/* ** 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 1.159 2004/08/19 13:29:15 drh Exp $ */ #include "os.h" /* Must be first to enable large file support */ #include "sqliteInt.h" #include "pager.h" #include #include /* ** Macros for troubleshooting. Normally turned off */ #if 0 #define TRACE1(X) sqlite3DebugPrintf(X) #define TRACE2(X,Y) sqlite3DebugPrintf(X,Y) #define TRACE3(X,Y,Z) sqlite3DebugPrintf(X,Y,Z) #define TRACE4(X,Y,Z,W) sqlite3DebugPrintf(X,Y,Z,W) #else #define TRACE1(X) #define TRACE2(X,Y) #define TRACE3(X,Y,Z) #define TRACE4(X,Y,Z,W) #endif /* ** 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 the ** journal file and the transaction will be ** committed. ** ** The page cache comes up in PAGER_UNLOCK. The first time a ** sqlite3pager_get() 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 sqlite3pager_write() is called, the state transitions to ** PAGER_RESERVED. (Note that sqlite_page_write() can only be ** called on an outstanding page which means that the pager must ** be in PAGER_SHARED before it transitions to PAGER_RESERVED.) ** The transition to PAGER_EXCLUSIVE occurs when before any changes ** are made to the database file. After an sqlite3pager_rollback() ** or sqlite_pager_commit(), the state goes back to PAGER_SHARED. */ #define PAGER_UNLOCK 0 #define PAGER_SHARED 1 #define PAGER_RESERVED 2 #define PAGER_EXCLUSIVE 3 #define PAGER_SYNCED 4 /* ** Each in-memory image of a page begins with the following header. ** This header is only visible to this pager module. The client ** code that calls pager sees only the data that follows the header. ** ** Client code should call sqlite3pager_write() on a page prior to making ** any modifications to that page. The first time sqlite3pager_write() ** is called, the original page contents are written into the rollback ** journal and PgHdr.inJournal and PgHdr.needSync are set. Later, once ** the journal page has made it onto the disk surface, PgHdr.needSync ** is cleared. The modified page cannot be written back into the original ** database file until the journal pages has been synced to disk and the ** PgHdr.needSync has been cleared. ** ** The PgHdr.dirty flag is set when sqlite3pager_write() is called and ** is cleared again when the page content is written back to the original ** database file. */ typedef struct PgHdr PgHdr; struct PgHdr { Pager *pPager; /* The pager to which this page belongs */ Pgno pgno; /* The page number for this page */ PgHdr *pNextHash, *pPrevHash; /* Hash collision chain for PgHdr.pgno */ PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */ PgHdr *pNextAll; /* A list of all pages */ PgHdr *pNextStmt, *pPrevStmt; /* List of pages in the statement journal */ u8 inJournal; /* TRUE if has been written to journal */ u8 inStmt; /* TRUE if in the statement subjournal */ u8 dirty; /* TRUE if we need to write back changes */ u8 needSync; /* Sync journal before writing this page */ u8 alwaysRollback; /* Disable dont_rollback() for this page */ short int nRef; /* Number of users of this page */ PgHdr *pDirty; /* Dirty pages sorted by PgHdr.pgno */ /* pPager->pageSize bytes of page data follow this header */ /* Pager.nExtra bytes of local data follow the page data */ }; /* ** For an in-memory only database, some extra information is recorded about ** each page so that changes can be rolled back. (Journal files are not ** used for in-memory databases.) The following information is added to ** the end of every EXTRA block for in-memory databases. ** ** This information could have been added directly to the PgHdr structure. ** But then it would take up an extra 8 bytes of storage on every PgHdr ** even for disk-based databases. Splitting it out saves 8 bytes. This ** is only a savings of 0.8% but those percentages add up. */ typedef struct PgHistory PgHistory; struct PgHistory { u8 *pOrig; /* Original page text. Restore to this on a full rollback */ u8 *pStmt; /* Text as it was at the beginning of the current statement */ }; /* ** A macro used for invoking the codec if there is one */ #ifdef SQLITE_HAS_CODEC # define CODEC(P,D,N,X) if( P->xCodec ){ P->xCodec(P->pCodecArg,D,N,X); } #else # define CODEC(P,D,N,X) #endif /* ** Convert a pointer to a PgHdr into a pointer to its data ** and back again. */ #define PGHDR_TO_DATA(P) ((void*)(&(P)[1])) #define DATA_TO_PGHDR(D) (&((PgHdr*)(D))[-1]) #define PGHDR_TO_EXTRA(G,P) ((void*)&((char*)(&(G)[1]))[(P)->pageSize]) #define PGHDR_TO_HIST(P,PGR) \ ((PgHistory*)&((char*)(&(P)[1]))[(PGR)->pageSize+(PGR)->nExtra]) /* ** How big to make the hash table used for locating in-memory pages ** by page number. */ #define N_PG_HASH 2048 /* ** Hash a page number */ #define pager_hash(PN) ((PN)&(N_PG_HASH-1)) /* ** A open page cache is an instance of the following structure. */ struct Pager { char *zFilename; /* Name of the database file */ char *zJournal; /* Name of the journal file */ char *zDirectory; /* Directory hold database and journal files */ OsFile fd, jfd; /* File descriptors for database and journal */ OsFile stfd; /* File descriptor for the statement subjournal*/ int dbSize; /* Number of pages in the file */ int origDbSize; /* dbSize before the current change */ int stmtSize; /* Size of database (in pages) at stmt_begin() */ off_t stmtJSize; /* Size of journal at stmt_begin() */ int nRec; /* Number of pages written to the journal */ u32 cksumInit; /* Quasi-random value added to every checksum */ int stmtNRec; /* Number of records in stmt subjournal */ int nExtra; /* Add this many bytes to each in-memory page */ void (*xDestructor)(void*,int); /* Call this routine when freeing pages */ void (*xReiniter)(void*,int); /* Call this routine when reloading pages */ int pageSize; /* Number of bytes in a page */ int nPage; /* Total number of in-memory pages */ int nRef; /* Number of in-memory pages with PgHdr.nRef>0 */ int mxPage; /* Maximum number of pages to hold in cache */ int nHit, nMiss, nOvfl; /* Cache hits, missing, and LRU overflows */ void (*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */ void *pCodecArg; /* First argument to xCodec() */ u8 journalOpen; /* True if journal file descriptors is valid */ u8 journalStarted; /* True if header of journal is synced */ u8 useJournal; /* Use a rollback journal on this file */ u8 stmtOpen; /* True if the statement subjournal is open */ u8 stmtInUse; /* True we are in a statement subtransaction */ u8 stmtAutoopen; /* Open stmt journal when main journal is opened*/ u8 noSync; /* Do not sync the journal if true */ u8 fullSync; /* Do extra syncs of the journal for robustness */ u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */ u8 errMask; /* One of several kinds of errors */ u8 tempFile; /* zFilename is a temporary file */ u8 readOnly; /* True for a read-only database */ u8 needSync; /* True if an fsync() is needed on the journal */ u8 dirtyCache; /* True if cached pages have changed */ u8 alwaysRollback; /* Disable dont_rollback() for all pages */ u8 memDb; /* True to inhibit all file I/O */ u8 *aInJournal; /* One bit for each page in the database file */ u8 *aInStmt; /* One bit for each page in the database */ BusyHandler *pBusyHandler; /* Pointer to sqlite.busyHandler */ PgHdr *pFirst, *pLast; /* List of free pages */ PgHdr *pFirstSynced; /* First free page with PgHdr.needSync==0 */ PgHdr *pAll; /* List of all pages */ PgHdr *pStmt; /* List of pages in the statement subjournal */ PgHdr *aHash[N_PG_HASH]; /* Hash table to map page number to PgHdr */ off_t journalOff; /* Current byte offset in the journal file */ off_t journalHdr; /* Byte offset to previous journal header */ off_t stmtHdrOff; /* First journal header written this statement */ off_t stmtCksum; /* cksumInit when statement was started */ int sectorSize; /* Assumed sector size during rollback */ u8 setMaster; /* True if a m-j name has been written to jrnl */ }; /* ** These are bits that can be set in Pager.errMask. */ #define PAGER_ERR_FULL 0x01 /* a write() failed */ #define PAGER_ERR_MEM 0x02 /* malloc() failed */ #define PAGER_ERR_LOCK 0x04 /* error in the locking protocol */ #define PAGER_ERR_CORRUPT 0x08 /* database or journal corruption */ #define PAGER_ERR_DISK 0x10 /* general disk I/O error - bad hard drive? */ /* ** Journal files begin with the following magic string. The data ** was obtained from /dev/random. It is used only as a sanity check. ** ** Since version 2.8.0, the journal format contains additional sanity ** checking information. If the power fails while the journal is begin ** written, semi-random garbage data might appear in the journal ** file after power is restored. If an attempt is then made ** to roll the journal back, the database could be corrupted. The additional ** sanity checking data is an attempt to discover the garbage in the ** journal and ignore it. ** ** The sanity checking information for the new journal format consists ** of a 32-bit checksum on each page of data. The checksum covers both ** the page number and the pPager->pageSize bytes of data for the page. ** This cksum is initialized to a 32-bit random value that appears in the ** journal file right after the header. The random initializer is important, ** because garbage data that appears at the end of a journal is likely ** data that was once in other files that have now been deleted. If the ** garbage data came from an obsolete journal file, the checksums might ** be correct. But by initializing the checksum to random value which ** is different for every journal, we minimize that risk. */ static const unsigned char aJournalMagic[] = { 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7, }; /* ** The size of the header and of each page in the journal is determined ** by the following macros. */ #define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8) /* ** The journal header size for this pager. In the future, this could be ** set to some value read from the disk controller. The important ** characteristic is that it is the same size as a disk sector. */ #define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize) #define PAGER_SECTOR_SIZE 512 /* ** Page number PAGER_MJ_PGNO is never used in an SQLite database (it is ** reserved for working around a windows/posix incompatibility). It is ** used in the journal to signify that the remainder of the journal file ** is devoted to storing a master journal name - there are no more pages to ** roll back. See comments for function writeMasterJournal() for details. */ #define PAGER_MJ_PGNO(x) (PENDING_BYTE/((x)->pageSize)) /* ** Enable reference count tracking (for debugging) here: */ #ifdef SQLITE_TEST int pager3_refinfo_enable = 0; static void pager_refinfo(PgHdr *p){ static int cnt = 0; if( !pager3_refinfo_enable ) return; printf( "REFCNT: %4d addr=0x%08x nRef=%d\n", p->pgno, (int)PGHDR_TO_DATA(p), p->nRef ); cnt++; /* Something to set a breakpoint on */ } # define REFINFO(X) pager_refinfo(X) #else # define REFINFO(X) #endif /* ** 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(OsFile *fd, u32 *pRes){ u32 res; int rc; rc = sqlite3OsRead(fd, &res, sizeof(res)); if( rc==SQLITE_OK ){ unsigned char ac[4]; memcpy(ac, &res, 4); res = (ac[0]<<24) | (ac[1]<<16) | (ac[2]<<8) | ac[3]; } *pRes = res; return rc; } /* ** 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(OsFile *fd, u32 val){ unsigned char ac[4]; ac[0] = (val>>24) & 0xff; ac[1] = (val>>16) & 0xff; ac[2] = (val>>8) & 0xff; ac[3] = val & 0xff; return sqlite3OsWrite(fd, ac, 4); } /* ** Write the 32-bit integer 'val' into the page identified by page header ** 'p' at offset 'offset'. */ static void store32bits(u32 val, PgHdr *p, int offset){ unsigned char *ac; ac = &((unsigned char*)PGHDR_TO_DATA(p))[offset]; ac[0] = (val>>24) & 0xff; ac[1] = (val>>16) & 0xff; ac[2] = (val>>8) & 0xff; ac[3] = val & 0xff; } /* ** Read a 32-bit integer at offset 'offset' from the page identified by ** page header 'p'. */ static u32 retrieve32bits(PgHdr *p, int offset){ unsigned char *ac; ac = &((unsigned char*)PGHDR_TO_DATA(p))[offset]; return (ac[0]<<24) | (ac[1]<<16) | (ac[2]<<8) | ac[3]; } /* ** Convert the bits in the pPager->errMask into an approprate ** return code. */ static int pager_errcode(Pager *pPager){ int rc = SQLITE_OK; if( pPager->errMask & PAGER_ERR_LOCK ) rc = SQLITE_PROTOCOL; if( pPager->errMask & PAGER_ERR_DISK ) rc = SQLITE_IOERR; if( pPager->errMask & PAGER_ERR_FULL ) rc = SQLITE_FULL; if( pPager->errMask & PAGER_ERR_MEM ) rc = SQLITE_NOMEM; if( pPager->errMask & PAGER_ERR_CORRUPT ) rc = SQLITE_CORRUPT; return rc; } /* ** When this is called the journal file for pager pPager must be open. ** The master journal file name is read from the end of the file and ** written into memory obtained from sqliteMalloc(). *pzMaster is ** set to point at the memory and SQLITE_OK returned. The caller must ** sqliteFree() *pzMaster. ** ** If no master journal file name is present *pzMaster is set to 0 and ** SQLITE_OK returned. */ static int readMasterJournal(OsFile *pJrnl, char **pzMaster){ int rc; u32 len; off_t szJ; u32 cksum; int i; unsigned char aMagic[8]; /* A buffer to hold the magic header */ *pzMaster = 0; rc = sqlite3OsFileSize(pJrnl, &szJ); if( rc!=SQLITE_OK || szJ<16 ) return rc; rc = sqlite3OsSeek(pJrnl, szJ-16); if( rc!=SQLITE_OK ) return rc; rc = read32bits(pJrnl, &len); if( rc!=SQLITE_OK ) return rc; rc = read32bits(pJrnl, &cksum); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsRead(pJrnl, aMagic, 8); if( rc!=SQLITE_OK || memcmp(aMagic, aJournalMagic, 8) ) return rc; rc = sqlite3OsSeek(pJrnl, szJ-16-len); if( rc!=SQLITE_OK ) return rc; *pzMaster = (char *)sqliteMalloc(len+1); if( !*pzMaster ){ return SQLITE_NOMEM; } rc = sqlite3OsRead(pJrnl, *pzMaster, len); if( rc!=SQLITE_OK ){ sqliteFree(*pzMaster); *pzMaster = 0; return rc; } /* See if the checksum matches the master journal name */ for(i=0; ijournalOff; 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)journalOff = offset; return sqlite3OsSeek(&pPager->jfd, pPager->journalOff); } /* ** 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. ** ** Followed by (JOURNAL_HDR_SZ - 24) bytes of unused space. */ static int writeJournalHdr(Pager *pPager){ int rc = seekJournalHdr(pPager); if( rc ) return rc; pPager->journalHdr = pPager->journalOff; if( pPager->stmtHdrOff==0 ){ pPager->stmtHdrOff = pPager->journalHdr; } pPager->journalOff += JOURNAL_HDR_SZ(pPager); /* FIX ME: ** ** Possibly for a pager not in no-sync mode, the journal magic should not ** be written until nRec is filled in as part of next syncJournal(). ** ** Actually maybe the whole journal header should be delayed until that ** point. Think about this. */ rc = sqlite3OsWrite(&pPager->jfd, aJournalMagic, sizeof(aJournalMagic)); if( rc==SQLITE_OK ){ /* The nRec Field. 0xFFFFFFFF for no-sync journals. */ rc = write32bits(&pPager->jfd, pPager->noSync ? 0xffffffff : 0); } if( rc==SQLITE_OK ){ /* The random check-hash initialiser */ sqlite3Randomness(sizeof(pPager->cksumInit), &pPager->cksumInit); rc = write32bits(&pPager->jfd, pPager->cksumInit); } if( rc==SQLITE_OK ){ /* The initial database size */ rc = write32bits(&pPager->jfd, pPager->dbSize); } if( rc==SQLITE_OK ){ /* The assumed sector size for this process */ rc = write32bits(&pPager->jfd, pPager->sectorSize); } /* The journal header has been written successfully. Seek the journal ** file descriptor to the end of the journal header sector. */ if( rc==SQLITE_OK ){ sqlite3OsSeek(&pPager->jfd, pPager->journalOff-1); rc = sqlite3OsWrite(&pPager->jfd, "\000", 1); } return rc; } /* ** The journal file must be open when this is called. A journal header file ** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal ** file. See comments above function writeJournalHdr() for a description of ** the journal header format. ** ** If the header is read successfully, *nRec is set to the number of ** page records following this header and *dbSize is set to the size of the ** database before the transaction began, in pages. Also, pPager->cksumInit ** is set to the value read from the journal header. SQLITE_OK is returned ** in this case. ** ** If the journal header file appears to be corrupted, SQLITE_DONE is ** returned and *nRec and *dbSize are not set. If JOURNAL_HDR_SZ bytes ** cannot be read from the journal file an error code is returned. */ static int readJournalHdr( Pager *pPager, off_t journalSize, u32 *pNRec, u32 *pDbSize ){ int rc; unsigned char aMagic[8]; /* A buffer to hold the magic header */ rc = seekJournalHdr(pPager); if( rc ) return rc; if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){ return SQLITE_DONE; } rc = sqlite3OsRead(&pPager->jfd, aMagic, sizeof(aMagic)); if( rc ) return rc; if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){ return SQLITE_DONE; } rc = read32bits(&pPager->jfd, pNRec); if( rc ) return rc; rc = read32bits(&pPager->jfd, &pPager->cksumInit); if( rc ) return rc; rc = read32bits(&pPager->jfd, pDbSize); if( rc ) return rc; /* Update the assumed sector-size to match the value used by ** the process that created this journal. If this journal was ** created by a process other than this one, then this routine ** is being called from within pager_playback(). The local value ** of Pager.sectorSize is restored at the end of that routine. */ rc = read32bits(&pPager->jfd, (u32 *)&pPager->sectorSize); if( rc ) return rc; pPager->journalOff += JOURNAL_HDR_SZ(pPager); rc = sqlite3OsSeek(&pPager->jfd, pPager->journalOff); 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: length of master journal name. ** + 4 bytes: N ** + 4 bytes: Master journal name checksum. ** + 8 bytes: aJournalMagic[]. ** ** The master journal page checksum is the sum of the bytes in the master ** journal name. */ static int writeMasterJournal(Pager *pPager, const char *zMaster){ int rc; int len; int i; u32 cksum = 0; if( !zMaster || pPager->setMaster) return SQLITE_OK; pPager->setMaster = 1; len = strlen(zMaster); for(i=0; ifullSync ){ rc = seekJournalHdr(pPager); if( rc!=SQLITE_OK ) return rc; } pPager->journalOff += (len+20); rc = write32bits(&pPager->jfd, PAGER_MJ_PGNO(pPager)); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsWrite(&pPager->jfd, zMaster, len); if( rc!=SQLITE_OK ) return rc; rc = write32bits(&pPager->jfd, len); if( rc!=SQLITE_OK ) return rc; rc = write32bits(&pPager->jfd, cksum); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsWrite(&pPager->jfd, aJournalMagic, sizeof(aJournalMagic)); return rc; } /* ** Add or remove a page from the list of all pages that are in the ** statement journal. ** ** The Pager keeps a separate list of pages that are currently in ** the statement journal. This helps the sqlite3pager_stmt_commit() ** routine run MUCH faster for the common case where there are many ** pages in memory but only a few are in the statement journal. */ static void page_add_to_stmt_list(PgHdr *pPg){ Pager *pPager = pPg->pPager; if( pPg->inStmt ) return; assert( pPg->pPrevStmt==0 && pPg->pNextStmt==0 ); pPg->pPrevStmt = 0; if( pPager->pStmt ){ pPager->pStmt->pPrevStmt = pPg; } pPg->pNextStmt = pPager->pStmt; pPager->pStmt = pPg; pPg->inStmt = 1; } static void page_remove_from_stmt_list(PgHdr *pPg){ if( !pPg->inStmt ) return; if( pPg->pPrevStmt ){ assert( pPg->pPrevStmt->pNextStmt==pPg ); pPg->pPrevStmt->pNextStmt = pPg->pNextStmt; }else{ assert( pPg->pPager->pStmt==pPg ); pPg->pPager->pStmt = pPg->pNextStmt; } if( pPg->pNextStmt ){ assert( pPg->pNextStmt->pPrevStmt==pPg ); pPg->pNextStmt->pPrevStmt = pPg->pPrevStmt; } pPg->pNextStmt = 0; pPg->pPrevStmt = 0; pPg->inStmt = 0; } /* ** Find a page in the hash table given its page number. Return ** a pointer to the page or NULL if not found. */ static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){ PgHdr *p = pPager->aHash[pager_hash(pgno)]; while( p && p->pgno!=pgno ){ p = p->pNextHash; } return p; } /* ** Unlock the database and clear the in-memory cache. This routine ** sets the state of the pager back to what it was when it was first ** opened. Any outstanding pages are invalidated and subsequent attempts ** to access those pages will likely result in a coredump. */ static void pager_reset(Pager *pPager){ PgHdr *pPg, *pNext; for(pPg=pPager->pAll; pPg; pPg=pNext){ pNext = pPg->pNextAll; sqliteFree(pPg); } pPager->pFirst = 0; pPager->pFirstSynced = 0; pPager->pLast = 0; pPager->pAll = 0; memset(pPager->aHash, 0, sizeof(pPager->aHash)); pPager->nPage = 0; if( pPager->state>=PAGER_RESERVED ){ sqlite3pager_rollback(pPager); } sqlite3OsUnlock(&pPager->fd, NO_LOCK); pPager->state = PAGER_UNLOCK; pPager->dbSize = -1; pPager->nRef = 0; assert( pPager->journalOpen==0 ); } /* ** When this routine is called, the pager has the journal file open and ** a RESERVED or EXCLUSIVE lock on the database. This routine releases ** the database lock and acquires a SHARED lock in its place. The journal ** file is deleted and closed. ** ** TODO: Consider keeping the journal file open for temporary databases. ** This might give a performance improvement on windows where opening ** a file is an expensive operation. */ static int pager_unwritelock(Pager *pPager){ PgHdr *pPg; assert( !pPager->memDb ); if( pPager->statestmtOpen ){ sqlite3OsClose(&pPager->stfd); pPager->stmtOpen = 0; } if( pPager->journalOpen ){ sqlite3OsClose(&pPager->jfd); pPager->journalOpen = 0; sqlite3OsDelete(pPager->zJournal); sqliteFree( pPager->aInJournal ); pPager->aInJournal = 0; for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ pPg->inJournal = 0; pPg->dirty = 0; pPg->needSync = 0; } pPager->dirtyCache = 0; pPager->nRec = 0; }else{ assert( pPager->dirtyCache==0 || pPager->useJournal==0 ); } sqlite3OsUnlock(&pPager->fd, SHARED_LOCK); pPager->state = PAGER_SHARED; pPager->origDbSize = 0; pPager->setMaster = 0; return SQLITE_OK; } /* ** Compute and return a checksum for the page of data. ** ** This is not a real checksum. It is really just the sum of the ** random initial value and the page number. We experimented with ** a checksum of the entire data, but that was found to be too slow. ** ** Note that the page number is stored at the beginning of data and ** the checksum is stored at the end. This is important. If journal ** corruption occurs due to a power failure, the most likely scenario ** is that one end or the other of the record will be changed. It is ** much less likely that the two ends of the journal record will be ** correct and the middle be corrupt. Thus, this "checksum" scheme, ** though fast and simple, catches the mostly likely kind of corruption. ** ** FIX ME: Consider adding every 200th (or so) byte of the data to the ** checksum. That way if a single page spans 3 or more disk sectors and ** only the middle sector is corrupt, we will still have a reasonable ** chance of failing the checksum and thus detecting the problem. */ static u32 pager_cksum(Pager *pPager, Pgno pgno, const char *aData){ u32 cksum = pPager->cksumInit; int i = pPager->pageSize-200; while( i>0 ){ cksum += aData[i]; i -= 200; } return cksum; } /* ** Read a single page from the journal file opened on file descriptor ** jfd. Playback this one page. ** ** If useCksum==0 it means this journal does not use checksums. Checksums ** are not used in statement journals because statement journals do not ** need to survive power failures. */ static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int useCksum){ 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[SQLITE_MAX_PAGE_SIZE]; /* Temp storage for a page */ rc = read32bits(jfd, &pgno); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsRead(jfd, &aData, pPager->pageSize); if( rc!=SQLITE_OK ) return rc; pPager->journalOff += pPager->pageSize + 4; /* Sanity checking on the page. This is more important that I originally ** thought. If a power failure occurs while the journal is being written, ** it could cause invalid data to be written into the journal. We need to ** detect this invalid data (with high probability) and ignore it. */ if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){ return SQLITE_DONE; } if( pgno>(unsigned)pPager->dbSize ){ return SQLITE_OK; } if( useCksum ){ rc = read32bits(jfd, &cksum); if( rc ) return rc; pPager->journalOff += 4; if( pager_cksum(pPager, pgno, aData)!=cksum ){ return SQLITE_DONE; } } assert( pPager->state==PAGER_RESERVED || pPager->state>=PAGER_EXCLUSIVE ); /* If the pager is in RESERVED state, then there must be a copy of this ** page in the pager cache. In this case just update the pager cache, ** not the database file. The page is left marked dirty in this case. ** ** If in EXCLUSIVE state, then we update the pager cache if it exists ** and the main file. The page is then marked not dirty. */ pPg = pager_lookup(pPager, pgno); assert( pPager->state>=PAGER_EXCLUSIVE || pPg ); TRACE3("PLAYBACK %d page %d\n", pPager->fd.h, pgno); if( pPager->state>=PAGER_EXCLUSIVE ){ sqlite3OsSeek(&pPager->fd, (pgno-1)*(off_t)pPager->pageSize); rc = sqlite3OsWrite(&pPager->fd, aData, pPager->pageSize); } if( pPg ){ /* No page should ever be 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. */ void *pData; assert( pPg->nRef==0 || pPg->pgno==1 ); pData = PGHDR_TO_DATA(pPg); memcpy(pData, aData, pPager->pageSize); if( pPager->xDestructor ){ /*** FIX ME: Should this be xReinit? ***/ pPager->xDestructor(pData, pPager->pageSize); } if( pPager->state>=PAGER_EXCLUSIVE ){ pPg->dirty = 0; pPg->needSync = 0; } CODEC(pPager, pData, pPg->pgno, 3); } return rc; } /* ** Parameter zMaster is the name of a master journal file. A single journal ** file that referred to the master journal file has just been rolled back. ** This routine checks if it is possible to delete the master journal file, ** and does so if it is. ** ** The master journal file contains the names of all child journals. ** To tell if a master journal can be deleted, check to each of the ** children. If all children are either missing or do not refer to ** a different master journal, then this master journal can be deleted. */ static int pager_delmaster(const char *zMaster){ int rc; int master_open = 0; OsFile master; char *zMasterJournal = 0; /* Contents of master journal file */ off_t nMasterJournal; /* Size of master journal file */ /* Open the master journal file exclusively in case some other process ** is running this routine also. Not that it makes too much difference. */ memset(&master, 0, sizeof(master)); rc = sqlite3OsOpenReadOnly(zMaster, &master); if( rc!=SQLITE_OK ) goto delmaster_out; master_open = 1; rc = sqlite3OsFileSize(&master, &nMasterJournal); if( rc!=SQLITE_OK ) goto delmaster_out; if( nMasterJournal>0 ){ char *zJournal; char *zMasterPtr = 0; /* Load the entire master journal file into space obtained from ** sqliteMalloc() and pointed to by zMasterJournal. */ zMasterJournal = (char *)sqliteMalloc(nMasterJournal); if( !zMasterJournal ){ rc = SQLITE_NOMEM; goto delmaster_out; } rc = sqlite3OsRead(&master, zMasterJournal, nMasterJournal); if( rc!=SQLITE_OK ) goto delmaster_out; zJournal = zMasterJournal; while( (zJournal-zMasterJournal)pAll; pPg; pPg=pPg->pNextAll){ char zBuf[SQLITE_MAX_PAGE_SIZE]; if( !pPg->dirty ) continue; if( (int)pPg->pgno <= pPager->origDbSize ){ sqlite3OsSeek(&pPager->fd, pPager->pageSize*(off_t)(pPg->pgno-1)); rc = sqlite3OsRead(&pPager->fd, zBuf, pPager->pageSize); TRACE3("REFETCH %d page %d\n", pPager->fd.h, pPg->pgno); if( rc ) break; CODEC(pPager, zBuf, pPg->pgno, 2); }else{ memset(zBuf, 0, pPager->pageSize); } if( pPg->nRef==0 || memcmp(zBuf, PGHDR_TO_DATA(pPg), pPager->pageSize) ){ memcpy(PGHDR_TO_DATA(pPg), zBuf, pPager->pageSize); if( pPager->xReiniter ){ pPager->xReiniter(PGHDR_TO_DATA(pPg), pPager->pageSize); }else{ memset(PGHDR_TO_EXTRA(pPg, pPager), 0, pPager->nExtra); } } pPg->needSync = 0; pPg->dirty = 0; } return rc; } /* ** Truncate the main file of the given pager to the number of pages ** indicated. */ static int pager_truncate(Pager *pPager, int nPage){ return sqlite3OsTruncate(&pPager->fd, pPager->pageSize*(off_t)nPage); } /* ** 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 integer which is the number of bytes in the master journal ** name. The value may be zero (indicate that there is no master ** journal.) ** (6) 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. ** (7) 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 6 items above. ** Each entry in the journal is an instance of the 7th item. ** ** Call the value from the second bullet "nRec". nRec is the number of ** valid page entries in the journal. In most cases, you can compute the ** value of nRec from the size of the journal file. But if a power ** failure occurred while the journal was being written, it could be the ** case that the size of the journal file had already been increased but ** the extra entries had not yet made it safely to disk. In such a case, ** the value of nRec computed from the file size would be too large. For ** that reason, we always use the nRec value in the header. ** ** If the nRec value is 0xffffffff it means that nRec should be computed ** from the file size. This value is used when the user selects the ** no-sync option for the journal. A power failure could lead to corruption ** in this case. But for things like temporary table (which will be ** deleted when the power is restored) we don't care. ** ** If the file opened as the journal file is not a well-formed ** journal file then all pages up to the first corrupted page are rolled ** back (or no pages if the journal header is corrupted). The journal file ** is then deleted and SQLITE_OK returned, just as if no corruption had ** been encountered. ** ** If an I/O or malloc() error occurs, the journal-file is not deleted ** and an error code is returned. */ static int pager_playback(Pager *pPager){ off_t szJ; /* Size of the journal file in bytes */ u32 nRec; /* Number of Records in the journal */ int i; /* Loop counter */ Pgno mxPg = 0; /* Size of the original file in pages */ int rc; /* Result code of a subroutine */ char *zMaster = 0; /* Name of master journal file if any */ /* Figure out how many records are in the journal. Abort early if ** the journal is empty. */ assert( pPager->journalOpen ); rc = sqlite3OsFileSize(&pPager->jfd, &szJ); if( rc!=SQLITE_OK ){ 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. */ rc = readMasterJournal(&pPager->jfd, &zMaster); assert( rc!=SQLITE_DONE ); if( rc!=SQLITE_OK || (zMaster && !sqlite3OsFileExists(zMaster)) ){ sqliteFree(zMaster); zMaster = 0; if( rc==SQLITE_DONE ) rc = SQLITE_OK; goto end_playback; } sqlite3OsSeek(&pPager->jfd, 0); pPager->journalOff = 0; /* This loop terminates either when the readJournalHdr() call returns ** SQLITE_DONE or an IO error occurs. */ while( 1 ){ /* Read the next journal header from the journal file. If there are ** not enough bytes left in the journal file for a complete header, or ** it is corrupted, then a process must of failed while writing it. ** This indicates nothing more needs to be rolled back. */ rc = readJournalHdr(pPager, szJ, &nRec, &mxPg); if( rc!=SQLITE_OK ){ if( rc==SQLITE_DONE ){ rc = SQLITE_OK; } goto end_playback; } /* If nRec is 0xffffffff, then this journal was created by a process ** working in no-sync mode. This means that the rest of the journal ** file consists of pages, there are no more journal headers. Compute ** the value of nRec based on this assumption. */ if( nRec==0xffffffff ){ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ); nRec = (szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager); } /* If this is the first header read from the journal, truncate the ** database file back to it's original size. */ if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){ assert( pPager->origDbSize==0 || pPager->origDbSize==mxPg ); rc = pager_truncate(pPager, mxPg); if( rc!=SQLITE_OK ){ goto end_playback; } pPager->dbSize = mxPg; } /* rc = sqlite3OsSeek(&pPager->jfd, JOURNAL_HDR_SZ(pPager)); */ if( rc!=SQLITE_OK ) goto end_playback; /* Copy original pages out of the journal and back into the database file. */ for(i=0; ijfd, 1); if( rc!=SQLITE_OK ){ if( rc==SQLITE_DONE ){ rc = SQLITE_OK; pPager->journalOff = szJ; break; }else{ goto end_playback; } } } } /* Pages that have been written to the journal but never synced ** where not restored by the loop above. We have to restore those ** pages by reading them back from the original database. */ assert( rc==SQLITE_OK ); pager_reload_cache(pPager); end_playback: if( rc==SQLITE_OK ){ rc = pager_unwritelock(pPager); } if( zMaster ){ /* If there was a master journal and this routine will return true, ** see if it is possible to delete the master journal. If errors ** occur during this process, ignore them. */ if( rc==SQLITE_OK ){ pager_delmaster(zMaster); } sqliteFree(zMaster); } /* The Pager.sectorSize variable may have been updated while rolling ** back a journal created by a process with a different PAGER_SECTOR_SIZE ** value. Reset it to the correct value for this process. */ pPager->sectorSize = PAGER_SECTOR_SIZE; return rc; } /* ** Playback the statement journal. ** ** This is similar to playing back the transaction journal but with ** a few extra twists. ** ** (1) The number of pages in the database file at the start of ** the statement is stored in pPager->stmtSize, not in the ** journal file itself. ** ** (2) In addition to playing back the statement journal, also ** playback all pages of the transaction journal beginning ** at offset pPager->stmtJSize. */ static int pager_stmt_playback(Pager *pPager){ off_t szJ; /* Size of the full journal */ off_t hdrOff; int nRec; /* Number of Records */ int i; /* Loop counter */ int rc; szJ = pPager->journalOff; #ifndef NDEBUG { off_t os_szJ; rc = sqlite3OsFileSize(&pPager->jfd, &os_szJ); if( rc!=SQLITE_OK ) return rc; assert( szJ==os_szJ ); } #endif /* Set hdrOff to be the offset to the first journal header written ** this statement transaction, or the end of the file if no journal ** header was written. */ hdrOff = pPager->stmtHdrOff; assert( pPager->fullSync || !hdrOff ); if( !hdrOff ){ hdrOff = szJ; } /* Truncate the database back to its original size. */ rc = pager_truncate(pPager, pPager->stmtSize); pPager->dbSize = pPager->stmtSize; /* Figure out how many records are in the statement journal. */ assert( pPager->stmtInUse && pPager->journalOpen ); sqlite3OsSeek(&pPager->stfd, 0); nRec = pPager->stmtNRec; /* Copy original pages out of the statement journal and back into the ** database file. Note that the statement journal omits checksums from ** each record since power-failure recovery is not important to statement ** journals. */ for(i=nRec-1; i>=0; i--){ rc = pager_playback_one_page(pPager, &pPager->stfd, 0); assert( rc!=SQLITE_DONE ); if( rc!=SQLITE_OK ) goto end_stmt_playback; } /* Now roll some pages back from the transaction journal. Pager.stmtJSize ** was the size of the journal file when this statement was started, so ** everything after that needs to be rolled back, either into the ** database, the memory cache, or both. ** ** If it is not zero, then Pager.stmtHdrOff is the offset to the start ** of the first journal header written during this statement transaction. */ rc = sqlite3OsSeek(&pPager->jfd, pPager->stmtJSize); if( rc!=SQLITE_OK ){ goto end_stmt_playback; } pPager->journalOff = pPager->stmtJSize; pPager->cksumInit = pPager->stmtCksum; assert( JOURNAL_HDR_SZ(pPager)<(pPager->pageSize+8) ); while( pPager->journalOff <= (hdrOff-(pPager->pageSize+8)) ){ rc = pager_playback_one_page(pPager, &pPager->jfd, 1); assert( rc!=SQLITE_DONE ); if( rc!=SQLITE_OK ) goto end_stmt_playback; } while( pPager->journalOff < szJ ){ u32 nRec; u32 dummy; rc = readJournalHdr(pPager, szJ, &nRec, &dummy); if( rc!=SQLITE_OK ){ assert( rc!=SQLITE_DONE ); goto end_stmt_playback; } if( nRec==0 ){ nRec = (szJ - pPager->journalOff) / (pPager->pageSize+8); } for(i=nRec-1; i>=0 && pPager->journalOff < szJ; i--){ rc = pager_playback_one_page(pPager, &pPager->jfd, 1); assert( rc!=SQLITE_DONE ); if( rc!=SQLITE_OK ) goto end_stmt_playback; } } pPager->journalOff = szJ; end_stmt_playback: if( rc!=SQLITE_OK ){ pPager->errMask |= PAGER_ERR_CORRUPT; rc = SQLITE_CORRUPT; }else{ pPager->journalOff = szJ; /* pager_reload_cache(pPager); */ } return rc; } /* ** Change the maximum number of in-memory pages that are allowed. ** ** The maximum number is the absolute value of the mxPage parameter. ** If mxPage is negative, the noSync flag is also set. noSync bypasses ** calls to sqlite3OsSync(). The pager runs much faster with noSync on, ** but if the operating system crashes or there is an abrupt power ** failure, the database file might be left in an inconsistent and ** unrepairable state. */ void sqlite3pager_set_cachesize(Pager *pPager, int mxPage){ if( mxPage>=0 ){ pPager->noSync = pPager->tempFile; if( pPager->noSync ) pPager->needSync = 0; }else{ pPager->noSync = 1; mxPage = -mxPage; } if( mxPage>10 ){ pPager->mxPage = mxPage; }else{ pPager->mxPage = 10; } } /* ** 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. */ void sqlite3pager_set_safety_level(Pager *pPager, int level){ pPager->noSync = level==1 || pPager->tempFile; pPager->fullSync = level==3 && !pPager->tempFile; if( pPager->noSync ) pPager->needSync = 0; } /* ** Open a temporary file. Write the name of the file into zName ** (zName must be at least SQLITE_TEMPNAME_SIZE bytes long.) Write ** the file descriptor into *fd. Return SQLITE_OK on success or some ** other error code if we fail. ** ** The OS will automatically delete the temporary file when it is ** closed. */ static int sqlite3pager_opentemp(char *zFile, OsFile *fd){ int cnt = 8; int rc; do{ cnt--; sqlite3OsTempFileName(zFile); rc = sqlite3OsOpenExclusive(zFile, fd, 1); }while( cnt>0 && rc!=SQLITE_OK && rc!=SQLITE_NOMEM ); return rc; } /* ** Create a new page cache and put a pointer to the page cache in *ppPager. ** The file to be cached need not exist. The file is not locked until ** the first call to sqlite3pager_get() and is only held open until the ** last page is released using sqlite3pager_unref(). ** ** If zFilename is NULL then a randomly-named temporary file is created ** and used as the file to be cached. The file will be deleted ** automatically when it is closed. ** ** If zFilename is ":memory:" then all information is held in cache. ** It is never written to disk. This can be used to implement an ** in-memory database. */ int sqlite3pager_open( Pager **ppPager, /* Return the Pager structure here */ const char *zFilename, /* Name of the database file to open */ int nExtra, /* Extra bytes append to each in-memory page */ int useJournal /* TRUE to use a rollback journal on this file */ ){ Pager *pPager; char *zFullPathname = 0; int nameLen; OsFile fd; int rc = SQLITE_OK; int i; int tempFile = 0; int memDb = 0; int readOnly = 0; char zTemp[SQLITE_TEMPNAME_SIZE]; *ppPager = 0; memset(&fd, 0, sizeof(fd)); if( sqlite3_malloc_failed ){ return SQLITE_NOMEM; } if( zFilename && zFilename[0] ){ if( strcmp(zFilename,":memory:")==0 ){ memDb = 1; zFullPathname = sqliteStrDup(""); rc = SQLITE_OK; }else{ zFullPathname = sqlite3OsFullPathname(zFilename); if( zFullPathname ){ rc = sqlite3OsOpenReadWrite(zFullPathname, &fd, &readOnly); } } }else{ rc = sqlite3pager_opentemp(zTemp, &fd); zFilename = zTemp; zFullPathname = sqlite3OsFullPathname(zFilename); if( rc==SQLITE_OK ){ tempFile = 1; } } if( !zFullPathname ){ sqlite3OsClose(&fd); return SQLITE_NOMEM; } if( rc!=SQLITE_OK ){ sqlite3OsClose(&fd); sqliteFree(zFullPathname); return rc; } nameLen = strlen(zFullPathname); pPager = sqliteMalloc( sizeof(*pPager) + nameLen*3 + 30 ); if( pPager==0 ){ sqlite3OsClose(&fd); sqliteFree(zFullPathname); return SQLITE_NOMEM; } TRACE3("OPEN %d %s\n", fd.h, zFullPathname); pPager->zFilename = (char*)&pPager[1]; pPager->zDirectory = &pPager->zFilename[nameLen+1]; pPager->zJournal = &pPager->zDirectory[nameLen+1]; strcpy(pPager->zFilename, zFullPathname); strcpy(pPager->zDirectory, zFullPathname); for(i=nameLen; i>0 && pPager->zDirectory[i-1]!='/'; i--){} if( i>0 ) pPager->zDirectory[i-1] = 0; strcpy(pPager->zJournal, zFullPathname); sqliteFree(zFullPathname); strcpy(&pPager->zJournal[nameLen], "-journal"); pPager->fd = fd; #if OS_UNIX pPager->fd.pPager = pPager; #endif pPager->journalOpen = 0; pPager->useJournal = useJournal && !memDb; pPager->stmtOpen = 0; pPager->stmtInUse = 0; pPager->nRef = 0; pPager->dbSize = memDb-1; pPager->pageSize = SQLITE_DEFAULT_PAGE_SIZE; pPager->stmtSize = 0; pPager->stmtJSize = 0; pPager->nPage = 0; pPager->mxPage = 100; pPager->state = PAGER_UNLOCK; pPager->errMask = 0; pPager->tempFile = tempFile; pPager->memDb = memDb; pPager->readOnly = readOnly; pPager->needSync = 0; pPager->noSync = pPager->tempFile || !useJournal; pPager->fullSync = (pPager->noSync?0:1); pPager->pFirst = 0; pPager->pFirstSynced = 0; pPager->pLast = 0; pPager->nExtra = nExtra; pPager->sectorSize = PAGER_SECTOR_SIZE; pPager->pBusyHandler = 0; memset(pPager->aHash, 0, sizeof(pPager->aHash)); *ppPager = pPager; return SQLITE_OK; } /* ** Set the busy handler function. */ void sqlite3pager_set_busyhandler(Pager *pPager, BusyHandler *pBusyHandler){ pPager->pBusyHandler = pBusyHandler; } /* ** Set the destructor for this pager. If not NULL, the destructor is called ** when the reference count on each page reaches zero. The destructor can ** be used to clean up information in the extra segment appended to each page. ** ** The destructor is not called as a result sqlite3pager_close(). ** Destructors are only called by sqlite3pager_unref(). */ void sqlite3pager_set_destructor(Pager *pPager, void (*xDesc)(void*,int)){ pPager->xDestructor = xDesc; } /* ** Set the reinitializer for this pager. If not NULL, the reinitializer ** is called when the content of a page in cache is restored to its original ** value as a result of a rollback. The callback gives higher-level code ** an opportunity to restore the EXTRA section to agree with the restored ** page data. */ void sqlite3pager_set_reiniter(Pager *pPager, void (*xReinit)(void*,int)){ pPager->xReiniter = xReinit; } /* ** Set the page size. ** ** The page size must only be changed when the cache is empty. */ void sqlite3pager_set_pagesize(Pager *pPager, int pageSize){ assert( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE ); pPager->pageSize = pageSize; } /* ** Read the first N bytes from the beginning of the file into memory ** that pDest points to. No error checking is done. */ void sqlite3pager_read_fileheader(Pager *pPager, int N, unsigned char *pDest){ memset(pDest, 0, N); if( pPager->memDb==0 ){ sqlite3OsSeek(&pPager->fd, 0); sqlite3OsRead(&pPager->fd, pDest, N); } } /* ** Return the total number of pages in the disk file associated with ** pPager. */ int sqlite3pager_pagecount(Pager *pPager){ off_t n; assert( pPager!=0 ); if( pPager->dbSize>=0 ){ return pPager->dbSize; } if( sqlite3OsFileSize(&pPager->fd, &n)!=SQLITE_OK ){ pPager->errMask |= PAGER_ERR_DISK; return 0; } n /= pPager->pageSize; if( !pPager->memDb && n==PENDING_BYTE/pPager->pageSize ){ n++; } if( pPager->state!=PAGER_UNLOCK ){ pPager->dbSize = n; } return n; } /* ** Forward declaration */ static int syncJournal(Pager*); /* ** Unlink a page from the free list (the list of all pages where nRef==0) ** and from its hash collision chain. */ static void unlinkPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; /* Keep the pFirstSynced pointer pointing at the first synchronized page */ if( pPg==pPager->pFirstSynced ){ PgHdr *p = pPg->pNextFree; while( p && p->needSync ){ p = p->pNextFree; } pPager->pFirstSynced = p; } /* Unlink from the freelist */ if( pPg->pPrevFree ){ pPg->pPrevFree->pNextFree = pPg->pNextFree; }else{ assert( pPager->pFirst==pPg ); pPager->pFirst = pPg->pNextFree; } if( pPg->pNextFree ){ pPg->pNextFree->pPrevFree = pPg->pPrevFree; }else{ assert( pPager->pLast==pPg ); pPager->pLast = pPg->pPrevFree; } pPg->pNextFree = pPg->pPrevFree = 0; /* Unlink from the pgno hash table */ if( pPg->pNextHash ){ pPg->pNextHash->pPrevHash = pPg->pPrevHash; } if( pPg->pPrevHash ){ pPg->pPrevHash->pNextHash = pPg->pNextHash; }else{ int h = pager_hash(pPg->pgno); assert( pPager->aHash[h]==pPg ); pPager->aHash[h] = pPg->pNextHash; } pPg->pNextHash = pPg->pPrevHash = 0; } /* ** This routine is used to truncate an in-memory database. Delete ** all pages whose pgno is larger than pPager->dbSize and is unreferenced. ** Referenced pages larger than pPager->dbSize are zeroed. */ static void memoryTruncate(Pager *pPager){ PgHdr *pPg; PgHdr **ppPg; int dbSize = pPager->dbSize; ppPg = &pPager->pAll; while( (pPg = *ppPg)!=0 ){ if( pPg->pgno<=dbSize ){ ppPg = &pPg->pNextAll; }else if( pPg->nRef>0 ){ memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize); ppPg = &pPg->pNextAll; }else{ *ppPg = pPg->pNextAll; unlinkPage(pPg); sqliteFree(pPg); pPager->nPage--; } } } /* ** Truncate the file to the number of pages specified. */ int sqlite3pager_truncate(Pager *pPager, Pgno nPage){ int rc; sqlite3pager_pagecount(pPager); if( pPager->errMask!=0 ){ rc = pager_errcode(pPager); return rc; } if( nPage>=(unsigned)pPager->dbSize ){ return SQLITE_OK; } if( pPager->memDb ){ pPager->dbSize = nPage; memoryTruncate(pPager); return SQLITE_OK; } rc = syncJournal(pPager); if( rc!=SQLITE_OK ){ return rc; } rc = pager_truncate(pPager, nPage); if( rc==SQLITE_OK ){ pPager->dbSize = nPage; } return rc; } /* ** Shutdown the page cache. Free all memory and close all files. ** ** If a transaction was in progress when this routine is called, that ** transaction is rolled back. All outstanding pages are invalidated ** and their memory is freed. Any attempt to use a page associated ** with this page cache after this function returns will likely ** result in a coredump. */ int sqlite3pager_close(Pager *pPager){ PgHdr *pPg, *pNext; switch( pPager->state ){ case PAGER_RESERVED: case PAGER_SYNCED: case PAGER_EXCLUSIVE: { sqlite3pager_rollback(pPager); if( !pPager->memDb ){ sqlite3OsUnlock(&pPager->fd, NO_LOCK); } assert( pPager->journalOpen==0 ); break; } case PAGER_SHARED: { if( !pPager->memDb ){ sqlite3OsUnlock(&pPager->fd, NO_LOCK); } break; } default: { /* Do nothing */ break; } } for(pPg=pPager->pAll; pPg; pPg=pNext){ #ifndef NDEBUG if( pPager->memDb ){ PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager); assert( !pPg->alwaysRollback ); assert( !pHist->pOrig ); assert( !pHist->pStmt ); } #endif pNext = pPg->pNextAll; sqliteFree(pPg); } TRACE2("CLOSE %d\n", pPager->fd.h); sqlite3OsClose(&pPager->fd); assert( pPager->journalOpen==0 ); /* Temp files are automatically deleted by the OS ** if( pPager->tempFile ){ ** sqlite3OsDelete(pPager->zFilename); ** } */ if( pPager->zFilename!=(char*)&pPager[1] ){ assert( 0 ); /* Cannot happen */ sqliteFree(pPager->zFilename); sqliteFree(pPager->zJournal); sqliteFree(pPager->zDirectory); } sqliteFree(pPager); return SQLITE_OK; } /* ** Return the page number for the given page data. */ Pgno sqlite3pager_pagenumber(void *pData){ PgHdr *p = DATA_TO_PGHDR(pData); return p->pgno; } /* ** The page_ref() function increments the reference count for a page. ** If the page is currently on the freelist (the reference count is zero) then ** remove it from the freelist. ** ** For non-test systems, page_ref() is a macro that calls _page_ref() ** online of the reference count is zero. For test systems, page_ref() ** is a real function so that we can set breakpoints and trace it. */ static void _page_ref(PgHdr *pPg){ if( pPg->nRef==0 ){ /* The page is currently on the freelist. Remove it. */ if( pPg==pPg->pPager->pFirstSynced ){ PgHdr *p = pPg->pNextFree; while( p && p->needSync ){ p = p->pNextFree; } pPg->pPager->pFirstSynced = p; } if( pPg->pPrevFree ){ pPg->pPrevFree->pNextFree = pPg->pNextFree; }else{ pPg->pPager->pFirst = pPg->pNextFree; } if( pPg->pNextFree ){ pPg->pNextFree->pPrevFree = pPg->pPrevFree; }else{ pPg->pPager->pLast = pPg->pPrevFree; } pPg->pPager->nRef++; } pPg->nRef++; REFINFO(pPg); } #ifdef SQLITE_TEST static void page_ref(PgHdr *pPg){ if( pPg->nRef==0 ){ _page_ref(pPg); }else{ pPg->nRef++; REFINFO(pPg); } } #else # define page_ref(P) ((P)->nRef==0?_page_ref(P):(void)(P)->nRef++) #endif /* ** Increment the reference count for a page. The input pointer is ** a reference to the page data. */ int sqlite3pager_ref(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); page_ref(pPg); return SQLITE_OK; } /* ** Sync the journal. In other words, make sure all the pages that have ** been written to the journal have actually reached the surface of the ** disk. It is not safe to modify the original database file until after ** the journal has been synced. If the original database is modified before ** the journal is synced and a power failure occurs, the unsynced journal ** data would be lost and we would be unable to completely rollback the ** database changes. Database corruption would occur. ** ** This routine also updates the nRec field in the header of the journal. ** (See comments on the pager_playback() routine for additional information.) ** If the sync mode is FULL, two syncs will occur. First the whole journal ** is synced, then the nRec field is updated, then a second sync occurs. ** ** For temporary databases, we do not care if we are able to rollback ** after a power failure, so sync occurs. ** ** This routine clears the needSync field of every page current held in ** memory. */ static int syncJournal(Pager *pPager){ PgHdr *pPg; int rc = SQLITE_OK; /* Sync the journal before modifying the main database ** (assuming there is a journal and it needs to be synced.) */ if( pPager->needSync ){ if( !pPager->tempFile ){ assert( pPager->journalOpen ); /* assert( !pPager->noSync ); // noSync might be set if synchronous ** was turned off after the transaction was started. Ticket #615 */ #ifndef NDEBUG { /* Make sure the pPager->nRec counter we are keeping agrees ** with the nRec computed from the size of the journal file. */ off_t jSz; rc = sqlite3OsFileSize(&pPager->jfd, &jSz); if( rc!=0 ) return rc; assert( pPager->journalOff==jSz ); } #endif { /* 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. */ if( pPager->fullSync ){ TRACE2("SYNC journal of %d\n", pPager->fd.h); rc = sqlite3OsSync(&pPager->jfd); if( rc!=0 ) return rc; } sqlite3OsSeek(&pPager->jfd, pPager->journalHdr + sizeof(aJournalMagic)); rc = write32bits(&pPager->jfd, pPager->nRec); if( rc ) return rc; sqlite3OsSeek(&pPager->jfd, pPager->journalOff); } TRACE2("SYNC journal of %d\n", pPager->fd.h); rc = sqlite3OsSync(&pPager->jfd); if( rc!=0 ) return rc; pPager->journalStarted = 1; } pPager->needSync = 0; /* Erase the needSync flag from every page. */ for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ pPg->needSync = 0; } pPager->pFirstSynced = pPager->pFirst; } #ifndef NDEBUG /* If the Pager.needSync flag is clear then the PgHdr.needSync ** flag must also be clear for all pages. Verify that this ** invariant is true. */ else{ for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ assert( pPg->needSync==0 ); } assert( pPager->pFirstSynced==pPager->pFirst ); } #endif return rc; } /* ** Given a list of pages (connected by the PgHdr.pDirty pointer) write ** every one of those pages out to the database file and mark them all ** as clean. */ static int pager_write_pagelist(PgHdr *pList){ Pager *pPager; int rc; int busy = 1; if( pList==0 ) return SQLITE_OK; pPager = pList->pPager; /* At this point there may be either a RESERVED or EXCLUSIVE lock on the ** database file. If there is already an EXCLUSIVE lock, the following ** calls to sqlite3OsLock() are no-ops. ** ** Moving the lock from RESERVED to EXCLUSIVE actually involves going ** through an intermediate state PENDING. A PENDING lock prevents new ** readers from attaching to the database but is unsufficient for us to ** write. The idea of a PENDING lock is to prevent new readers from ** coming in while we wait for existing readers to clear. ** ** While the pager is in the RESERVED state, the original database file ** is unchanged and we can rollback without having to playback the ** journal into the original database file. Once we transition to ** EXCLUSIVE, it means the database file has been changed and any rollback ** will require a journal playback. */ do { rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK); }while( rc==SQLITE_BUSY && pPager->pBusyHandler && pPager->pBusyHandler->xFunc && pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++) ); if( rc!=SQLITE_OK ){ return rc; } pPager->state = PAGER_EXCLUSIVE; while( pList ){ assert( pList->dirty ); sqlite3OsSeek(&pPager->fd, (pList->pgno-1)*(off_t)pPager->pageSize); CODEC(pPager, PGHDR_TO_DATA(pList), pList->pgno, 6); TRACE3("STORE %d page %d\n", pPager->fd.h, pList->pgno); rc = sqlite3OsWrite(&pPager->fd, PGHDR_TO_DATA(pList), pPager->pageSize); CODEC(pPager, PGHDR_TO_DATA(pList), pList->pgno, 0); if( rc ) return rc; pList->dirty = 0; pList = pList->pDirty; } return SQLITE_OK; } /* ** Collect every dirty page into a dirty list and ** return a pointer to the head of that list. All pages are ** collected even if they are still in use. */ static PgHdr *pager_get_all_dirty_pages(Pager *pPager){ PgHdr *p, *pList; pList = 0; for(p=pPager->pAll; p; p=p->pNextAll){ if( p->dirty ){ p->pDirty = pList; pList = p; } } return pList; } /* ** Acquire a page. ** ** A read lock on the disk file is obtained when the first page is acquired. ** This read lock is dropped when the last page is released. ** ** A _get works for any page number greater than 0. If the database ** file is smaller than the requested page, then no actual disk ** read occurs and the memory image of the page is initialized to ** all zeros. The extra data appended to a page is always initialized ** to zeros the first time a page is loaded into memory. ** ** The acquisition might fail for several reasons. In all cases, ** an appropriate error code is returned and *ppPage is set to NULL. ** ** See also sqlite3pager_lookup(). 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 sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){ PgHdr *pPg; int rc; /* Make sure we have not hit any critical errors. */ assert( pPager!=0 ); assert( pgno!=0 ); *ppPage = 0; if( pPager->errMask & ~(PAGER_ERR_FULL) ){ return pager_errcode(pPager); } /* If this is the first page accessed, then get a SHARED lock ** on the database file. */ if( pPager->nRef==0 && !pPager->memDb ){ int busy = 1; do { rc = sqlite3OsLock(&pPager->fd, SHARED_LOCK); }while( rc==SQLITE_BUSY && pPager->pBusyHandler && pPager->pBusyHandler->xFunc && pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++) ); if( rc!=SQLITE_OK ){ return rc; } pPager->state = PAGER_SHARED; /* 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( pPager->useJournal && sqlite3OsFileExists(pPager->zJournal) && !sqlite3OsCheckReservedLock(&pPager->fd) ){ int rc; /* Get an EXCLUSIVE lock on the database file. At this point it is ** important that a RESERVED lock is not obtained on the way to the ** EXCLUSIVE lock. If it were, another process might open the ** database file, detect the RESERVED lock, and conclude that the ** database is safe to read while this process is still rolling it ** back. ** ** Because the intermediate RESERVED lock is not requested, the ** second process will get to this point in the code and fail to ** obtain it's own EXCLUSIVE lock on the database file. */ rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK); if( rc!=SQLITE_OK ){ sqlite3OsUnlock(&pPager->fd, NO_LOCK); pPager->state = PAGER_UNLOCK; return rc; } pPager->state = PAGER_EXCLUSIVE; /* Open the journal for reading only. Return SQLITE_BUSY if ** we are unable to open the journal file. ** ** The journal file does not need to be locked itself. The ** journal file is never open unless the main database file holds ** a write lock, so there is never any chance of two or more ** processes opening the journal at the same time. */ rc = sqlite3OsOpenReadOnly(pPager->zJournal, &pPager->jfd); if( rc!=SQLITE_OK ){ sqlite3OsUnlock(&pPager->fd, NO_LOCK); pPager->state = PAGER_UNLOCK; return SQLITE_BUSY; } pPager->journalOpen = 1; pPager->journalStarted = 0; pPager->journalOff = 0; pPager->setMaster = 0; pPager->journalHdr = 0; /* Playback and delete the journal. Drop the database write ** lock and reacquire the read lock. */ rc = pager_playback(pPager); if( rc!=SQLITE_OK ){ return rc; } } pPg = 0; }else{ /* Search for page in cache */ pPg = pager_lookup(pPager, pgno); if( pPager->memDb && pPager->state==PAGER_UNLOCK ){ pPager->state = PAGER_SHARED; } } if( pPg==0 ){ /* The requested page is not in the page cache. */ int h; pPager->nMiss++; if( pPager->nPagemxPage || pPager->pFirst==0 || pPager->memDb ){ /* Create a new page */ pPg = sqliteMallocRaw( sizeof(*pPg) + pPager->pageSize + sizeof(u32) + pPager->nExtra + pPager->memDb*sizeof(PgHistory) ); if( pPg==0 ){ if( !pPager->memDb ){ pager_unwritelock(pPager); } pPager->errMask |= PAGER_ERR_MEM; return SQLITE_NOMEM; } memset(pPg, 0, sizeof(*pPg)); if( pPager->memDb ){ memset(PGHDR_TO_HIST(pPg, pPager), 0, sizeof(PgHistory)); } pPg->pPager = pPager; pPg->pNextAll = pPager->pAll; pPager->pAll = pPg; pPager->nPage++; }else{ /* Find a page to recycle. Try to locate a page that does not ** require us to do an fsync() on the journal. */ pPg = pPager->pFirstSynced; /* If we could not find a page that does not require an fsync() ** on the journal file then fsync the journal file. This is a ** very slow operation, so we work hard to avoid it. But sometimes ** it can't be helped. */ if( pPg==0 ){ int rc = syncJournal(pPager); if( rc!=0 ){ sqlite3pager_rollback(pPager); return SQLITE_IOERR; } if( pPager->fullSync ){ /* If in full-sync mode, write a new journal header into the ** journal file. This is done to avoid ever modifying a journal ** header that is involved in the rollback of pages that have ** already been written to the database (in case the header is ** trashed when the nRec field is updated). */ pPager->nRec = 0; assert( pPager->journalOff > 0 ); rc = writeJournalHdr(pPager); if( rc!=0 ){ sqlite3pager_rollback(pPager); return SQLITE_IOERR; } } pPg = pPager->pFirst; } assert( pPg->nRef==0 ); /* Write the page to the database file if it is dirty. */ if( pPg->dirty ){ assert( pPg->needSync==0 ); pPg->pDirty = 0; rc = pager_write_pagelist( pPg ); if( rc!=SQLITE_OK ){ sqlite3pager_rollback(pPager); return SQLITE_IOERR; } } assert( pPg->dirty==0 ); /* If the page we are recycling is marked as alwaysRollback, then ** set the global alwaysRollback flag, thus disabling the ** sqlite_dont_rollback() optimization for the rest of this transaction. ** It is necessary to do this because the page marked alwaysRollback ** might be reloaded at a later time but at that point we won't remember ** that is was marked alwaysRollback. This means that all pages must ** be marked as alwaysRollback from here on out. */ if( pPg->alwaysRollback ){ pPager->alwaysRollback = 1; } /* Unlink the old page from the free list and the hash table */ unlinkPage(pPg); pPager->nOvfl++; } pPg->pgno = pgno; if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){ sqlite3CheckMemory(pPager->aInJournal, pgno/8); assert( pPager->journalOpen ); pPg->inJournal = (pPager->aInJournal[pgno/8] & (1<<(pgno&7)))!=0; pPg->needSync = 0; }else{ pPg->inJournal = 0; pPg->needSync = 0; } if( pPager->aInStmt && (int)pgno<=pPager->stmtSize && (pPager->aInStmt[pgno/8] & (1<<(pgno&7)))!=0 ){ page_add_to_stmt_list(pPg); }else{ page_remove_from_stmt_list(pPg); } pPg->dirty = 0; pPg->nRef = 1; REFINFO(pPg); pPager->nRef++; h = pager_hash(pgno); pPg->pNextHash = pPager->aHash[h]; pPager->aHash[h] = pPg; if( pPg->pNextHash ){ assert( pPg->pNextHash->pPrevHash==0 ); pPg->pNextHash->pPrevHash = pPg; } if( pPager->nExtra>0 ){ memset(PGHDR_TO_EXTRA(pPg, pPager), 0, pPager->nExtra); } sqlite3pager_pagecount(pPager); if( pPager->errMask!=0 ){ sqlite3pager_unref(PGHDR_TO_DATA(pPg)); rc = pager_errcode(pPager); return rc; } if( pPager->dbSize<(int)pgno ){ memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize); }else{ int rc; assert( pPager->memDb==0 ); sqlite3OsSeek(&pPager->fd, (pgno-1)*(off_t)pPager->pageSize); rc = sqlite3OsRead(&pPager->fd, PGHDR_TO_DATA(pPg), pPager->pageSize); TRACE3("FETCH %d page %d\n", pPager->fd.h, pPg->pgno); CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3); if( rc!=SQLITE_OK ){ off_t fileSize; if( sqlite3OsFileSize(&pPager->fd,&fileSize)!=SQLITE_OK || fileSize>=pgno*pPager->pageSize ){ sqlite3pager_unref(PGHDR_TO_DATA(pPg)); return rc; }else{ memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize); } } } }else{ /* The requested page is in the page cache. */ pPager->nHit++; page_ref(pPg); } *ppPage = PGHDR_TO_DATA(pPg); return SQLITE_OK; } /* ** Acquire a page if it is already in the in-memory cache. Do ** not read the page from disk. Return a pointer to the page, ** or 0 if the page is not in cache. ** ** See also sqlite3pager_get(). The difference between this routine ** and sqlite3pager_get() 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. */ void *sqlite3pager_lookup(Pager *pPager, Pgno pgno){ PgHdr *pPg; assert( pPager!=0 ); assert( pgno!=0 ); if( pPager->errMask & ~(PAGER_ERR_FULL) ){ return 0; } pPg = pager_lookup(pPager, pgno); if( pPg==0 ) return 0; page_ref(pPg); return PGHDR_TO_DATA(pPg); } /* ** Release a page. ** ** If the number of references to the page drop to zero, then the ** page is added to the LRU list. When all references to all pages ** are released, a rollback occurs and the lock on the database is ** removed. */ int sqlite3pager_unref(void *pData){ PgHdr *pPg; /* Decrement the reference count for this page */ pPg = DATA_TO_PGHDR(pData); assert( pPg->nRef>0 ); pPg->nRef--; REFINFO(pPg); /* When the number of references to a page reach 0, call the ** destructor and add the page to the freelist. */ if( pPg->nRef==0 ){ Pager *pPager; pPager = pPg->pPager; pPg->pNextFree = 0; pPg->pPrevFree = pPager->pLast; pPager->pLast = pPg; if( pPg->pPrevFree ){ pPg->pPrevFree->pNextFree = pPg; }else{ pPager->pFirst = pPg; } if( pPg->needSync==0 && pPager->pFirstSynced==0 ){ pPager->pFirstSynced = pPg; } if( pPager->xDestructor ){ pPager->xDestructor(pData, pPager->pageSize); } /* When all pages reach the freelist, drop the read lock from ** the database file. */ pPager->nRef--; assert( pPager->nRef>=0 ); if( pPager->nRef==0 && !pPager->memDb ){ pager_reset(pPager); } } return SQLITE_OK; } /* ** Create a journal file for pPager. There should already be a RESERVED ** or EXCLUSIVE lock on the database file when this routine is called. ** ** Return SQLITE_OK if everything. Return an error code and release the ** write lock if anything goes wrong. */ static int pager_open_journal(Pager *pPager){ int rc; assert( !pPager->memDb ); assert( pPager->state>=PAGER_RESERVED ); assert( pPager->journalOpen==0 ); assert( pPager->useJournal ); sqlite3pager_pagecount(pPager); pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 ); if( pPager->aInJournal==0 ){ sqlite3OsUnlock(&pPager->fd, SHARED_LOCK); pPager->state = PAGER_SHARED; return SQLITE_NOMEM; } rc = sqlite3OsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile); pPager->journalOff = 0; pPager->setMaster = 0; pPager->journalHdr = 0; if( rc!=SQLITE_OK ){ sqliteFree(pPager->aInJournal); pPager->aInJournal = 0; sqlite3OsUnlock(&pPager->fd, SHARED_LOCK); pPager->state = PAGER_SHARED; return rc; } sqlite3OsOpenDirectory(pPager->zDirectory, &pPager->jfd); pPager->journalOpen = 1; pPager->journalStarted = 0; pPager->needSync = 0; pPager->alwaysRollback = 0; pPager->nRec = 0; if( pPager->errMask!=0 ){ rc = pager_errcode(pPager); return rc; } pPager->origDbSize = pPager->dbSize; rc = writeJournalHdr(pPager); if( pPager->stmtAutoopen && rc==SQLITE_OK ){ rc = sqlite3pager_stmt_begin(pPager); } if( rc!=SQLITE_OK ){ rc = pager_unwritelock(pPager); if( rc==SQLITE_OK ){ rc = SQLITE_FULL; } } return rc; } /* ** Acquire a write-lock on the database. The lock is removed when ** the any of the following happen: ** ** * sqlite3pager_commit() is called. ** * sqlite3pager_rollback() is called. ** * sqlite3pager_close() is called. ** * sqlite3pager_unref() is called to on every outstanding page. ** ** The first parameter to this routine is a pointer to any open page of the ** database file. Nothing changes about the page - it is used merely to ** acquire a pointer to the Pager structure and as proof that there is ** already a read-lock on the database. ** ** The second parameter indicates how much space in bytes to reserve for a ** master journal file-name at the start of the journal when it is created. ** ** A journal file is opened if this is not a temporary file. For temporary ** files, the opening of the journal file is deferred until there is an ** actual need to write to the journal. ** ** If the database is already reserved for writing, this routine is a no-op. */ int sqlite3pager_begin(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); Pager *pPager = pPg->pPager; int rc = SQLITE_OK; assert( pPg->nRef>0 ); assert( pPager->state!=PAGER_UNLOCK ); if( pPager->state==PAGER_SHARED ){ assert( pPager->aInJournal==0 ); if( pPager->memDb ){ pPager->state = PAGER_EXCLUSIVE; pPager->origDbSize = pPager->dbSize; }else{ #ifdef SQLITE_BUSY_RESERVED_LOCK int busy = 1; do { rc = sqlite3OsLock(&pPager->fd, RESERVED_LOCK); }while( rc==SQLITE_BUSY && pPager->pBusyHandler && pPager->pBusyHandler->xFunc && pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++) ); #else rc = sqlite3OsLock(&pPager->fd, RESERVED_LOCK); #endif if( rc!=SQLITE_OK ){ /* We do not call the busy handler when we fail to get a reserved lock. ** The only reason we might fail is because another process is holding ** the reserved lock. But the other process will not be able to ** release its reserved lock until this process releases its shared ** lock. So we might as well fail in this process, let it release ** its shared lock so that the other process can commit. */ return rc; } pPager->state = PAGER_RESERVED; pPager->dirtyCache = 0; TRACE2("TRANSACTION %d\n", pPager->fd.h); if( pPager->useJournal && !pPager->tempFile ){ rc = pager_open_journal(pPager); } } } return rc; } /* ** Mark a data page as writeable. The page is written into the journal ** if it is not there already. This routine must be called before making ** changes to a page. ** ** The first time this routine is called, the pager creates a new ** journal and acquires a RESERVED lock on the database. If the RESERVED ** lock could not be acquired, this routine returns SQLITE_BUSY. The ** calling routine must check for that return value and be careful not to ** change any page data until this routine returns SQLITE_OK. ** ** If the journal file could not be written because the disk is full, ** then this routine returns SQLITE_FULL and does an immediate rollback. ** All subsequent write attempts also return SQLITE_FULL until there ** is a call to sqlite3pager_commit() or sqlite3pager_rollback() to ** reset. */ int sqlite3pager_write(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); Pager *pPager = pPg->pPager; int rc = SQLITE_OK; /* Check for errors */ if( pPager->errMask ){ return pager_errcode(pPager); } if( pPager->readOnly ){ return SQLITE_PERM; } assert( !pPager->setMaster ); /* Mark the page as dirty. If the page has already been written ** to the journal then we can return right away. */ pPg->dirty = 1; if( pPg->inJournal && (pPg->inStmt || pPager->stmtInUse==0) ){ pPager->dirtyCache = 1; return SQLITE_OK; } /* 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 = sqlite3pager_begin(pData); if( rc!=SQLITE_OK ){ return rc; } assert( pPager->state>=PAGER_RESERVED ); if( !pPager->journalOpen && pPager->useJournal ){ rc = pager_open_journal(pPager); if( rc!=SQLITE_OK ) return rc; } assert( pPager->journalOpen || !pPager->useJournal ); pPager->dirtyCache = 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( !pPg->inJournal && (pPager->useJournal || pPager->memDb) ){ if( (int)pPg->pgno <= pPager->origDbSize ){ int szPg; u32 saved; if( pPager->memDb ){ PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager); TRACE3("JOURNAL %d page %d\n", pPager->fd.h, pPg->pgno); assert( pHist->pOrig==0 ); pHist->pOrig = sqliteMallocRaw( pPager->pageSize ); if( pHist->pOrig ){ memcpy(pHist->pOrig, PGHDR_TO_DATA(pPg), pPager->pageSize); } }else{ u32 cksum; CODEC(pPager, pData, pPg->pgno, 7); cksum = pager_cksum(pPager, pPg->pgno, pData); saved = *(u32*)PGHDR_TO_EXTRA(pPg, pPager); store32bits(cksum, pPg, pPager->pageSize); szPg = pPager->pageSize+8; store32bits(pPg->pgno, pPg, -4); rc = sqlite3OsWrite(&pPager->jfd, &((char*)pData)[-4], szPg); pPager->journalOff += szPg; TRACE4("JOURNAL %d page %d needSync=%d\n", pPager->fd.h, pPg->pgno, pPg->needSync); CODEC(pPager, pData, pPg->pgno, 0); *(u32*)PGHDR_TO_EXTRA(pPg, pPager) = saved; if( rc!=SQLITE_OK ){ sqlite3pager_rollback(pPager); pPager->errMask |= PAGER_ERR_FULL; return rc; } pPager->nRec++; assert( pPager->aInJournal!=0 ); pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7); pPg->needSync = !pPager->noSync; if( pPager->stmtInUse ){ pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7); page_add_to_stmt_list(pPg); } } }else{ pPg->needSync = !pPager->journalStarted && !pPager->noSync; TRACE4("APPEND %d page %d needSync=%d\n", pPager->fd.h, pPg->pgno, pPg->needSync); } if( pPg->needSync ){ pPager->needSync = 1; } pPg->inJournal = 1; } /* If the statement journal is open and the page is not in it, ** then write the current page to the statement journal. Note that ** the statement journal format differs from the standard journal format ** in that it omits the checksums and the header. */ if( pPager->stmtInUse && !pPg->inStmt && (int)pPg->pgno<=pPager->stmtSize ){ assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize ); if( pPager->memDb ){ PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager); assert( pHist->pStmt==0 ); pHist->pStmt = sqliteMallocRaw( pPager->pageSize ); if( pHist->pStmt ){ memcpy(pHist->pStmt, PGHDR_TO_DATA(pPg), pPager->pageSize); } TRACE3("STMT-JOURNAL %d page %d\n", pPager->fd.h, pPg->pgno); }else{ store32bits(pPg->pgno, pPg, -4); CODEC(pPager, pData, pPg->pgno, 7); rc = sqlite3OsWrite(&pPager->stfd, ((char*)pData)-4, pPager->pageSize+4); TRACE3("STMT-JOURNAL %d page %d\n", pPager->fd.h, pPg->pgno); CODEC(pPager, pData, pPg->pgno, 0); if( rc!=SQLITE_OK ){ sqlite3pager_rollback(pPager); pPager->errMask |= PAGER_ERR_FULL; return rc; } pPager->stmtNRec++; assert( pPager->aInStmt!=0 ); pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7); } page_add_to_stmt_list(pPg); } /* Update the database size and return. */ if( pPager->dbSize<(int)pPg->pgno ){ pPager->dbSize = pPg->pgno; if( !pPager->memDb && pPager->dbSize==PENDING_BYTE/pPager->pageSize ){ pPager->dbSize++; } } return rc; } /* ** Return TRUE if the page given in the argument was previously passed ** to sqlite3pager_write(). In other words, return TRUE if it is ok ** to change the content of the page. */ int sqlite3pager_iswriteable(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); return pPg->dirty; } /* ** Replace the content of a single page with the information in the third ** argument. */ int sqlite3pager_overwrite(Pager *pPager, Pgno pgno, void *pData){ void *pPage; int rc; rc = sqlite3pager_get(pPager, pgno, &pPage); if( rc==SQLITE_OK ){ rc = sqlite3pager_write(pPage); if( rc==SQLITE_OK ){ memcpy(pPage, pData, pPager->pageSize); } sqlite3pager_unref(pPage); } return rc; } /* ** A call to this routine tells the pager that it is not necessary to ** write the information on page "pgno" back to the disk, even though ** that page might be marked as dirty. ** ** The overlying software layer calls this routine when all of the data ** on the given page is unused. The pager marks the page as clean so ** that it does not get written to disk. ** ** Tests show that this optimization, together with the ** sqlite3pager_dont_rollback() below, more than double the speed ** of large INSERT operations and quadruple the speed of large DELETEs. ** ** When this routine is called, set the alwaysRollback flag to true. ** Subsequent calls to sqlite3pager_dont_rollback() for the same page ** will thereafter be ignored. This is necessary to avoid a problem ** where a page with data is added to the freelist during one part of ** a transaction then removed from the freelist during a later part ** of the same transaction and reused for some other purpose. When it ** is first added to the freelist, this routine is called. When reused, ** the dont_rollback() routine is called. But because the page contains ** critical data, we still need to be sure it gets rolled back in spite ** of the dont_rollback() call. */ void sqlite3pager_dont_write(Pager *pPager, Pgno pgno){ PgHdr *pPg; if( pPager->memDb ) return; pPg = pager_lookup(pPager, pgno); pPg->alwaysRollback = 1; if( pPg && pPg->dirty ){ if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSizedbSize ){ /* If this pages is the last page in the file and the file has grown ** during the current transaction, then do NOT mark the page as clean. ** When the database file grows, we must make sure that the last page ** gets written at least once so that the disk file will be the correct ** size. If you do not write this page and the size of the file ** on the disk ends up being too small, that can lead to database ** corruption during the next transaction. */ }else{ TRACE3("DONT_WRITE page %d of %d\n", pgno, pPager->fd.h); pPg->dirty = 0; } } } /* ** A call to this routine tells the pager that if a rollback occurs, ** it is not necessary to restore the data on the given page. This ** means that the pager does not have to record the given page in the ** rollback journal. */ void sqlite3pager_dont_rollback(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); Pager *pPager = pPg->pPager; if( pPager->state!=PAGER_EXCLUSIVE || pPager->journalOpen==0 ) return; if( pPg->alwaysRollback || pPager->alwaysRollback || pPager->memDb ) return; if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){ assert( pPager->aInJournal!=0 ); pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7); pPg->inJournal = 1; if( pPager->stmtInUse ){ pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7); page_add_to_stmt_list(pPg); } TRACE3("DONT_ROLLBACK page %d of %d\n", pPg->pgno, pPager->fd.h); } if( pPager->stmtInUse && !pPg->inStmt && (int)pPg->pgno<=pPager->stmtSize ){ assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize ); assert( pPager->aInStmt!=0 ); pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7); page_add_to_stmt_list(pPg); } } /* ** Clear a PgHistory block */ static void clearHistory(PgHistory *pHist){ sqliteFree(pHist->pOrig); sqliteFree(pHist->pStmt); pHist->pOrig = 0; pHist->pStmt = 0; } /* ** Commit all changes to the database and release the write lock. ** ** If the commit fails for any reason, a rollback attempt is made ** and an error code is returned. If the commit worked, SQLITE_OK ** is returned. */ int sqlite3pager_commit(Pager *pPager){ int rc; PgHdr *pPg; if( pPager->errMask==PAGER_ERR_FULL ){ rc = sqlite3pager_rollback(pPager); if( rc==SQLITE_OK ){ rc = SQLITE_FULL; } return rc; } if( pPager->errMask!=0 ){ rc = pager_errcode(pPager); return rc; } if( pPager->statefd.h); if( pPager->memDb ){ pPg = pager_get_all_dirty_pages(pPager); while( pPg ){ clearHistory(PGHDR_TO_HIST(pPg, pPager)); pPg->dirty = 0; pPg->inJournal = 0; pPg->inStmt = 0; pPg->pPrevStmt = pPg->pNextStmt = 0; pPg = pPg->pDirty; } #ifndef NDEBUG for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager); assert( !pPg->alwaysRollback ); assert( !pHist->pOrig ); assert( !pHist->pStmt ); } #endif pPager->pStmt = 0; pPager->state = PAGER_SHARED; return SQLITE_OK; } if( pPager->dirtyCache==0 ){ /* Exit early (without doing the time-consuming sqlite3OsSync() calls) ** if there have been no changes to the database file. */ assert( pPager->needSync==0 ); rc = pager_unwritelock(pPager); pPager->dbSize = -1; return rc; } assert( pPager->journalOpen ); rc = sqlite3pager_sync(pPager, 0); if( rc!=SQLITE_OK ){ goto commit_abort; } rc = pager_unwritelock(pPager); pPager->dbSize = -1; return rc; /* Jump here if anything goes wrong during the commit process. */ commit_abort: rc = sqlite3pager_rollback(pPager); if( rc==SQLITE_OK ){ rc = SQLITE_FULL; } return rc; } /* ** Rollback all changes. The database falls back to PAGER_SHARED mode. ** All in-memory cache pages revert to their original data contents. ** The journal is deleted. ** ** This routine cannot fail unless some other process is not following ** the correct locking protocol (SQLITE_PROTOCOL) or unless some other ** process is writing trash into the journal file (SQLITE_CORRUPT) or ** unless a prior malloc() failed (SQLITE_NOMEM). Appropriate error ** codes are returned for all these occasions. Otherwise, ** SQLITE_OK is returned. */ int sqlite3pager_rollback(Pager *pPager){ int rc; TRACE2("ROLLBACK %d\n", pPager->fd.h); if( pPager->memDb ){ PgHdr *p; for(p=pPager->pAll; p; p=p->pNextAll){ PgHistory *pHist; assert( !p->alwaysRollback ); if( !p->dirty ){ assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pOrig ); assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pStmt ); continue; } pHist = PGHDR_TO_HIST(p, pPager); if( pHist->pOrig ){ memcpy(PGHDR_TO_DATA(p), pHist->pOrig, pPager->pageSize); TRACE3("ROLLBACK-PAGE %d of %d\n", p->pgno, pPager->fd.h); }else{ TRACE3("PAGE %d is clean on %d\n", p->pgno, pPager->fd.h); } clearHistory(pHist); p->dirty = 0; p->inJournal = 0; p->inStmt = 0; p->pPrevStmt = p->pNextStmt = 0; if( pPager->xReiniter ){ pPager->xReiniter(PGHDR_TO_DATA(p), pPager->pageSize); } } pPager->pStmt = 0; pPager->dbSize = pPager->origDbSize; memoryTruncate(pPager); pPager->stmtInUse = 0; pPager->state = PAGER_SHARED; return SQLITE_OK; } if( !pPager->dirtyCache || !pPager->journalOpen ){ rc = pager_unwritelock(pPager); pPager->dbSize = -1; return rc; } if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){ if( pPager->state>=PAGER_EXCLUSIVE ){ pager_playback(pPager); } return pager_errcode(pPager); } if( pPager->state==PAGER_RESERVED ){ int rc2, rc3; rc = pager_reload_cache(pPager); rc2 = pager_truncate(pPager, pPager->origDbSize); rc3 = pager_unwritelock(pPager); if( rc==SQLITE_OK ){ rc = rc2; if( rc3 ) rc = rc3; } }else{ rc = pager_playback(pPager); } if( rc!=SQLITE_OK ){ rc = SQLITE_CORRUPT; pPager->errMask |= PAGER_ERR_CORRUPT; } pPager->dbSize = -1; return rc; } /* ** Return TRUE if the database file is opened read-only. Return FALSE ** if the database is (in theory) writable. */ int sqlite3pager_isreadonly(Pager *pPager){ return pPager->readOnly; } /* ** This routine is used for testing and analysis only. */ int *sqlite3pager_stats(Pager *pPager){ static int a[9]; a[0] = pPager->nRef; a[1] = pPager->nPage; a[2] = pPager->mxPage; a[3] = pPager->dbSize; a[4] = pPager->state; a[5] = pPager->errMask; a[6] = pPager->nHit; a[7] = pPager->nMiss; a[8] = pPager->nOvfl; return a; } /* ** Set the statement rollback point. ** ** This routine should be called with the transaction journal already ** open. A new statement journal is created that can be used to rollback ** changes of a single SQL command within a larger transaction. */ int sqlite3pager_stmt_begin(Pager *pPager){ int rc; char zTemp[SQLITE_TEMPNAME_SIZE]; assert( !pPager->stmtInUse ); assert( pPager->dbSize>=0 ); TRACE2("STMT-BEGIN %d\n", pPager->fd.h); if( pPager->memDb ){ pPager->stmtInUse = 1; pPager->stmtSize = pPager->dbSize; return SQLITE_OK; } if( !pPager->journalOpen ){ pPager->stmtAutoopen = 1; return SQLITE_OK; } assert( pPager->journalOpen ); pPager->aInStmt = sqliteMalloc( pPager->dbSize/8 + 1 ); if( pPager->aInStmt==0 ){ sqlite3OsLock(&pPager->fd, SHARED_LOCK); return SQLITE_NOMEM; } #ifndef NDEBUG rc = sqlite3OsFileSize(&pPager->jfd, &pPager->stmtJSize); if( rc ) goto stmt_begin_failed; assert( pPager->stmtJSize == pPager->journalOff ); #endif pPager->stmtJSize = pPager->journalOff; pPager->stmtSize = pPager->dbSize; pPager->stmtHdrOff = 0; pPager->stmtCksum = pPager->cksumInit; if( !pPager->stmtOpen ){ rc = sqlite3pager_opentemp(zTemp, &pPager->stfd); if( rc ) goto stmt_begin_failed; pPager->stmtOpen = 1; pPager->stmtNRec = 0; } pPager->stmtInUse = 1; return SQLITE_OK; stmt_begin_failed: if( pPager->aInStmt ){ sqliteFree(pPager->aInStmt); pPager->aInStmt = 0; } return rc; } /* ** Commit a statement. */ int sqlite3pager_stmt_commit(Pager *pPager){ if( pPager->stmtInUse ){ PgHdr *pPg, *pNext; TRACE2("STMT-COMMIT %d\n", pPager->fd.h); if( !pPager->memDb ){ sqlite3OsSeek(&pPager->stfd, 0); /* sqlite3OsTruncate(&pPager->stfd, 0); */ sqliteFree( pPager->aInStmt ); pPager->aInStmt = 0; } for(pPg=pPager->pStmt; pPg; pPg=pNext){ pNext = pPg->pNextStmt; assert( pPg->inStmt ); pPg->inStmt = 0; pPg->pPrevStmt = pPg->pNextStmt = 0; if( pPager->memDb ){ PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager); sqliteFree(pHist->pStmt); pHist->pStmt = 0; } } pPager->stmtNRec = 0; pPager->stmtInUse = 0; pPager->pStmt = 0; } pPager->stmtAutoopen = 0; return SQLITE_OK; } /* ** Rollback a statement. */ int sqlite3pager_stmt_rollback(Pager *pPager){ int rc; if( pPager->stmtInUse ){ TRACE2("STMT-ROLLBACK %d\n", pPager->fd.h); if( pPager->memDb ){ PgHdr *pPg; for(pPg=pPager->pStmt; pPg; pPg=pPg->pNextStmt){ PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager); if( pHist->pStmt ){ memcpy(PGHDR_TO_DATA(pPg), pHist->pStmt, pPager->pageSize); sqliteFree(pHist->pStmt); pHist->pStmt = 0; } } pPager->dbSize = pPager->stmtSize; memoryTruncate(pPager); rc = SQLITE_OK; }else{ rc = pager_stmt_playback(pPager); } sqlite3pager_stmt_commit(pPager); }else{ rc = SQLITE_OK; } pPager->stmtAutoopen = 0; return rc; } /* ** Return the full pathname of the database file. */ const char *sqlite3pager_filename(Pager *pPager){ return pPager->zFilename; } /* ** Return the directory of the database file. */ const char *sqlite3pager_dirname(Pager *pPager){ return pPager->zDirectory; } /* ** Return the full pathname of the journal file. */ const char *sqlite3pager_journalname(Pager *pPager){ return pPager->zJournal; } /* ** Set the codec for this pager */ void sqlite3pager_set_codec( Pager *pPager, void (*xCodec)(void*,void*,Pgno,int), void *pCodecArg ){ pPager->xCodec = xCodec; pPager->pCodecArg = pCodecArg; } /* ** This routine is called to increment the database file change-counter, ** stored at byte 24 of the pager file. */ static int pager_incr_changecounter(Pager *pPager){ void *pPage; PgHdr *pPgHdr; u32 change_counter; int rc; /* Open page 1 of the file for writing. */ rc = sqlite3pager_get(pPager, 1, &pPage); if( rc!=SQLITE_OK ) return rc; rc = sqlite3pager_write(pPage); if( rc!=SQLITE_OK ) return rc; /* Read the current value at byte 24. */ pPgHdr = DATA_TO_PGHDR(pPage); change_counter = retrieve32bits(pPgHdr, 24); /* Increment the value just read and write it back to byte 24. */ change_counter++; store32bits(change_counter, pPgHdr, 24); /* Release the page reference. */ sqlite3pager_unref(pPage); return SQLITE_OK; } /* ** Sync the database file for the pager pPager. zMaster points to the name ** of a master journal file that should be written into the individual ** journal file. zMaster may be NULL, which is interpreted as no master ** journal (a single database transaction). ** ** This routine ensures that the journal is synced, all dirty pages written ** to the database file and the database file synced. The only thing that ** remains to commit the transaction is to delete the journal file (or ** master journal file if specified). ** ** Note that if zMaster==NULL, this does not overwrite a previous value ** passed to an sqlite3pager_sync() call. */ int sqlite3pager_sync(Pager *pPager, const char *zMaster){ int rc = SQLITE_OK; /* If this is an in-memory db, or no pages have been written to, or this ** function has already been called, it is a no-op. */ if( pPager->state!=PAGER_SYNCED && !pPager->memDb && pPager->dirtyCache ){ PgHdr *pPg; assert( pPager->journalOpen ); /* If a master journal file name has already been written to the ** journal file, then no sync is required. This happens when it is ** written, then the process fails to upgrade from a RESERVED to an ** EXCLUSIVE lock. The next time the process tries to commit the ** transaction the m-j name will have already been written. */ if( !pPager->setMaster ){ rc = pager_incr_changecounter(pPager); if( rc!=SQLITE_OK ) goto sync_exit; rc = writeMasterJournal(pPager, zMaster); if( rc!=SQLITE_OK ) goto sync_exit; rc = syncJournal(pPager); if( rc!=SQLITE_OK ) goto sync_exit; } /* Write all dirty pages to the database file */ pPg = pager_get_all_dirty_pages(pPager); rc = pager_write_pagelist(pPg); if( rc!=SQLITE_OK ) goto sync_exit; /* Sync the database file. */ if( !pPager->noSync ){ rc = sqlite3OsSync(&pPager->fd); } pPager->state = PAGER_SYNCED; } sync_exit: return rc; } #if defined(SQLITE_DEBUG) || defined(SQLITE_TEST) /* ** Return the current state of the file lock for the given pager. ** The return value is one of NO_LOCK, SHARED_LOCK, RESERVED_LOCK, ** PENDING_LOCK, or EXCLUSIVE_LOCK. */ int sqlite3pager_lockstate(Pager *pPager){ #ifdef OS_TEST return pPager->fd->fd.locktype; #else return pPager->fd.locktype; #endif } #endif #ifdef SQLITE_TEST /* ** Print a listing of all referenced pages and their ref count. */ void sqlite3pager_refdump(Pager *pPager){ PgHdr *pPg; for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ if( pPg->nRef<=0 ) continue; printf("PAGE %3d addr=0x%08x nRef=%d\n", pPg->pgno, (int)PGHDR_TO_DATA(pPg), pPg->nRef); } } #endif