from the savepoint journal. ** ** If noContent is true, then the data returned is zeroed instead of ** being read from the database. Additionally, the bits corresponding ** to pgno in Pager.pInJournal (bitvec of pages already written to the ** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open ** savepoints are set. This means if the page is made writable at any ** point in the future, using a call to sqlite3PagerWrite(), its contents ** will not be journaled. This saves IO. ** ** 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. */ 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( assert_pager_state(pPager) ); 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; } assert( pPg->pgno==pgno ); assert( pPg->pPager==pPager || pPg->pPager==0 ); 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; 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; } if( noContent ){ /* Failure to set the bits in the InJournal bit-vectors is benign. ** It merely means that we might do some extra work to journal a ** page that does not need to be journaled. Nevertheless, be sure ** to test the case where a malloc error occurs while trying to set ** a bit in a bit vector. */ sqlite3BeginBenignMalloc(); if( pgno<=pPager->dbOrigSize ){ TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno); testcase( rc==SQLITE_NOMEM ); } TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno); testcase( rc==SQLITE_NOMEM ); sqlite3EndBenignMalloc(); }else{ memset(pPg->pData, 0, pPager->pageSize); } IOTRACE(("ZERO %p %d\n", pPager, pgno)); }else{ assert( pPg->pPager==pPager ); rc = readDbPage(pPg); if( rc!=SQLITE_OK ){ pagerDropPage(pPg); return rc; } } #ifdef SQLITE_CHECK_PAGES pPg->pageHash = pager_pagehash(pPg); #endif }else{ /* The requested page is in the page cache. */ PAGER_INCR(pPager->nHit); } *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. Also, return 0 if the ** pager is in PAGER_UNLOCK state when this function is called, ** or if the pager is in an error state other than SQLITE_FULL. ** ** 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 reference. ** ** 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. */ void sqlite3PagerUnref(DbPage *pPg){ if( pPg ){ Pager *pPager = pPg->pPager; sqlite3PcacheRelease(pPg); pagerUnlockIfUnused(pPager); } } /* ** If the main journal file has already been opened, ensure that the ** sub-journal file is open too. If the main journal is not open, ** this function is a no-op. ** ** SQLITE_OK is returned if everything goes according to plan. ** An SQLITE_IOERR_XXX error code is returned if a call to ** sqlite3OsOpen() fails. */ static int openSubJournal(Pager *pPager){ int rc = SQLITE_OK; if( isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ){ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){ sqlite3MemJournalOpen(pPager->sjfd); }else{ rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL); } } return rc; } /* ** This function is called at the start of every write transaction. ** There must already be a RESERVED or EXCLUSIVE lock on the database ** file when this routine is called. ** ** Open the journal file for pager pPager and write a journal header ** to the start of it. If there are active savepoints, open the sub-journal ** as well. This function is only used when the journal file is being ** opened to write a rollback log for a transaction. It is not used ** when opening a hot journal file to roll it back. ** ** If the journal file is already open (as it may be in exclusive mode), ** then this function just writes a journal header to the start of the ** already open file. ** ** Whether or not the journal file is opened by this function, the ** Pager.pInJournal bitvec structure is allocated. ** ** Return SQLITE_OK if everything is successful. Otherwise, return ** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or ** an IO error code if opening or writing the journal file fails. */ static int pager_open_journal(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ sqlite3_vfs * const pVfs = pPager->pVfs; /* Local cache of vfs pointer */ assert( pPager->state>=PAGER_RESERVED ); assert( pPager->useJournal ); assert( pPager->pInJournal==0 ); /* If already in the error state, this function is a no-op. */ if( pPager->errCode ){ return pPager->errCode; } /* TODO: Is it really possible to get here with dbSizeValid==0? If not, ** the call to PagerPagecount() can be removed. */ testcase( pPager->dbSizeValid==0 ); sqlite3PagerPagecount(pPager, 0); pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize); if( pPager->pInJournal==0 ){ return SQLITE_NOMEM; } /* Open the journal file if it is not already open. */ if( !isOpen(pPager->jfd) ){ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){ sqlite3MemJournalOpen(pPager->jfd); }else{ const int flags = /* VFS flags to open journal file */ SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE| (pPager->tempFile ? (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL): (SQLITE_OPEN_MAIN_JOURNAL) ); #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 || isOpen(pPager->jfd) ); } /* Write the first journal header to the journal file and open ** the sub-journal if necessary. */ if( rc==SQLITE_OK ){ /* TODO: Check if all of these are really required. */ pPager->dbOrigSize = pPager->dbSize; pPager->journalStarted = 0; pPager->needSync = 0; pPager->nRec = 0; pPager->journalOff = 0; pPager->setMaster = 0; pPager->journalHdr = 0; rc = writeJournalHdr(pPager); } if( rc==SQLITE_OK && pPager->nSavepoint ){ rc = openSubJournal(pPager); } if( rc!=SQLITE_OK ){ sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; } return rc; } /* ** Begin a write-transaction on the specified pager object. If a ** write-transaction has already been opened, this function is a no-op. ** ** If the exFlag argument is false, then acquire at least a RESERVED ** lock on the database file. If exFlag is true, then acquire at least ** an EXCLUSIVE lock. If such a lock is already held, no locking ** functions need be called. ** ** If this is not a temporary or in-memory file and, the journal file is ** opened if it has not been already. For a temporary file, the opening ** of the journal file is deferred until there is an actual need to ** write to the journal. TODO: Why handle temporary files differently? ** ** If the journal file is opened (or if it is already open), then a ** journal-header is written to the start of it. */ int sqlite3PagerBegin(Pager *pPager, int exFlag){ int rc = SQLITE_OK; assert( pPager->state!=PAGER_UNLOCK ); if( pPager->state==PAGER_SHARED ){ assert( pPager->pInJournal==0 ); assert( !MEMDB && !pPager->tempFile ); /* Obtain a RESERVED lock on the database file. If the exFlag parameter ** is true, then immediately upgrade this to an EXCLUSIVE lock. The ** busy-handler callback can be used when upgrading to the EXCLUSIVE ** lock, but not when obtaining the RESERVED lock. */ 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 the required locks were successfully obtained, open the journal ** file and write the first journal-header to it. */ if( rc==SQLITE_OK && pPager->useJournal && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ rc = pager_open_journal(pPager); } }else if( isOpen(pPager->jfd) && 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->dbOrigSize==0 ); assert( pPager->pInJournal==0 ); rc = pager_open_journal(pPager); } PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager))); assert( !isOpen(pPager->jfd) || pPager->journalOff>0 || rc!=SQLITE_OK ); return rc; } /* ** Mark a single data page as writeable. The page is written into the ** main journal or sub-journal as required. If the page is written into ** one of the journals, the corresponding bit is set in the ** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs ** of any open savepoints as appropriate. */ 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); /* 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) && !subjRequiresPage(pPg) ){ 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(pPager, 0); if( rc!=SQLITE_OK ){ return rc; } assert( pPager->state>=PAGER_RESERVED ); if( !isOpen(pPager->jfd) && pPager->useJournal && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ rc = pager_open_journal(pPager); if( rc!=SQLITE_OK ) return rc; } 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) && isOpen(pPager->jfd) ){ if( pPg->pgno<=pPager->dbOrigSize ){ 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); PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n", PAGERID(pPager), pPg->pgno, ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg))); /* Even if an IO or diskfull error occurred while journalling the ** page in the block above, set the need-sync flag for the page. ** Otherwise, when the transaction is rolled back, the logic in ** playback_one_page() will think that the page needs to be restored ** in the database file. And if an IO error occurs while doing so, ** then corruption may follow. */ if( !pPager->noSync ){ pPg->flags |= PGHDR_NEED_SYNC; pPager->needSync = 1; } /* An error has occurred 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 ); rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno); testcase( rc==SQLITE_NOMEM ); assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); rc |= addToSavepointBitvecs(pPager, pPg->pgno); if( rc!=SQLITE_OK ){ assert( rc==SQLITE_NOMEM ); return rc; } }else{ if( !pPager->journalStarted && !pPager->noSync ){ pPg->flags |= PGHDR_NEED_SYNC; pPager->needSync = 1; } PAGERTRACE(("APPEND %d page %d needSync=%d\n", PAGERID(pPager), pPg->pgno, ((pPg->flags&PGHDR_NEED_SYNC)?1:0))); } } /* 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( subjRequiresPage(pPg) ){ rc = subjournalPage(pPg); } } /* Update the database size and return. */ assert( pPager->state>=PAGER_SHARED ); if( pPager->dbSizepgno ){ pPager->dbSize = pPg->pgno; } return rc; } /* ** Mark a data page as writeable. This routine must be called before ** making changes to a page. The caller must check the return value ** of this function and be careful not to change any page data unless ** this routine returns SQLITE_OK. ** ** 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. ** ** If an error occurs, SQLITE_NOMEM or an IO error code is returned ** as appropriate. Otherwise, SQLITE_OK. */ 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; /* Loop counter */ int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */ /* 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; iipgno || !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; assert(pPager->needSync); } sqlite3PagerUnref(pPage); } } }else if( (pPage = pager_lookup(pPager, pg))!=0 ){ if( pPage->flags&PGHDR_NEED_SYNC ){ needSync = 1; } sqlite3PagerUnref(pPage); } } /* If the PGHDR_NEED_SYNC 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; iiflags |= 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 can quadruple the speed of large ** DELETE operations. */ void sqlite3PagerDontWrite(PgHdr *pPg){ Pager *pPager = pPg->pPager; if( (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){ PAGERTRACE(("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 } } /* ** This routine is called to increment the value of the database file ** change-counter, stored as a 4-byte big-endian integer starting at ** byte offset 24 of the pager file. ** ** If the isDirect flag is zero, then this is done by calling ** sqlite3PagerWrite() on page 1, then modifying the contents of the ** page data. In this case the file will be updated when the current ** transaction is committed. ** ** The isDirect flag may only be non-zero if the library was compiled ** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case, ** if isDirect is non-zero, then the database file is updated directly ** by writing an updated version of page 1 using a call to the ** sqlite3OsWrite() function. */ static int pager_incr_changecounter(Pager *pPager, int isDirectMode){ int rc = SQLITE_OK; /* Declare and initialize constant integer 'isDirect'. If the ** atomic-write optimization is enabled in this build, then isDirect ** is initialized to the value passed as the isDirectMode parameter ** to this function. Otherwise, it is always set to zero. ** ** The idea is that if the atomic-write optimization is not ** enabled at compile time, the compiler can omit the tests of ** 'isDirect' below, as well as the block enclosed in the ** "if( isDirect )" condition. */ #ifndef SQLITE_ENABLE_ATOMIC_WRITE const int isDirect = 0; assert( isDirectMode==0 ); UNUSED_PARAMETER(isDirectMode); #else const int isDirect = isDirectMode; #endif assert( pPager->state>=PAGER_RESERVED ); if( !pPager->changeCountDone && pPager->dbSize>0 ){ PgHdr *pPgHdr; /* Reference to page 1 */ u32 change_counter; /* Initial value of change-counter field */ assert( !pPager->tempFile && isOpen(pPager->fd) ); /* Open page 1 of the file for writing. */ rc = sqlite3PagerGet(pPager, 1, &pPgHdr); assert( pPgHdr==0 || rc==SQLITE_OK ); /* If page one was fetched successfully, and this function is not ** operating in direct-mode, make page 1 writable. */ if( rc==SQLITE_OK && !isDirect ){ rc = sqlite3PagerWrite(pPgHdr); } if( rc==SQLITE_OK ){ /* 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); /* If running in direct mode, write the contents of page 1 to the file. */ if( isDirect ){ const void *zBuf = pPgHdr->pData; assert( pPager->dbFileSize>0 ); rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0); } /* If everything worked, set the changeCountDone flag. */ if( rc==SQLITE_OK ){ pPager->changeCountDone = 1; } } /* Release the page reference. */ sqlite3PagerUnref(pPgHdr); } return rc; } /* ** Sync the pager file to disk. This is a no-op for in-memory files ** or pages with the Pager.noSync flag set. ** ** If successful, or called on a pager for which it is a no-op, this ** function returns SQLITE_OK. Otherwise, an IO error code is returned. */ int sqlite3PagerSync(Pager *pPager){ int rc; /* Return code */ if( MEMDB || pPager->noSync ){ 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 database file change-counter is updated, ** * the journal is synced (unless the atomic-write optimization is used), ** * all dirty pages are written to the database file, ** * the database file is truncated (if required), and ** * the database file synced. ** ** The only thing that remains to commit the transaction is to finalize ** (delete, truncate or zero the first part of) the journal file (or ** delete the master journal file if specified). ** ** Note that if zMaster==NULL, this does not overwrite a previous value ** passed to an sqlite3PagerCommitPhaseOne() call. ** ** 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, /* Pager object */ const char *zMaster, /* If not NULL, the master journal name */ int noSync /* True to omit the xSync on the db file */ ){ int rc = SQLITE_OK; /* Return code */ if( pPager->errCode ){ return pPager->errCode; } PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", pPager->zFilename, zMaster, pPager->dbSize)); /* 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( MEMDB && pPager->dbModified ){ sqlite3BackupRestart(pPager->pBackup); }else if( pPager->state!=PAGER_SYNCED && pPager->dbModified ){ /* The following block updates the change-counter. Exactly how it ** does this depends on whether or not the atomic-update optimization ** was enabled at compile time, and if this transaction meets the ** runtime criteria to use the operation: ** ** * 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 was not enabled at compile time, then the ** pager_incr_changecounter() function is called to update the change ** counter in 'indirect-mode'. If the optimization is compiled in but ** is not applicable to this transaction, call sqlite3JournalCreate() ** to make sure the journal file has actually been created, then call ** pager_incr_changecounter() to update the change-counter in indirect ** mode. ** ** Otherwise, if the optimization is both enabled and applicable, ** then call pager_incr_changecounter() to update the change-counter ** in 'direct' mode. In this case the journal file will never be ** created for this transaction. */ #ifdef SQLITE_ENABLE_ATOMIC_WRITE PgHdr *pPg; assert( isOpen(pPager->jfd) || pPager->journalMode==PAGER_JOURNALMODE_OFF ); if( !zMaster && isOpen(pPager->jfd) && pPager->journalOff==jrnlBufferSize(pPager) && pPager->dbSize>=pPager->dbFileSize && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty) ){ /* Update the db file change counter via the direct-write method. 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. */ rc = pager_incr_changecounter(pPager, 1); }else{ rc = sqlite3JournalCreate(pPager->jfd); if( rc==SQLITE_OK ){ rc = pager_incr_changecounter(pPager, 0); } } #else rc = pager_incr_changecounter(pPager, 0); #endif if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* If this transaction has made the database smaller, then all pages ** being discarded by the truncation must be written to the journal ** file. This can only happen in auto-vacuum mode. ** ** Before reading the pages with page numbers larger than the ** current value of Pager.dbSize, set dbSize back to the value ** that it took at the start of the transaction. Otherwise, the ** calls to sqlite3PagerGet() return zeroed pages instead of ** reading data from the database file. */ #ifndef SQLITE_OMIT_AUTOVACUUM if( pPager->dbSizedbOrigSize && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ Pgno i; /* Iterator variable */ const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */ const Pgno dbSize = pPager->dbSize; /* Database image size */ pPager->dbSize = pPager->dbOrigSize; for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){ if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){ PgHdr *pPage; /* Page to journal */ rc = sqlite3PagerGet(pPager, i, &pPage); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; rc = sqlite3PagerWrite(pPage); sqlite3PagerUnref(pPage); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; } } pPager->dbSize = dbSize; } #endif /* Write the master journal name into the journal file. If a master ** journal file name has already been written to the journal file, ** or if zMaster is NULL (no master journal), then this call is a no-op. */ rc = writeMasterJournal(pPager, zMaster); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* Sync the journal file. If the atomic-update optimization is being ** used, this call will not create the journal file or perform any ** real IO. */ rc = syncJournal(pPager); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* Write all dirty pages to the database file. */ rc = pager_write_pagelist(sqlite3PcacheDirtyList(pPager->pPCache)); if( rc!=SQLITE_OK ){ assert( rc!=SQLITE_IOERR_BLOCKED ); goto commit_phase_one_exit; } sqlite3PcacheCleanAll(pPager->pPCache); /* If the file on disk is not the same size as the database image, ** then use pager_truncate to grow or shrink the file here. */ if( pPager->dbSize!=pPager->dbFileSize ){ Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager)); assert( pPager->state>=PAGER_EXCLUSIVE ); rc = pager_truncate(pPager, nNew); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; } /* Finally, sync the database file. */ if( !pPager->noSync && !noSync ){ rc = sqlite3OsSync(pPager->fd, pPager->sync_flags); } IOTRACE(("DBSYNC %p\n", pPager)) pPager->state = PAGER_SYNCED; } commit_phase_one_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; } /* ** When this function is called, the database file has been completely ** updated to reflect the changes made by the current transaction and ** synced to disk. The journal file still exists in the file-system ** though, and if a failure occurs at this point it will eventually ** be used as a hot-journal and the current transaction rolled back. ** ** This function finalizes the journal file, either by deleting, ** truncating or partially zeroing it, so that it cannot be used ** for hot-journal rollback. Once this is done the transaction is ** irrevocably committed. ** ** If an error occurs, an IO error code is returned and the pager ** moves into the error state. Otherwise, SQLITE_OK is returned. */ int sqlite3PagerCommitPhaseTwo(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ /* Do not proceed if the pager is already in the error state. */ if( pPager->errCode ){ return pPager->errCode; } /* This function should not be called if the pager is not in at least ** PAGER_RESERVED state. And indeed SQLite never does this. But it is ** nice to have this defensive block here anyway. */ if( NEVER(pPager->statedbModified==0 && pPager->exclusiveMode && pPager->journalMode==PAGER_JOURNALMODE_PERSIST ){ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ); return SQLITE_OK; } PAGERTRACE(("COMMIT %d\n", PAGERID(pPager))); assert( pPager->state==PAGER_SYNCED || MEMDB || !pPager->dbModified ); rc = pager_end_transaction(pPager, pPager->setMaster); return pager_error(pPager, rc); } /* ** Rollback all changes. The database falls back to PAGER_SHARED mode. ** ** This function performs two tasks: ** ** 1) It rolls back the journal file, restoring all database file and ** in-memory cache pages to the state they were in when the transaction ** was opened, and ** 2) It finalizes the journal file, so that it is not used for hot ** rollback at any point in the future. ** ** subject to the following qualifications: ** ** * If the journal file is not yet open when this function is called, ** then only (2) is performed. In this case there is no journal file ** to roll back. ** ** * If in an error state other than SQLITE_FULL, then task (1) is ** performed. If successful, task (2). Regardless of the outcome ** of either, the error state error code is returned to the caller ** (i.e. either SQLITE_IOERR or SQLITE_CORRUPT). ** ** * If the pager is in PAGER_RESERVED state, then attempt (1). Whether ** or not (1) is succussful, also attempt (2). If successful, return ** SQLITE_OK. Otherwise, enter the error state and return the first ** error code encountered. ** ** In this case there is no chance that the database was written to. ** So is safe to finalize the journal file even if the playback ** (operation 1) failed. However the pager must enter the error state ** as the contents of the in-memory cache are now suspect. ** ** * Finally, if in PAGER_EXCLUSIVE state, then attempt (1). Only ** attempt (2) if (1) is successful. Return SQLITE_OK if successful, ** otherwise enter the error state and return the error code from the ** failing operation. ** ** In this case the database file may have been written to. So if the ** playback operation did not succeed it would not be safe to finalize ** the journal file. It needs to be left in the file-system so that ** some other process can use it to restore the database state (by ** hot-journal rollback). */ int sqlite3PagerRollback(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager))); if( !pPager->dbModified || !isOpen(pPager->jfd) ){ 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. */ u8 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; } #endif /* ** Return true if this is an in-memory pager. */ int sqlite3PagerIsMemdb(Pager *pPager){ return MEMDB; } /* ** Check that there are at least nSavepoint savepoints open. If there are ** currently less than nSavepoints open, then open one or more savepoints ** to make up the difference. If the number of savepoints is already ** equal to nSavepoint, then this function is a no-op. ** ** If a memory allocation fails, SQLITE_NOMEM is returned. If an error ** occurs while opening the sub-journal file, then an IO error code is ** returned. Otherwise, SQLITE_OK. */ int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){ int rc = SQLITE_OK; /* Return code */ int nCurrent = pPager->nSavepoint; /* Current number of savepoints */ if( nSavepoint>nCurrent && pPager->useJournal ){ int ii; /* Iterator variable */ PagerSavepoint *aNew; /* New Pager.aSavepoint array */ /* Either there is no active journal or the sub-journal is open or ** the journal is always stored in memory */ assert( pPager->nSavepoint==0 || isOpen(pPager->sjfd) || pPager->journalMode==PAGER_JOURNALMODE_MEMORY ); /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM ** if the allocation fails. Otherwise, zero the new portion in case a ** malloc failure occurs while populating it in the for(...) loop below. */ aNew = (PagerSavepoint *)sqlite3Realloc( pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint ); if( !aNew ){ return SQLITE_NOMEM; } memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint)); pPager->aSavepoint = aNew; pPager->nSavepoint = nSavepoint; /* Populate the PagerSavepoint structures just allocated. */ for(ii=nCurrent; iidbSizeValid ); aNew[ii].nOrig = pPager->dbSize; if( isOpen(pPager->jfd) && pPager->journalOff>0 ){ aNew[ii].iOffset = pPager->journalOff; }else{ aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager); } aNew[ii].iSubRec = pPager->nSubRec; aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize); if( !aNew[ii].pInSavepoint ){ return SQLITE_NOMEM; } } /* Open the sub-journal, if it is not already opened. */ rc = openSubJournal(pPager); } return rc; } /* ** This function is called to rollback or release (commit) a savepoint. ** The savepoint to release or rollback need not be the most recently ** created savepoint. ** ** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE. ** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with ** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes ** that have occurred since the specified savepoint was created. ** ** The savepoint to rollback or release is identified by parameter ** iSavepoint. A value of 0 means to operate on the outermost savepoint ** (the first created). A value of (Pager.nSavepoint-1) means operate ** on the most recently created savepoint. If iSavepoint is greater than ** (Pager.nSavepoint-1), then this function is a no-op. ** ** If a negative value is passed to this function, then the current ** transaction is rolled back. This is different to calling ** sqlite3PagerRollback() because this function does not terminate ** the transaction or unlock the database, it just restores the ** contents of the database to its original state. ** ** In any case, all savepoints with an index greater than iSavepoint ** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE), ** then savepoint iSavepoint is also destroyed. ** ** This function may return SQLITE_NOMEM if a memory allocation fails, ** or an IO error code if an IO error occurs while rolling back a ** savepoint. If no errors occur, SQLITE_OK is returned. */ int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){ int rc = SQLITE_OK; assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK ); assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK ); if( iSavepointnSavepoint ){ int ii; /* Iterator variable */ int nNew; /* Number of remaining savepoints after this op. */ /* Figure out how many savepoints will still be active after this ** operation. Store this value in nNew. Then free resources associated ** with any savepoints that are destroyed by this operation. */ nNew = iSavepoint + (op==SAVEPOINT_ROLLBACK); for(ii=nNew; iinSavepoint; ii++){ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); } pPager->nSavepoint = nNew; /* If this is a rollback operation, playback the specified savepoint. ** If this is a temp-file, it is possible that the journal file has ** not yet been opened. In this case there have been no changes to ** the database file, so the playback operation can be skipped. */ if( op==SAVEPOINT_ROLLBACK && isOpen(pPager->jfd) ){ PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1]; rc = pagerPlaybackSavepoint(pPager, pSavepoint); assert(rc!=SQLITE_DONE); } /* If this is a release of the outermost savepoint, truncate ** the sub-journal to zero bytes in size. */ if( nNew==0 && op==SAVEPOINT_RELEASE && isOpen(pPager->sjfd) ){ assert( rc==SQLITE_OK ); rc = sqlite3OsTruncate(pPager->sjfd, 0); pPager->nSubRec = 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 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. ** ** This function may return SQLITE_NOMEM or an IO error code if an error ** occurs. Otherwise, it returns SQLITE_OK. */ int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){ PgHdr *pPgOld; /* The page being overwritten. */ Pgno needSyncPgno = 0; /* Old value of pPg->pgno, if sync is required */ int rc; /* Return code */ Pgno origPgno; /* The original page number */ assert( pPg->nRef>0 ); /* If the page being moved is dirty and has not been saved by the latest ** savepoint, then save the current contents of the page into the ** sub-journal now. This is required to handle the following scenario: ** ** BEGIN; ** ** SAVEPOINT one; ** ** ROLLBACK TO one; ** ** If page X were not written to the sub-journal here, it would not ** be possible to restore its contents when the "ROLLBACK TO one" ** statement were is processed. ** ** subjournalPage() may need to allocate space to store pPg->pgno into ** one or more savepoint bitvecs. This is the reason this function ** may return SQLITE_NOMEM. */ if( pPg->flags&PGHDR_DIRTY && subjRequiresPage(pPg) && SQLITE_OK!=(rc = subjournalPage(pPg)) ){ return rc; } PAGERTRACE(("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)) /* 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->dbOrigSize ); 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); sqlite3PcacheDrop(pPgOld); } origPgno = pPg->pgno; sqlite3PcacheMove(pPg, pgno); sqlite3PcacheMakeDirty(pPg); 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. */ PgHdr *pPgHdr; assert( pPager->needSync ); rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr); if( rc!=SQLITE_OK ){ if( pPager->pInJournal && needSyncPgno<=pPager->dbOrigSize ){ sqlite3BitvecClear(pPager->pInJournal, needSyncPgno); } return rc; } pPager->needSync = 1; assert( pPager->noSync==0 && !MEMDB ); pPgHdr->flags |= PGHDR_NEED_SYNC; sqlite3PcacheMakeDirty(pPgHdr); sqlite3PagerUnref(pPgHdr); } /* ** For an in-memory database, make sure the original page continues ** to exist, in case the transaction needs to roll back. We allocate ** the page now, instead of at rollback, because we can better deal ** with an out-of-memory error now. Ticket #3761. */ if( MEMDB ){ DbPage *pNew; rc = sqlite3PagerAcquire(pPager, origPgno, &pNew, 1); if( rc!=SQLITE_OK ) return rc; sqlite3PagerUnref(pNew); } 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 = (u8)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 ** PAGER_JOURNALMODE_MEMORY ** ** If the parameter is not _QUERY, then the journal_mode is set to the ** value specified if the change is allowed. The change is disallowed ** for the following reasons: ** ** * An in-memory database can only have its journal_mode set to _OFF ** or _MEMORY. ** ** * The journal mode may not be changed while a transaction is active. ** ** The returned indicate the current (possibly updated) journal-mode. */ int sqlite3PagerJournalMode(Pager *pPager, int eMode){ 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 && (!MEMDB || eMode==PAGER_JOURNALMODE_MEMORY || eMode==PAGER_JOURNALMODE_OFF) && !pPager->dbModified && (!isOpen(pPager->jfd) || 0==pPager->journalOff) ){ if( isOpen(pPager->jfd) ){ sqlite3OsClose(pPager->jfd); } pPager->journalMode = (u8)eMode; } return (int)pPager->journalMode; } /* ** Get/set the size-limit used for persistent journal files. ** ** Setting the size limit to -1 means no limit is enforced. ** An attempt to set a limit smaller than -1 is a no-op. */ i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){ if( iLimit>=-1 ){ pPager->journalSizeLimit = iLimit; } return pPager->journalSizeLimit; } /* ** Return a pointer to the pPager->pBackup variable. The backup module ** in backup.c maintains the content of this variable. This module ** uses it opaquely as an argument to sqlite3BackupRestart() and ** sqlite3BackupUpdate() only. */ sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){ return &pPager->pBackup; } #endif /* SQLITE_OMIT_DISKIO */