diff options
Diffstat (limited to 'ext/sqlite/libsqlite/src/pager.c')
| -rw-r--r-- | ext/sqlite/libsqlite/src/pager.c | 2022 |
1 files changed, 2022 insertions, 0 deletions
diff --git a/ext/sqlite/libsqlite/src/pager.c b/ext/sqlite/libsqlite/src/pager.c new file mode 100644 index 0000000000..7b32f6e089 --- /dev/null +++ b/ext/sqlite/libsqlite/src/pager.c @@ -0,0 +1,2022 @@ +/* +** 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. +** +** @(#) $Id$ +*/ +#include "os.h" /* Must be first to enable large file support */ +#include "sqliteInt.h" +#include "pager.h" +#include <assert.h> +#include <string.h> + +/* +** Macros for troubleshooting. Normally turned off +*/ +#if 0 +static Pager *mainPager = 0; +#define SET_PAGER(X) if( mainPager==0 ) mainPager = (X) +#define CLR_PAGER(X) if( mainPager==(X) ) mainPager = 0 +#define TRACE1(X) if( pPager==mainPager ) fprintf(stderr,X) +#define TRACE2(X,Y) if( pPager==mainPager ) fprintf(stderr,X,Y) +#define TRACE3(X,Y,Z) if( pPager==mainPager ) fprintf(stderr,X,Y,Z) +#else +#define SET_PAGER(X) +#define CLR_PAGER(X) +#define TRACE1(X) +#define TRACE2(X,Y) +#define TRACE3(X,Y,Z) +#endif + + +/* +** The page cache as a whole is always in one of the following +** states: +** +** SQLITE_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. +** +** SQLITE_READLOCK 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. +** +** SQLITE_WRITELOCK 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. +** +** The page cache comes up in SQLITE_UNLOCK. The first time a +** sqlite_page_get() occurs, the state transitions to SQLITE_READLOCK. +** After all pages have been released using sqlite_page_unref(), +** the state transitions back to SQLITE_UNLOCK. The first time +** that sqlite_page_write() is called, the state transitions to +** SQLITE_WRITELOCK. (Note that sqlite_page_write() can only be +** called on an outstanding page which means that the pager must +** be in SQLITE_READLOCK before it transitions to SQLITE_WRITELOCK.) +** The sqlite_page_rollback() and sqlite_page_commit() functions +** transition the state from SQLITE_WRITELOCK back to SQLITE_READLOCK. +*/ +#define SQLITE_UNLOCK 0 +#define SQLITE_READLOCK 1 +#define SQLITE_WRITELOCK 2 + + +/* +** 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. +*/ +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 */ + int nRef; /* Number of users of this page */ + PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */ + PgHdr *pNextAll, *pPrevAll; /* A list of all pages */ + PgHdr *pNextCkpt, *pPrevCkpt; /* List of pages in the checkpoint journal */ + u8 inJournal; /* TRUE if has been written to journal */ + u8 inCkpt; /* TRUE if written to the checkpoint journal */ + 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 */ + PgHdr *pDirty; /* Dirty pages sorted by PgHdr.pgno */ + /* SQLITE_PAGE_SIZE bytes of page data follow this header */ + /* Pager.nExtra bytes of local data follow the page data */ +}; + +/* +** 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(P) ((void*)&((char*)(&(P)[1]))[SQLITE_PAGE_SIZE]) + +/* +** 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 */ + OsFile fd, jfd; /* File descriptors for database and journal */ + OsFile cpfd; /* File descriptor for the checkpoint journal */ + int dbSize; /* Number of pages in the file */ + int origDbSize; /* dbSize before the current change */ + int ckptSize; /* Size of database (in pages) at ckpt_begin() */ + off_t ckptJSize; /* Size of journal at ckpt_begin() */ + int nRec; /* Number of pages written to the journal */ + u32 cksumInit; /* Quasi-random value added to every checksum */ + int ckptNRec; /* Number of records in the checkpoint journal */ + int nExtra; /* Add this many bytes to each in-memory page */ + void (*xDestructor)(void*); /* Call this routine when freeing pages */ + 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 */ + u8 journalOpen; /* True if journal file descriptors is valid */ + u8 journalStarted; /* True if initial magic of journal is synced */ + u8 useJournal; /* Do not use a rollback journal on this file */ + u8 ckptOpen; /* True if the checkpoint journal is open */ + u8 ckptInUse; /* True we are in a checkpoint */ + u8 ckptAutoopen; /* Open ckpt 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; /* SQLITE_UNLOCK, _READLOCK or _WRITELOCK */ + 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 dirtyFile; /* True if database file has changed in any way */ + u8 alwaysRollback; /* Disable dont_rollback() for all pages */ + u8 *aInJournal; /* One bit for each page in the database file */ + u8 *aInCkpt; /* One bit for each page in the database */ + PgHdr *pFirst, *pLast; /* List of free pages */ + PgHdr *pFirstSynced; /* First free page with PgHdr.needSync==0 */ + PgHdr *pAll; /* List of all pages */ + PgHdr *pCkpt; /* List of pages in the checkpoint journal */ + PgHdr *aHash[N_PG_HASH]; /* Hash table to map page number of PgHdr */ +}; + +/* +** 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? */ + +/* +** The journal file contains page records in the following +** format. +** +** Actually, this structure is the complete page record for pager +** formats less than 3. Beginning with format 3, this record is surrounded +** by two checksums. +*/ +typedef struct PageRecord PageRecord; +struct PageRecord { + Pgno pgno; /* The page number */ + char aData[SQLITE_PAGE_SIZE]; /* Original data for page pgno */ +}; + +/* +** Journal files begin with the following magic string. The data +** was obtained from /dev/random. It is used only as a sanity check. +** +** There are three journal formats (so far). The 1st journal format writes +** 32-bit integers in the byte-order of the host machine. New +** formats writes integers as big-endian. All new journals use the +** new format, but we have to be able to read an older journal in order +** to rollback journals created by older versions of the library. +** +** The 3rd journal format (added for 2.8.0) adds additional sanity +** checking information to the journal. 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 3rd journal format consists +** of a 32-bit checksum on each page of data. The checksum covers both +** the page number and the SQLITE_PAGE_SIZE 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 aJournalMagic1[] = { + 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd4, +}; +static const unsigned char aJournalMagic2[] = { + 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd5, +}; +static const unsigned char aJournalMagic3[] = { + 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd6, +}; +#define JOURNAL_FORMAT_1 1 +#define JOURNAL_FORMAT_2 2 +#define JOURNAL_FORMAT_3 3 + +/* +** The following integer determines what format to use when creating +** new primary journal files. By default we always use format 3. +** When testing, we can set this value to older journal formats in order to +** make sure that newer versions of the library are able to rollback older +** journal files. +** +** Note that checkpoint journals always use format 2 and omit the header. +*/ +#ifdef SQLITE_TEST +int journal_format = 3; +#else +# define journal_format 3 +#endif + +/* +** The size of the header and of each page in the journal varies according +** to which journal format is being used. The following macros figure out +** the sizes based on format numbers. +*/ +#define JOURNAL_HDR_SZ(X) \ + (sizeof(aJournalMagic1) + sizeof(Pgno) + ((X)>=3)*2*sizeof(u32)) +#define JOURNAL_PG_SZ(X) \ + (SQLITE_PAGE_SIZE + sizeof(Pgno) + ((X)>=3)*sizeof(u32)) + +/* +** Enable reference count tracking here: +*/ +#ifdef SQLITE_TEST + int pager_refinfo_enable = 0; + static void pager_refinfo(PgHdr *p){ + static int cnt = 0; + if( !pager_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 +*/ +static int read32bits(int format, OsFile *fd, u32 *pRes){ + u32 res; + int rc; + rc = sqliteOsRead(fd, &res, sizeof(res)); + if( rc==SQLITE_OK && format>JOURNAL_FORMAT_1 ){ + 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. Writing +** is always done using the new journal format. +*/ +static int write32bits(OsFile *fd, u32 val){ + unsigned char ac[4]; + if( journal_format<=1 ){ + return sqliteOsWrite(fd, &val, 4); + } + ac[0] = (val>>24) & 0xff; + ac[1] = (val>>16) & 0xff; + ac[2] = (val>>8) & 0xff; + ac[3] = val & 0xff; + return sqliteOsWrite(fd, ac, 4); +} + +/* +** Write a 32-bit integer into a page header right before the +** page data. This will overwrite the PgHdr.pDirty pointer. +*/ +static void store32bits(u32 val, PgHdr *p, int offset){ + unsigned char *ac; + ac = &((char*)PGHDR_TO_DATA(p))[offset]; + if( journal_format<=1 ){ + memcpy(ac, &val, 4); + }else{ + ac[0] = (val>>24) & 0xff; + ac[1] = (val>>16) & 0xff; + ac[2] = (val>>8) & 0xff; + ac[3] = val & 0xff; + } +} + + +/* +** 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; +} + +/* +** Add or remove a page from the list of all pages that are in the +** checkpoint journal. +** +** The Pager keeps a separate list of pages that are currently in +** the checkpoint journal. This helps the sqlitepager_ckpt_commit() +** routine run MUCH faster for the common case where there are many +** pages in memory but only a few are in the checkpoint journal. +*/ +static void page_add_to_ckpt_list(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + if( pPg->inCkpt ) return; + assert( pPg->pPrevCkpt==0 && pPg->pNextCkpt==0 ); + pPg->pPrevCkpt = 0; + if( pPager->pCkpt ){ + pPager->pCkpt->pPrevCkpt = pPg; + } + pPg->pNextCkpt = pPager->pCkpt; + pPager->pCkpt = pPg; + pPg->inCkpt = 1; +} +static void page_remove_from_ckpt_list(PgHdr *pPg){ + if( !pPg->inCkpt ) return; + if( pPg->pPrevCkpt ){ + assert( pPg->pPrevCkpt->pNextCkpt==pPg ); + pPg->pPrevCkpt->pNextCkpt = pPg->pNextCkpt; + }else{ + assert( pPg->pPager->pCkpt==pPg ); + pPg->pPager->pCkpt = pPg->pNextCkpt; + } + if( pPg->pNextCkpt ){ + assert( pPg->pNextCkpt->pPrevCkpt==pPg ); + pPg->pNextCkpt->pPrevCkpt = pPg->pPrevCkpt; + } + pPg->pNextCkpt = 0; + pPg->pPrevCkpt = 0; + pPg->inCkpt = 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>=SQLITE_WRITELOCK ){ + sqlitepager_rollback(pPager); + } + sqliteOsUnlock(&pPager->fd); + pPager->state = SQLITE_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 write lock on the database. This routine releases the database +** write lock and acquires a read lock in its place. The journal file +** is deleted and closed. +*/ +static int pager_unwritelock(Pager *pPager){ + int rc; + PgHdr *pPg; + if( pPager->state<SQLITE_WRITELOCK ) return SQLITE_OK; + sqlitepager_ckpt_commit(pPager); + if( pPager->ckptOpen ){ + sqliteOsClose(&pPager->cpfd); + pPager->ckptOpen = 0; + } + if( pPager->journalOpen ){ + sqliteOsClose(&pPager->jfd); + pPager->journalOpen = 0; + sqliteOsDelete(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; + } + }else{ + assert( pPager->dirtyFile==0 || pPager->useJournal==0 ); + } + rc = sqliteOsReadLock(&pPager->fd); + if( rc==SQLITE_OK ){ + pPager->state = SQLITE_READLOCK; + }else{ + /* This can only happen if a process does a BEGIN, then forks and the + ** child process does the COMMIT. Because of the semantics of unix + ** file locking, the unlock will fail. + */ + pPager->state = SQLITE_UNLOCK; + } + return rc; +} + +/* +** Compute and return a checksum for the page of data. +*/ +static u32 pager_cksum(Pager *pPager, Pgno pgno, const char *aData){ + u32 cksum = pPager->cksumInit + pgno; + return cksum; +} + +/* +** Read a single page from the journal file opened on file descriptor +** jfd. Playback this one page. +** +** There are three different journal formats. The format parameter determines +** which format is used by the journal that is played back. +*/ +static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int format){ + int rc; + PgHdr *pPg; /* An existing page in the cache */ + PageRecord pgRec; + u32 cksum; + + rc = read32bits(format, jfd, &pgRec.pgno); + if( rc!=SQLITE_OK ) return rc; + rc = sqliteOsRead(jfd, &pgRec.aData, sizeof(pgRec.aData)); + if( rc!=SQLITE_OK ) return rc; + + /* 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( pgRec.pgno==0 ){ + return SQLITE_DONE; + } + if( pgRec.pgno>pPager->dbSize ){ + return SQLITE_OK; + } + if( format>=JOURNAL_FORMAT_3 ){ + rc = read32bits(format, jfd, &cksum); + if( rc ) return rc; + if( pager_cksum(pPager, pgRec.pgno, pgRec.aData)!=cksum ){ + return SQLITE_DONE; + } + } + + /* Playback the page. Update the in-memory copy of the page + ** at the same time, if there is one. + */ + pPg = pager_lookup(pPager, pgRec.pgno); + TRACE2("PLAYBACK %d\n", pgRec.pgno); + sqliteOsSeek(&pPager->fd, (pgRec.pgno-1)*(off_t)SQLITE_PAGE_SIZE); + rc = sqliteOsWrite(&pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE); + if( pPg ){ + if( pPg->nRef==0 || + memcmp(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE)==0 + ){ + /* Do not update the data on this page if the page is in use + ** and the page has never been modified. This avoids resetting + ** the "extra" data. That in turn avoids invalidating BTree cursors + ** in trees that have never been modified. The end result is that + ** you can have a SELECT going on in one table and ROLLBACK changes + ** to a different table and the SELECT is unaffected by the ROLLBACK. + */ + memcpy(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE); + memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra); + } + pPg->dirty = 0; + pPg->needSync = 0; + } + return rc; +} + +/* +** 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: There is an initial +** file-type string for sanity checking. Then there is a single +** Pgno number which is the number of pages in the database before +** changes were made. The database is truncated to this size. +** Next come zero or more page records where each page record +** consists of a Pgno and SQLITE_PAGE_SIZE bytes of data. See +** the PageRecord structure for details. +** +** If the file opened as the journal file is not a well-formed +** journal file (as determined by looking at the magic number +** at the beginning) then this routine returns SQLITE_PROTOCOL. +** If any other errors occur during playback, the database will +** likely be corrupted, so the PAGER_ERR_CORRUPT bit is set in +** pPager->errMask and SQLITE_CORRUPT is returned. If it all +** works, then this routine returns SQLITE_OK. +*/ +static int pager_playback(Pager *pPager, int useJournalSize){ + off_t szJ; /* Size of the journal file in bytes */ + int nRec; /* Number of Records in the journal */ + int i; /* Loop counter */ + Pgno mxPg = 0; /* Size of the original file in pages */ + int format; /* Format of the journal file. */ + unsigned char aMagic[sizeof(aJournalMagic1)]; + int rc; + + /* Figure out how many records are in the journal. Abort early if + ** the journal is empty. + */ + assert( pPager->journalOpen ); + sqliteOsSeek(&pPager->jfd, 0); + rc = sqliteOsFileSize(&pPager->jfd, &szJ); + if( rc!=SQLITE_OK ){ + goto end_playback; + } + if( szJ < sizeof(aMagic)+sizeof(Pgno) ){ + goto end_playback; + } + + /* Read the beginning of the journal and truncate the + ** database file back to its original size. + */ + rc = sqliteOsRead(&pPager->jfd, aMagic, sizeof(aMagic)); + if( rc!=SQLITE_OK ){ + rc = SQLITE_PROTOCOL; + goto end_playback; + } + if( memcmp(aMagic, aJournalMagic3, sizeof(aMagic))==0 ){ + format = JOURNAL_FORMAT_3; + }else if( memcmp(aMagic, aJournalMagic2, sizeof(aMagic))==0 ){ + format = JOURNAL_FORMAT_2; + }else if( memcmp(aMagic, aJournalMagic1, sizeof(aMagic))==0 ){ + format = JOURNAL_FORMAT_1; + }else{ + rc = SQLITE_PROTOCOL; + goto end_playback; + } + if( format>=JOURNAL_FORMAT_3 ){ + rc = read32bits(format, &pPager->jfd, &nRec); + if( rc ) goto end_playback; + rc = read32bits(format, &pPager->jfd, &pPager->cksumInit); + if( rc ) goto end_playback; + if( nRec==0xffffffff || useJournalSize ){ + nRec = (szJ - JOURNAL_HDR_SZ(3))/JOURNAL_PG_SZ(3); + } + }else{ + nRec = (szJ - JOURNAL_HDR_SZ(2))/JOURNAL_PG_SZ(2); + assert( nRec*JOURNAL_PG_SZ(2)+JOURNAL_HDR_SZ(2)==szJ ); + } + rc = read32bits(format, &pPager->jfd, &mxPg); + if( rc!=SQLITE_OK ){ + goto end_playback; + } + assert( pPager->origDbSize==0 || pPager->origDbSize==mxPg ); + rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)mxPg); + if( rc!=SQLITE_OK ){ + goto end_playback; + } + pPager->dbSize = mxPg; + + /* Copy original pages out of the journal and back into the database file. + */ + for(i=0; i<nRec; i++){ + rc = pager_playback_one_page(pPager, &pPager->jfd, format); + if( rc!=SQLITE_OK ){ + if( rc==SQLITE_DONE ){ + rc = SQLITE_OK; + } + break; + } + } + + /* 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 the back from the original database. + */ + if( rc==SQLITE_OK ){ + PgHdr *pPg; + for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ + char zBuf[SQLITE_PAGE_SIZE]; + if( !pPg->dirty ) continue; + if( (int)pPg->pgno <= pPager->origDbSize ){ + sqliteOsSeek(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)(pPg->pgno-1)); + rc = sqliteOsRead(&pPager->fd, zBuf, SQLITE_PAGE_SIZE); + if( rc ) break; + }else{ + memset(zBuf, 0, SQLITE_PAGE_SIZE); + } + if( pPg->nRef==0 || memcmp(zBuf, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE) ){ + memcpy(PGHDR_TO_DATA(pPg), zBuf, SQLITE_PAGE_SIZE); + memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra); + } + pPg->needSync = 0; + pPg->dirty = 0; + } + } + +end_playback: + if( rc!=SQLITE_OK ){ + pager_unwritelock(pPager); + pPager->errMask |= PAGER_ERR_CORRUPT; + rc = SQLITE_CORRUPT; + }else{ + rc = pager_unwritelock(pPager); + } + return rc; +} + +/* +** Playback the checkpoint 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 checkpoint is stored in pPager->ckptSize, not in the +** journal file itself. +** +** (2) In addition to playing back the checkpoint journal, also +** playback all pages of the transaction journal beginning +** at offset pPager->ckptJSize. +*/ +static int pager_ckpt_playback(Pager *pPager){ + off_t szJ; /* Size of the full journal */ + int nRec; /* Number of Records */ + int i; /* Loop counter */ + int rc; + + /* Truncate the database back to its original size. + */ + rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)pPager->ckptSize); + pPager->dbSize = pPager->ckptSize; + + /* Figure out how many records are in the checkpoint journal. + */ + assert( pPager->ckptInUse && pPager->journalOpen ); + sqliteOsSeek(&pPager->cpfd, 0); + nRec = pPager->ckptNRec; + + /* Copy original pages out of the checkpoint journal and back into the + ** database file. Note that the checkpoint journal always uses format + ** 2 instead of format 3 since it does not need to be concerned with + ** power failures corrupting the journal and can thus omit the checksums. + */ + for(i=nRec-1; i>=0; i--){ + rc = pager_playback_one_page(pPager, &pPager->cpfd, 2); + assert( rc!=SQLITE_DONE ); + if( rc!=SQLITE_OK ) goto end_ckpt_playback; + } + + /* Figure out how many pages need to be copied out of the transaction + ** journal. + */ + rc = sqliteOsSeek(&pPager->jfd, pPager->ckptJSize); + if( rc!=SQLITE_OK ){ + goto end_ckpt_playback; + } + rc = sqliteOsFileSize(&pPager->jfd, &szJ); + if( rc!=SQLITE_OK ){ + goto end_ckpt_playback; + } + nRec = (szJ - pPager->ckptJSize)/JOURNAL_PG_SZ(journal_format); + for(i=nRec-1; i>=0; i--){ + rc = pager_playback_one_page(pPager, &pPager->jfd, journal_format); + if( rc!=SQLITE_OK ){ + assert( rc!=SQLITE_DONE ); + goto end_ckpt_playback; + } + } + +end_ckpt_playback: + if( rc!=SQLITE_OK ){ + pPager->errMask |= PAGER_ERR_CORRUPT; + rc = SQLITE_CORRUPT; + } + 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 sqliteOsSync(). 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 sqlitepager_set_cachesize(Pager *pPager, int mxPage){ + if( mxPage>=0 ){ + pPager->noSync = pPager->tempFile; + }else{ + pPager->noSync = 1; + mxPage = -mxPage; + } + if( mxPage>10 ){ + pPager->mxPage = 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 sqliteOsSync() 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 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 sqlitepager_set_safety_level(Pager *pPager, int level){ + pPager->noSync = level==1 || pPager->tempFile; + pPager->fullSync = level==3 && !pPager->tempFile; +} + +/* +** 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 sqlitepager_opentemp(char *zFile, OsFile *fd){ + int cnt = 8; + int rc; + do{ + cnt--; + sqliteOsTempFileName(zFile); + rc = sqliteOsOpenExclusive(zFile, fd, 1); + }while( cnt>0 && rc!=SQLITE_OK ); + 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 sqlitepager_get() and is only held open until the +** last page is released using sqlitepager_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. +*/ +int sqlitepager_open( + Pager **ppPager, /* Return the Pager structure here */ + const char *zFilename, /* Name of the database file to open */ + int mxPage, /* Max number of in-memory cache pages */ + 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; + int nameLen; + OsFile fd; + int rc; + int tempFile; + int readOnly = 0; + char zTemp[SQLITE_TEMPNAME_SIZE]; + + *ppPager = 0; + if( sqlite_malloc_failed ){ + return SQLITE_NOMEM; + } + if( zFilename ){ + zFullPathname = sqliteOsFullPathname(zFilename); + rc = sqliteOsOpenReadWrite(zFullPathname, &fd, &readOnly); + tempFile = 0; + }else{ + rc = sqlitepager_opentemp(zTemp, &fd); + zFilename = zTemp; + zFullPathname = sqliteOsFullPathname(zFilename); + tempFile = 1; + } + if( sqlite_malloc_failed ){ + return SQLITE_NOMEM; + } + if( rc!=SQLITE_OK ){ + sqliteFree(zFullPathname); + return SQLITE_CANTOPEN; + } + nameLen = strlen(zFullPathname); + pPager = sqliteMalloc( sizeof(*pPager) + nameLen*2 + 30 ); + if( pPager==0 ){ + sqliteOsClose(&fd); + sqliteFree(zFullPathname); + return SQLITE_NOMEM; + } + SET_PAGER(pPager); + pPager->zFilename = (char*)&pPager[1]; + pPager->zJournal = &pPager->zFilename[nameLen+1]; + strcpy(pPager->zFilename, zFullPathname); + strcpy(pPager->zJournal, zFullPathname); + sqliteFree(zFullPathname); + strcpy(&pPager->zJournal[nameLen], "-journal"); + pPager->fd = fd; + pPager->journalOpen = 0; + pPager->useJournal = useJournal; + pPager->ckptOpen = 0; + pPager->ckptInUse = 0; + pPager->nRef = 0; + pPager->dbSize = -1; + pPager->ckptSize = 0; + pPager->ckptJSize = 0; + pPager->nPage = 0; + pPager->mxPage = mxPage>5 ? mxPage : 10; + pPager->state = SQLITE_UNLOCK; + pPager->errMask = 0; + pPager->tempFile = tempFile; + pPager->readOnly = readOnly; + pPager->needSync = 0; + pPager->noSync = pPager->tempFile || !useJournal; + pPager->pFirst = 0; + pPager->pFirstSynced = 0; + pPager->pLast = 0; + pPager->nExtra = nExtra; + memset(pPager->aHash, 0, sizeof(pPager->aHash)); + *ppPager = pPager; + return SQLITE_OK; +} + +/* +** 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 sqlitepager_close(). +** Destructors are only called by sqlitepager_unref(). +*/ +void sqlitepager_set_destructor(Pager *pPager, void (*xDesc)(void*)){ + pPager->xDestructor = xDesc; +} + +/* +** Return the total number of pages in the disk file associated with +** pPager. +*/ +int sqlitepager_pagecount(Pager *pPager){ + off_t n; + assert( pPager!=0 ); + if( pPager->dbSize>=0 ){ + return pPager->dbSize; + } + if( sqliteOsFileSize(&pPager->fd, &n)!=SQLITE_OK ){ + pPager->errMask |= PAGER_ERR_DISK; + return 0; + } + n /= SQLITE_PAGE_SIZE; + if( pPager->state!=SQLITE_UNLOCK ){ + pPager->dbSize = n; + } + return n; +} + +/* +** 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 sqlitepager_close(Pager *pPager){ + PgHdr *pPg, *pNext; + switch( pPager->state ){ + case SQLITE_WRITELOCK: { + sqlitepager_rollback(pPager); + sqliteOsUnlock(&pPager->fd); + assert( pPager->journalOpen==0 ); + break; + } + case SQLITE_READLOCK: { + sqliteOsUnlock(&pPager->fd); + break; + } + default: { + /* Do nothing */ + break; + } + } + for(pPg=pPager->pAll; pPg; pPg=pNext){ + pNext = pPg->pNextAll; + sqliteFree(pPg); + } + sqliteOsClose(&pPager->fd); + assert( pPager->journalOpen==0 ); + /* Temp files are automatically deleted by the OS + ** if( pPager->tempFile ){ + ** sqliteOsDelete(pPager->zFilename); + ** } + */ + CLR_PAGER(pPager); + sqliteFree(pPager); + return SQLITE_OK; +} + +/* +** Return the page number for the given page data. +*/ +Pgno sqlitepager_pagenumber(void *pData){ + PgHdr *p = DATA_TO_PGHDR(pData); + return p->pgno; +} + +/* +** Increment 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. +*/ +#define page_ref(P) ((P)->nRef==0?_page_ref(P):(void)(P)->nRef++) +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); +} + +/* +** Increment the reference count for a page. The input pointer is +** a reference to the page data. +*/ +int sqlitepager_ref(void *pData){ + PgHdr *pPg = DATA_TO_PGHDR(pData); + page_ref(pPg); + return SQLITE_OK; +} + +/* +** Sync the journal and then write all free dirty pages to the database +** file. +** +** Writing all free dirty pages to the database after the sync is a +** non-obvious optimization. fsync() is an expensive operation so we +** want to minimize the number ot times it is called. After an fsync() call, +** we are free to write dirty pages back to the database. It is best +** to go ahead and write as many dirty pages as possible to minimize +** the risk of having to do another fsync() later on. Writing dirty +** free pages in this way was observed to make database operations go +** up to 10 times faster. +** +** If we are writing to temporary database, there is no need to preserve +** the integrity of the journal file, so we can save time and skip the +** fsync(). +*/ +static int syncAllPages(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 ); +#ifndef NDEBUG + { + off_t hdrSz, pgSz, jSz; + hdrSz = JOURNAL_HDR_SZ(journal_format); + pgSz = JOURNAL_PG_SZ(journal_format); + rc = sqliteOsFileSize(&pPager->jfd, &jSz); + if( rc!=0 ) return rc; + assert( pPager->nRec*pgSz+hdrSz==jSz ); + } +#endif + if( journal_format>=3 ){ + off_t szJ; + if( pPager->fullSync ){ + TRACE1("SYNC\n"); + rc = sqliteOsSync(&pPager->jfd); + if( rc!=0 ) return rc; + } + sqliteOsSeek(&pPager->jfd, sizeof(aJournalMagic1)); + rc = write32bits(&pPager->jfd, pPager->nRec); + if( rc ) return rc; + szJ = JOURNAL_HDR_SZ(journal_format) + + pPager->nRec*JOURNAL_PG_SZ(journal_format); + sqliteOsSeek(&pPager->jfd, szJ); + } + TRACE1("SYNC\n"); + rc = sqliteOsSync(&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; + + if( pList==0 ) return SQLITE_OK; + pPager = pList->pPager; + while( pList ){ + assert( pList->dirty ); + sqliteOsSeek(&pPager->fd, (pList->pgno-1)*(off_t)SQLITE_PAGE_SIZE); + rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pList), SQLITE_PAGE_SIZE); + 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 sqlitepager_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 sqlitepager_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 ); + if( pPager->errMask & ~(PAGER_ERR_FULL) ){ + return pager_errcode(pPager); + } + + /* If this is the first page accessed, then get a read lock + ** on the database file. + */ + if( pPager->nRef==0 ){ + rc = sqliteOsReadLock(&pPager->fd); + if( rc!=SQLITE_OK ){ + *ppPage = 0; + return rc; + } + pPager->state = SQLITE_READLOCK; + + /* If a journal file exists, try to play it back. + */ + if( pPager->useJournal && sqliteOsFileExists(pPager->zJournal) ){ + int rc, dummy; + + /* Get a write lock on the database + */ + rc = sqliteOsWriteLock(&pPager->fd); + if( rc!=SQLITE_OK ){ + if( sqliteOsUnlock(&pPager->fd)!=SQLITE_OK ){ + /* This should never happen! */ + rc = SQLITE_INTERNAL; + } + *ppPage = 0; + return rc; + } + pPager->state = SQLITE_WRITELOCK; + + /* Open the journal for exclusive access. Return SQLITE_BUSY if + ** we cannot get exclusive access to the journal file. + ** + ** Even though we will only be reading from the journal, not writing, + ** we have to open the journal for writing in order to obtain an + ** exclusive access lock. + */ + rc = sqliteOsOpenReadWrite(pPager->zJournal, &pPager->jfd, &dummy); + if( rc!=SQLITE_OK ){ + rc = sqliteOsUnlock(&pPager->fd); + assert( rc==SQLITE_OK ); + *ppPage = 0; + return SQLITE_BUSY; + } + pPager->journalOpen = 1; + pPager->journalStarted = 0; + + /* Playback and delete the journal. Drop the database write + ** lock and reacquire the read lock. + */ + rc = pager_playback(pPager, 0); + if( rc!=SQLITE_OK ){ + return rc; + } + } + pPg = 0; + }else{ + /* Search for page in cache */ + pPg = pager_lookup(pPager, pgno); + } + if( pPg==0 ){ + /* The requested page is not in the page cache. */ + int h; + pPager->nMiss++; + if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 ){ + /* Create a new page */ + pPg = sqliteMallocRaw( sizeof(*pPg) + SQLITE_PAGE_SIZE + + sizeof(u32) + pPager->nExtra ); + if( pPg==0 ){ + *ppPage = 0; + pager_unwritelock(pPager); + pPager->errMask |= PAGER_ERR_MEM; + return SQLITE_NOMEM; + } + memset(pPg, 0, sizeof(*pPg)); + pPg->pPager = pPager; + pPg->pNextAll = pPager->pAll; + if( pPager->pAll ){ + pPager->pAll->pPrevAll = pPg; + } + pPg->pPrevAll = 0; + 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 = syncAllPages(pPager); + if( rc!=0 ){ + sqlitepager_rollback(pPager); + *ppPage = 0; + 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 ){ + sqlitepager_rollback(pPager); + *ppPage = 0; + 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 + */ + if( pPg==pPager->pFirstSynced ){ + PgHdr *p = pPg->pNextFree; + while( p && p->needSync ){ p = p->pNextFree; } + pPager->pFirstSynced = p; + } + 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; + if( pPg->pNextHash ){ + pPg->pNextHash->pPrevHash = pPg->pPrevHash; + } + if( pPg->pPrevHash ){ + pPg->pPrevHash->pNextHash = pPg->pNextHash; + }else{ + h = pager_hash(pPg->pgno); + assert( pPager->aHash[h]==pPg ); + pPager->aHash[h] = pPg->pNextHash; + } + pPg->pNextHash = pPg->pPrevHash = 0; + pPager->nOvfl++; + } + pPg->pgno = pgno; + if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){ + sqliteCheckMemory(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->aInCkpt && (int)pgno<=pPager->ckptSize + && (pPager->aInCkpt[pgno/8] & (1<<(pgno&7)))!=0 ){ + page_add_to_ckpt_list(pPg); + }else{ + page_remove_from_ckpt_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->dbSize<0 ) sqlitepager_pagecount(pPager); + if( pPager->dbSize<(int)pgno ){ + memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE); + }else{ + int rc; + sqliteOsSeek(&pPager->fd, (pgno-1)*(off_t)SQLITE_PAGE_SIZE); + rc = sqliteOsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE); + if( rc!=SQLITE_OK ){ + off_t fileSize; + if( sqliteOsFileSize(&pPager->fd,&fileSize)!=SQLITE_OK + || fileSize>=pgno*SQLITE_PAGE_SIZE ){ + return rc; + }else{ + memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE); + } + } + } + if( pPager->nExtra>0 ){ + memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra); + } + }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 sqlitepager_get(). The difference between this routine +** and sqlitepager_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 *sqlitepager_lookup(Pager *pPager, Pgno pgno){ + PgHdr *pPg; + + assert( pPager!=0 ); + assert( pgno!=0 ); + if( pPager->errMask & ~(PAGER_ERR_FULL) ){ + return 0; + } + /* if( pPager->nRef==0 ){ + ** 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 sqlitepager_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); + } + + /* When all pages reach the freelist, drop the read lock from + ** the database file. + */ + pPager->nRef--; + assert( pPager->nRef>=0 ); + if( pPager->nRef==0 ){ + pager_reset(pPager); + } + } + return SQLITE_OK; +} + +/* +** Create a journal file for pPager. There should already be a write +** 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->state==SQLITE_WRITELOCK ); + assert( pPager->journalOpen==0 ); + assert( pPager->useJournal ); + pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 ); + if( pPager->aInJournal==0 ){ + sqliteOsReadLock(&pPager->fd); + pPager->state = SQLITE_READLOCK; + return SQLITE_NOMEM; + } + rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile); + if( rc!=SQLITE_OK ){ + sqliteFree(pPager->aInJournal); + pPager->aInJournal = 0; + sqliteOsReadLock(&pPager->fd); + pPager->state = SQLITE_READLOCK; + return SQLITE_CANTOPEN; + } + pPager->journalOpen = 1; + pPager->journalStarted = 0; + pPager->needSync = 0; + pPager->alwaysRollback = 0; + pPager->nRec = 0; + sqlitepager_pagecount(pPager); + pPager->origDbSize = pPager->dbSize; + if( journal_format==JOURNAL_FORMAT_3 ){ + rc = sqliteOsWrite(&pPager->jfd, aJournalMagic3, sizeof(aJournalMagic3)); + if( rc==SQLITE_OK ){ + rc = write32bits(&pPager->jfd, pPager->noSync ? 0xffffffff : 0); + } + if( rc==SQLITE_OK ){ + pPager->cksumInit = (u32)sqliteRandomInteger(); + rc = write32bits(&pPager->jfd, pPager->cksumInit); + } + }else if( journal_format==JOURNAL_FORMAT_2 ){ + rc = sqliteOsWrite(&pPager->jfd, aJournalMagic2, sizeof(aJournalMagic2)); + }else{ + assert( journal_format==JOURNAL_FORMAT_1 ); + rc = sqliteOsWrite(&pPager->jfd, aJournalMagic1, sizeof(aJournalMagic1)); + } + if( rc==SQLITE_OK ){ + rc = write32bits(&pPager->jfd, pPager->dbSize); + } + if( pPager->ckptAutoopen && rc==SQLITE_OK ){ + rc = sqlitepager_ckpt_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: +** +** * sqlitepager_commit() is called. +** * sqlitepager_rollback() is called. +** * sqlitepager_close() is called. +** * sqlitepager_unref() is called to on every outstanding page. +** +** The 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. +** +** 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 write-locked, this routine is a no-op. +*/ +int sqlitepager_begin(void *pData){ + PgHdr *pPg = DATA_TO_PGHDR(pData); + Pager *pPager = pPg->pPager; + int rc = SQLITE_OK; + assert( pPg->nRef>0 ); + assert( pPager->state!=SQLITE_UNLOCK ); + if( pPager->state==SQLITE_READLOCK ){ + assert( pPager->aInJournal==0 ); + rc = sqliteOsWriteLock(&pPager->fd); + if( rc!=SQLITE_OK ){ + return rc; + } + pPager->state = SQLITE_WRITELOCK; + pPager->dirtyFile = 0; + TRACE1("TRANSACTION\n"); + 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 write lock on the database. If the write +** 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 sqlitepager_commit() or sqlitepager_rollback() to +** reset. +*/ +int sqlitepager_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; + } + + /* 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->inCkpt || pPager->ckptInUse==0) ){ + pPager->dirtyFile = 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!=SQLITE_UNLOCK ); + rc = sqlitepager_begin(pData); + if( rc!=SQLITE_OK ){ + return rc; + } + assert( pPager->state==SQLITE_WRITELOCK ); + if( !pPager->journalOpen && pPager->useJournal ){ + rc = pager_open_journal(pPager); + if( rc!=SQLITE_OK ) return rc; + } + assert( pPager->journalOpen || !pPager->useJournal ); + pPager->dirtyFile = 1; + + /* The transaction journal now exists and we have a write 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 ){ + if( (int)pPg->pgno <= pPager->origDbSize ){ + int szPg; + u32 saved; + if( journal_format>=JOURNAL_FORMAT_3 ){ + u32 cksum = pager_cksum(pPager, pPg->pgno, pData); + saved = *(u32*)PGHDR_TO_EXTRA(pPg); + store32bits(cksum, pPg, SQLITE_PAGE_SIZE); + szPg = SQLITE_PAGE_SIZE+8; + }else{ + szPg = SQLITE_PAGE_SIZE+4; + } + store32bits(pPg->pgno, pPg, -4); + rc = sqliteOsWrite(&pPager->jfd, &((char*)pData)[-4], szPg); + if( journal_format>=JOURNAL_FORMAT_3 ){ + *(u32*)PGHDR_TO_EXTRA(pPg) = saved; + } + if( rc!=SQLITE_OK ){ + sqlitepager_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; + pPg->inJournal = 1; + if( pPager->ckptInUse ){ + pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7); + page_add_to_ckpt_list(pPg); + } + TRACE3("JOURNAL %d %d\n", pPg->pgno, pPg->needSync); + }else{ + pPg->needSync = !pPager->journalStarted && !pPager->noSync; + TRACE3("APPEND %d %d\n", pPg->pgno, pPg->needSync); + } + if( pPg->needSync ){ + pPager->needSync = 1; + } + } + + /* If the checkpoint journal is open and the page is not in it, + ** then write the current page to the checkpoint journal. Note that + ** the checkpoint journal always uses the simplier format 2 that lacks + ** checksums. The header is also omitted from the checkpoint journal. + */ + if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){ + assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize ); + store32bits(pPg->pgno, pPg, -4); + rc = sqliteOsWrite(&pPager->cpfd, &((char*)pData)[-4], SQLITE_PAGE_SIZE+4); + if( rc!=SQLITE_OK ){ + sqlitepager_rollback(pPager); + pPager->errMask |= PAGER_ERR_FULL; + return rc; + } + pPager->ckptNRec++; + assert( pPager->aInCkpt!=0 ); + pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7); + page_add_to_ckpt_list(pPg); + } + + /* Update the database size and return. + */ + if( pPager->dbSize<(int)pPg->pgno ){ + pPager->dbSize = pPg->pgno; + } + return rc; +} + +/* +** Return TRUE if the page given in the argument was previously passed +** to sqlitepager_write(). In other words, return TRUE if it is ok +** to change the content of the page. +*/ +int sqlitepager_iswriteable(void *pData){ + PgHdr *pPg = DATA_TO_PGHDR(pData); + return pPg->dirty; +} + +/* +** 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 +** sqlitepager_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 sqlitepager_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 sqlitepager_dont_write(Pager *pPager, Pgno pgno){ + PgHdr *pPg; + + pPg = pager_lookup(pPager, pgno); + pPg->alwaysRollback = 1; + if( pPg && pPg->dirty ){ + if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){ + /* If this pages is the last page in the file and the file has grown + ** during the current transaction, then do NOT mark the page as clean. + ** When the database file grows, we must make sure that the last page + ** gets written at least once so that the disk file will be the correct + ** size. If you do not write this page and the size of the file + ** on the disk ends up being too small, that can lead to database + ** corruption during the next transaction. + */ + }else{ + TRACE2("DONT_WRITE %d\n", pgno); + 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 sqlitepager_dont_rollback(void *pData){ + PgHdr *pPg = DATA_TO_PGHDR(pData); + Pager *pPager = pPg->pPager; + + if( pPager->state!=SQLITE_WRITELOCK || pPager->journalOpen==0 ) return; + if( pPg->alwaysRollback || pPager->alwaysRollback ) 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->ckptInUse ){ + pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7); + page_add_to_ckpt_list(pPg); + } + TRACE2("DONT_ROLLBACK %d\n", pPg->pgno); + } + if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){ + assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize ); + assert( pPager->aInCkpt!=0 ); + pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7); + page_add_to_ckpt_list(pPg); + } +} + +/* +** 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 sqlitepager_commit(Pager *pPager){ + int rc; + PgHdr *pPg; + + if( pPager->errMask==PAGER_ERR_FULL ){ + rc = sqlitepager_rollback(pPager); + if( rc==SQLITE_OK ){ + rc = SQLITE_FULL; + } + return rc; + } + if( pPager->errMask!=0 ){ + rc = pager_errcode(pPager); + return rc; + } + if( pPager->state!=SQLITE_WRITELOCK ){ + return SQLITE_ERROR; + } + TRACE1("COMMIT\n"); + if( pPager->dirtyFile==0 ){ + /* Exit early (without doing the time-consuming sqliteOsSync() 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 ); + if( pPager->needSync && sqliteOsSync(&pPager->jfd)!=SQLITE_OK ){ + goto commit_abort; + } + pPg = pager_get_all_dirty_pages(pPager); + if( pPg ){ + rc = pager_write_pagelist(pPg); + if( rc || (!pPager->noSync && sqliteOsSync(&pPager->fd)!=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 = sqlitepager_rollback(pPager); + if( rc==SQLITE_OK ){ + rc = SQLITE_FULL; + } + return rc; +} + +/* +** Rollback all changes. The database falls back to read-only 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 sqlitepager_rollback(Pager *pPager){ + int rc; + TRACE1("ROLLBACK\n"); + if( !pPager->dirtyFile || !pPager->journalOpen ){ + rc = pager_unwritelock(pPager); + pPager->dbSize = -1; + return rc; + } + + if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){ + if( pPager->state>=SQLITE_WRITELOCK ){ + pager_playback(pPager, 1); + } + return pager_errcode(pPager); + } + if( pPager->state!=SQLITE_WRITELOCK ){ + return SQLITE_OK; + } + rc = pager_playback(pPager, 1); + 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 sqlitepager_isreadonly(Pager *pPager){ + return pPager->readOnly; +} + +/* +** This routine is used for testing and analysis only. +*/ +int *sqlitepager_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 checkpoint. +** +** This routine should be called with the transaction journal already +** open. A new checkpoint journal is created that can be used to rollback +** changes of a single SQL command within a larger transaction. +*/ +int sqlitepager_ckpt_begin(Pager *pPager){ + int rc; + char zTemp[SQLITE_TEMPNAME_SIZE]; + if( !pPager->journalOpen ){ + pPager->ckptAutoopen = 1; + return SQLITE_OK; + } + assert( pPager->journalOpen ); + assert( !pPager->ckptInUse ); + pPager->aInCkpt = sqliteMalloc( pPager->dbSize/8 + 1 ); + if( pPager->aInCkpt==0 ){ + sqliteOsReadLock(&pPager->fd); + return SQLITE_NOMEM; + } +#ifndef NDEBUG + rc = sqliteOsFileSize(&pPager->jfd, &pPager->ckptJSize); + if( rc ) goto ckpt_begin_failed; + assert( pPager->ckptJSize == + pPager->nRec*JOURNAL_PG_SZ(journal_format)+JOURNAL_HDR_SZ(journal_format) ); +#endif + pPager->ckptJSize = pPager->nRec*JOURNAL_PG_SZ(journal_format) + + JOURNAL_HDR_SZ(journal_format); + pPager->ckptSize = pPager->dbSize; + if( !pPager->ckptOpen ){ + rc = sqlitepager_opentemp(zTemp, &pPager->cpfd); + if( rc ) goto ckpt_begin_failed; + pPager->ckptOpen = 1; + pPager->ckptNRec = 0; + } + pPager->ckptInUse = 1; + return SQLITE_OK; + +ckpt_begin_failed: + if( pPager->aInCkpt ){ + sqliteFree(pPager->aInCkpt); + pPager->aInCkpt = 0; + } + return rc; +} + +/* +** Commit a checkpoint. +*/ +int sqlitepager_ckpt_commit(Pager *pPager){ + if( pPager->ckptInUse ){ + PgHdr *pPg, *pNext; + sqliteOsSeek(&pPager->cpfd, 0); + /* sqliteOsTruncate(&pPager->cpfd, 0); */ + pPager->ckptNRec = 0; + pPager->ckptInUse = 0; + sqliteFree( pPager->aInCkpt ); + pPager->aInCkpt = 0; + for(pPg=pPager->pCkpt; pPg; pPg=pNext){ + pNext = pPg->pNextCkpt; + assert( pPg->inCkpt ); + pPg->inCkpt = 0; + pPg->pPrevCkpt = pPg->pNextCkpt = 0; + } + pPager->pCkpt = 0; + } + pPager->ckptAutoopen = 0; + return SQLITE_OK; +} + +/* +** Rollback a checkpoint. +*/ +int sqlitepager_ckpt_rollback(Pager *pPager){ + int rc; + if( pPager->ckptInUse ){ + rc = pager_ckpt_playback(pPager); + sqlitepager_ckpt_commit(pPager); + }else{ + rc = SQLITE_OK; + } + pPager->ckptAutoopen = 0; + return rc; +} + +#ifdef SQLITE_TEST +/* +** Print a listing of all referenced pages and their ref count. +*/ +void sqlitepager_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 |