** file simultaneously, or one process from reading the database while
** another is writing.
**
-** @(#) $Id: pager.c,v 1.551 2009/01/14 23:03:41 drh Exp $
+** @(#) $Id: pager.c,v 1.552 2009/01/16 15:21:06 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
/*
** A open page cache is an instance of the following structure.
**
-** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or
-** or SQLITE_FULL. Once one of the first three errors occurs, it persists
-** and is returned as the result of every major pager API call. The
-** SQLITE_FULL return code is slightly different. It persists only until the
-** next successful rollback is performed on the pager cache. Also,
-** SQLITE_FULL does not affect the sqlite3PagerGet() and sqlite3PagerLookup()
-** APIs, they may still be used successfully.
-**
-** Managing the size of the database file in pages is a little complicated.
-** The variable Pager.dbSize contains the number of pages that the database
-** image currently contains. As the database image grows or shrinks this
-** variable is updated. The variable Pager.dbFileSize contains the number
-** of pages in the database file. This may be different from Pager.dbSize
-** if some pages have been appended to the database image but not yet written
-** out from the cache to the actual file on disk. Or if the image has been
-** truncated by an incremental-vacuum operation. The Pager.dbOrigSize variable
-** contains the number of pages in the database image when the current
-** transaction was opened. The contents of all three of these variables is
-** only guaranteed to be correct if the boolean Pager.dbSizeValid is true.
+** errCode
+**
+** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or
+** or SQLITE_FULL. Once one of the first three errors occurs, it persists
+** and is returned as the result of every major pager API call. The
+** SQLITE_FULL return code is slightly different. It persists only until the
+** next successful rollback is performed on the pager cache. Also,
+** SQLITE_FULL does not affect the sqlite3PagerGet() and sqlite3PagerLookup()
+** APIs, they may still be used successfully.
+**
+** dbSizeValid, dbSize, dbOrigSize, dbFileSize
+**
+** Managing the size of the database file in pages is a little complicated.
+** The variable Pager.dbSize contains the number of pages that the database
+** image currently contains. As the database image grows or shrinks this
+** variable is updated. The variable Pager.dbFileSize contains the number
+** of pages in the database file. This may be different from Pager.dbSize
+** if some pages have been appended to the database image but not yet written
+** out from the cache to the actual file on disk. Or if the image has been
+** truncated by an incremental-vacuum operation. The Pager.dbOrigSize variable
+** contains the number of pages in the database image when the current
+** transaction was opened. The contents of all three of these variables is
+** only guaranteed to be correct if the boolean Pager.dbSizeValid is true.
+**
+** TODO: Under what conditions is dbSizeValid set? Cleared?
+**
+** changeCountDone
+**
+** This boolean variable is used to make sure that the change-counter
+** (the 4-byte header field at byte offset 24 of the database file) is
+** not updated more often than necessary.
+**
+** It is set to true when the change-counter field is updated, which
+** can only happen if an exclusive lock is held on the database file.
+** It is cleared (set to false) whenever an exclusive lock is
+** relinquished on the database file. Each time a transaction is committed,
+** The changeCountDone flag is inspected. If it is true, the work of
+** updating the change-counter is omitted for the current transaction.
+**
+** This mechanism means that when running in exclusive mode, a connection
+** need only update the change-counter once, for the first transaction
+** committed.
+**
+** dbModified
+**
+** The dbModified flag is set whenever a database page is dirtied.
+** It is cleared at the end of each transaction.
+**
+** It is used when committing or otherwise ending a transaction. If
+** the dbModified flag is clear then less work has to be done.
+**
+** TODO: Check some of the logic surrounding this optimization.
+**
+** journalStarted
+**
+** This flag is set whenever the the main journal is synced.
+**
+** The point of this flag is that it must be set after the
+** first journal header in a journal file has been synced to disk.
+** After this has happened, new pages appended to the database
+** do not need the PGHDR_NEED_SYNC flag set, as they do not need
+** to wait for a journal sync before they can be written out to
+** the database file (see function pager_write()).
+**
+** setMaster
+**
+** This variable is used to ensure that the master journal file name
+** (if any) is only written into the journal file once.
+**
+** When committing a transaction, the master journal file name (if any)
+** may be written into the journal file while the pager is still in
+** PAGER_RESERVED state (see CommitPhaseOne() for the action). It
+** then attempts to upgrade to an exclusive lock. If this attempt
+** fails, then SQLITE_BUSY may be returned to the user and the user
+** may attempt to commit the transaction again later (calling
+** CommitPhaseOne() again). This flag is used to ensure that the
+** master journal name is only written to the journal file the first
+** time CommitPhaseOne() is called.
+**
+** doNotSync
+**
+** This variable is set and cleared by sqlite3PagerWrite().
+**
+** needSync
+**
+** TODO: It might be easier to set this variable in writeJournalHdr()
+** and writeMasterJournal() only. Change its meaning to "unsynced data
+** has been written to the journal".
*/
struct Pager {
sqlite3_vfs *pVfs; /* OS functions to use for IO */
- u8 journalOpen; /* True if journal file descriptors is valid */
- u8 journalStarted; /* True if header of journal is synced */
+ u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
+ u8 journalMode; /* On of the PAGER_JOURNALMODE_* values */
u8 useJournal; /* Use a rollback journal on this file */
u8 noReadlock; /* Do not bother to obtain readlocks */
u8 noSync; /* Do not sync the journal if true */
u8 fullSync; /* Do extra syncs of the journal for robustness */
u8 sync_flags; /* One of SYNC_NORMAL or SYNC_FULL */
- u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */
u8 tempFile; /* zFilename is a temporary file */
u8 readOnly; /* True for a read-only database */
- u8 needSync; /* True if an fsync() is needed on the journal */
- u8 dirtyCache; /* True if cached pages have changed */
u8 memDb; /* True to inhibit all file I/O */
- u8 setMaster; /* True if a m-j name has been written to jrnl */
- u8 doNotSync; /* Boolean. While true, do not spill the cache */
- u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
- u8 journalMode; /* On of the PAGER_JOURNALMODE_* values */
+
+ /* The following block contains those class members that are dynamically
+ ** modified during normal operations. The other variables in this structure
+ ** are either constant throughout the lifetime of the pager, or else
+ ** used to store configuration parameters that affect the way the pager
+ ** operates.
+ **
+ ** The 'state' variable is described in more detail along with the
+ ** descriptions of the values it may take - PAGER_UNLOCK etc. Many of the
+ ** other variables in this block are described in the comment directly
+ ** above this class definition.
+ */
+ u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */
u8 dbModified; /* True if there are any changes to the Db */
+ u8 needSync; /* True if an fsync() is needed on the journal */
+ u8 journalStarted; /* True if header of journal is synced */
u8 changeCountDone; /* Set after incrementing the change-counter */
+ u8 setMaster; /* True if a m-j name has been written to jrnl */
+ u8 doNotSync; /* Boolean. While true, do not spill the cache */
u8 dbSizeValid; /* Set when dbSize is correct */
Pgno dbSize; /* Number of pages in the database */
Pgno dbOrigSize; /* dbSize before the current transaction */
Pgno dbFileSize; /* Number of pages in the database file */
- u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */
int errCode; /* One of several kinds of errors */
- int nRec; /* Number of pages written to the journal */
+ int nRec; /* Pages journalled since last j-header written */
u32 cksumInit; /* Quasi-random value added to every checksum */
- int stmtNRec; /* Number of records in stmt subjournal */
+ u32 nSubRec; /* Number of records written to sub-journal */
+ Bitvec *pInJournal; /* One bit for each page in the database file */
+ sqlite3_file *fd; /* File descriptor for database */
+ sqlite3_file *jfd; /* File descriptor for main journal */
+ sqlite3_file *sjfd; /* File descriptor for sub-journal */
+ i64 journalOff; /* Current write offset in the journal file */
+ i64 journalHdr; /* Byte offset to previous journal header */
+ PagerSavepoint *aSavepoint; /* Array of active savepoints */
+ int nSavepoint; /* Number of elements in aSavepoint[] */
+ char dbFileVers[16]; /* Changes whenever database file changes */
+ u32 sectorSize; /* Assumed sector size during rollback */
+
int nExtra; /* Add this many bytes to each in-memory page */
+ u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */
int pageSize; /* Number of bytes in a page */
- int nPage; /* Total number of in-memory pages */
- int mxPage; /* Maximum number of pages to hold in cache */
Pgno mxPgno; /* Maximum allowed size of the database */
- Bitvec *pInJournal; /* One bit for each page in the database file */
- Bitvec *pAlwaysRollback; /* One bit for each page marked always-rollback */
char *zFilename; /* Name of the database file */
char *zJournal; /* Name of the journal file */
- char *zDirectory; /* Directory hold database and journal files */
- sqlite3_file *fd, *jfd; /* File descriptors for database and journal */
- sqlite3_file *sjfd; /* File descriptor for the sub-journal*/
int (*xBusyHandler)(void*); /* Function to call when busy */
void *pBusyHandlerArg; /* Context argument for xBusyHandler */
- i64 journalOff; /* Current byte offset in the journal file */
- i64 journalHdr; /* Byte offset to previous journal header */
- u32 sectorSize; /* Assumed sector size during rollback */
#ifdef SQLITE_TEST
int nHit, nMiss; /* Cache hits and missing */
int nRead, nWrite; /* Database pages read/written */
void *pCodecArg; /* First argument to xCodec() */
#endif
char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */
- char dbFileVers[16]; /* Changes whenever database file changes */
i64 journalSizeLimit; /* Size limit for persistent journal files */
PCache *pPCache; /* Pointer to page cache object */
- PagerSavepoint *aSavepoint; /* Array of active savepoints */
- int nSavepoint; /* Number of elements in aSavepoint[] */
};
/*
};
/*
-** The size of the header and of each page in the journal is determined
-** by the following macros.
+** The size of the of each page record in the journal is given by
+** the following macro.
*/
#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8)
/*
-** The journal header size for this pager. 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.
+** The journal header size for this pager. This is usually the same
+** size as a single disk sector. See also setSectorSize().
*/
#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
# define MEMDB pPager->memDb
#endif
-/*
-** Page number PAGER_MJ_PGNO is never used in an SQLite database (it is
-** reserved for working around a windows/posix incompatibility). It is
-** used in the journal to signify that the remainder of the journal file
-** is devoted to storing a master journal name - there are no more pages to
-** roll back. See comments for function writeMasterJournal() for details.
-*/
-/* #define PAGER_MJ_PGNO(x) (PENDING_BYTE/((x)->pageSize)) */
-#define PAGER_MJ_PGNO(x) ((Pgno)((PENDING_BYTE/((x)->pageSize))+1))
-
/*
** The maximum legal page number is (2^31 - 1).
*/
return sqlite3OsWrite(fd, ac, 4, offset);
}
+/*
+** The argument to this macro is a file descriptor (type sqlite3_file*).
+** Return 0 if it is not open, or non-zero (but not 1) if it is.
+**
+** This is so that expressions can be written as:
+**
+** if( isOpen(pPager->jfd) ){ ...
+**
+** instead of
+**
+** if( pPager->jfd->pMethods ){ ...
+*/
+#define isOpen(pFd) ((pFd)->pMethods)
+
/*
** If file pFd is open, call sqlite3OsUnlock() on it.
*/
static int osUnlock(sqlite3_file *pFd, int eLock){
- if( !pFd->pMethods ){
+ if( !isOpen(pFd) ){
return SQLITE_OK;
}
return sqlite3OsUnlock(pFd, eLock);
** (b) the value returned by OsSectorSize() is less than or equal
** to the page size.
**
+** The optimization is also always enabled for temporary files. It is
+** an error to call this function if pPager is opened on an in-memory
+** database.
+**
** If the optimization cannot be used, 0 is returned. If it can be used,
** then the value returned is the size of the journal file when it
** contains rollback data for exactly one page.
*/
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
static int jrnlBufferSize(Pager *pPager){
- int dc; /* Device characteristics */
- int nSector; /* Sector size */
- int szPage; /* Page size */
- sqlite3_file *fd = pPager->fd;
+ assert( !MEMDB );
+ if( !pPager->tempFile ){
+ int dc; /* Device characteristics */
+ int nSector; /* Sector size */
+ int szPage; /* Page size */
- if( fd->pMethods ){
- dc = sqlite3OsDeviceCharacteristics(fd);
+ assert( isOpen(pPager->fd) );
+ dc = sqlite3OsDeviceCharacteristics(pPager->fd);
nSector = pPager->sectorSize;
szPage = pPager->pageSize;
- }
- assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
- assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
-
- if( !fd->pMethods ||
- (dc & (SQLITE_IOCAP_ATOMIC|(szPage>>8)) && nSector<=szPage) ){
- return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
+ assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+ assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+ if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
+ return 0;
+ }
}
- return 0;
+
+ return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
}
#endif
/*
-** This function should be called when an error occurs within the pager
-** code. The first argument is a pointer to the pager structure, the
-** second the error-code about to be returned by a pager API function.
-** The value returned is a copy of the second argument to this function.
+** This function should be called when an IOERR, CORRUPT or FULL error
+** may have occured. The first argument is a pointer to the pager
+** structure, the second the error-code about to be returned by a pager
+** API function. The value returned is a copy of the second argument
+** to this function.
**
** If the second argument is SQLITE_IOERR, SQLITE_CORRUPT, or SQLITE_FULL
** the error becomes persistent. Until the persisten error is cleared,
** cannot be trusted. This state can be cleared by completely discarding
** the contents of the pager-cache. If a transaction was active when
** the persistent error occured, then the rollback journal may need
-** to be replayed.
+** to be replayed to restore the contents of the database file (as if
+** it were a hot-journal).
*/
static void pager_unlock(Pager *pPager);
static int pager_error(Pager *pPager, int 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 supplied by the caller.
+** This function attempts to read a master journal file name from the
+** end of the file and, if successful, copies it into memory supplied
+** by the caller. See comments above writeMasterJournal() for the format
+** used to store a master journal file name at the end of a journal file.
**
** zMaster must point to a buffer of at least nMaster bytes allocated by
** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
** nul-terminator), then this is handled as if no master journal name
** were present in the journal.
**
-** If no master journal file name is present zMaster[0] is set to 0 and
-** SQLITE_OK returned.
+** If a master journal file name is present at the end of the journal
+** file, then it is copied into the buffer pointed to by zMaster. A
+** nul-terminator byte is appended to the buffer following the master
+** journal file name.
+**
+** If it is determined that no master journal file name is present
+** zMaster[0] is set to 0 and SQLITE_OK returned.
+**
+** If an error occurs while reading from the journal file, an SQLite
+** error code is returned.
*/
static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){
- int rc;
- u32 len;
- i64 szJ;
- u32 cksum;
- u32 u; /* Unsigned loop counter */
- unsigned char aMagic[8]; /* A buffer to hold the magic header */
-
+ int rc; /* Return code */
+ u32 len; /* Length in bytes of master journal name */
+ i64 szJ; /* Total size in bytes of journal file pJrnl */
+ u32 cksum; /* MJ checksum value read from journal */
+ u32 u; /* Unsigned loop counter */
+ unsigned char aMagic[8]; /* A buffer to hold the magic header */
zMaster[0] = '\0';
- rc = sqlite3OsFileSize(pJrnl, &szJ);
- if( rc!=SQLITE_OK || szJ<16 ) return rc;
-
- rc = read32bits(pJrnl, szJ-16, &len);
- if( rc!=SQLITE_OK ) return rc;
-
- if( len>=nMaster ){
- return SQLITE_OK;
- }
-
- rc = read32bits(pJrnl, szJ-12, &cksum);
- if( rc!=SQLITE_OK ) return rc;
-
- rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8);
- if( rc!=SQLITE_OK || memcmp(aMagic, aJournalMagic, 8) ) return rc;
-
- rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len);
- if( rc!=SQLITE_OK ){
+ if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
+ || szJ<16
+ || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
+ || len>=nMaster
+ || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
+ || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
+ || memcmp(aMagic, aJournalMagic, 8)
+ || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len))
+ ){
return rc;
}
- zMaster[len] = '\0';
/* See if the checksum matches the master journal name */
for(u=0; u<len; u++){
cksum -= zMaster[u];
- }
+ }
if( cksum ){
/* If the checksum doesn't add up, then one or more of the disk sectors
** containing the master journal filename is corrupted. This means
** definitely roll back, so just return SQLITE_OK and report a (nul)
** master-journal filename.
*/
- zMaster[0] = '\0';
+ len = 0;
}
+ zMaster[len] = '\0';
return SQLITE_OK;
}
/*
-** Seek the journal file descriptor to the next sector boundary where a
-** journal header may be read or written. Pager.journalOff is updated with
-** the new seek offset.
+** Return the offset of the sector boundary at or immediately
+** following the value in pPager->journalOff, assuming a sector
+** size of pPager->sectorSize bytes.
**
** i.e for a sector size of 512:
**
-** Input Offset Output Offset
-** ---------------------------------------
-** 0 0
-** 512 512
-** 100 512
-** 2000 2048
+** Pager.journalOff Return value
+** ---------------------------------------
+** 0 0
+** 512 512
+** 100 512
+** 2000 2048
**
*/
static i64 journalHdrOffset(Pager *pPager){
assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
return offset;
}
-static void seekJournalHdr(Pager *pPager){
- pPager->journalOff = journalHdrOffset(pPager);
-}
/*
-** Write zeros over the header of the journal file. This has the
-** effect of invalidating the journal file and committing the
-** transaction.
+** The journal file must be open when this function is called.
+**
+** This function is a no-op if the journal file has not been written to
+** within the current transaction (i.e. if Pager.journalOff==0).
+**
+** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
+** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
+** zero the 28-byte header at the start of the journal file. In either case,
+** if the pager is not in no-sync mode, sync the journal file immediately
+** after writing or truncating it.
+**
+** If Pager.journalSizeLimit is set to a positive, non-zero value, and
+** following the truncation or zeroing described above the size of the
+** journal file in bytes is larger than this value, then truncate the
+** journal file to Pager.journalSizeLimit bytes. The journal file does
+** not need to be synced following this operation.
+**
+** If an IO error occurs, abandon processing and return the IO error code.
+** Otherwise, return SQLITE_OK.
*/
static int zeroJournalHdr(Pager *pPager, int doTruncate){
- int rc = SQLITE_OK;
- static const char zeroHdr[28] = {0};
-
+ int rc = SQLITE_OK; /* Return code */
+ assert( isOpen(pPager->jfd) );
if( pPager->journalOff ){
- i64 iLimit = pPager->journalSizeLimit;
+ const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */
IOTRACE(("JZEROHDR %p\n", pPager))
if( doTruncate || iLimit==0 ){
rc = sqlite3OsTruncate(pPager->jfd, 0);
}else{
+ static const char zeroHdr[28] = {0};
rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
}
if( rc==SQLITE_OK && !pPager->noSync ){
** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
*/
static int writeJournalHdr(Pager *pPager){
- int rc = SQLITE_OK;
- char *zHeader = pPager->pTmpSpace;
- u32 nHeader = pPager->pageSize;
- u32 nWrite;
- int ii;
+ int rc = SQLITE_OK; /* Return code */
+ char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */
+ u32 nHeader = pPager->pageSize; /* Size of buffer pointed to by zHeader */
+ u32 nWrite; /* Bytes of header sector written */
+ int ii; /* Loop counter */
+
+ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
if( nHeader>JOURNAL_HDR_SZ(pPager) ){
nHeader = JOURNAL_HDR_SZ(pPager);
}
- /* If there are active savepoints and any of them were created since the
- ** most recent journal header was written, update the PagerSavepoint.iHdrOff
- ** fields now.
+ /* If there are active savepoints and any of them were created
+ ** since the most recent journal header was written, update the
+ ** PagerSavepoint.iHdrOffset fields now.
*/
for(ii=0; ii<pPager->nSavepoint; ii++){
if( pPager->aSavepoint[ii].iHdrOffset==0 ){
}
}
- seekJournalHdr(pPager);
- pPager->journalHdr = pPager->journalOff;
-
+ pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
/*
** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
** that garbage data is never appended to the journal file.
*/
- assert(pPager->fd->pMethods||pPager->noSync);
+ assert( isOpen(pPager->fd) || pPager->noSync );
if( (pPager->noSync) || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
|| (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
){
/* The assumed sector size for this process */
put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
+ /* The page size */
+ put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
+
/* Initializing the tail of the buffer is not necessary. Everything
** works find if the following memset() is omitted. But initializing
** the memory prevents valgrind from complaining, so we are willing to
** take the performance hit.
*/
- memset(&zHeader[sizeof(aJournalMagic)+16], 0,
- nHeader-(sizeof(aJournalMagic)+16));
-
- if( pPager->journalHdr==0 ){
- /* The page size */
- put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
- }
-
+ memset(&zHeader[sizeof(aJournalMagic)+20], 0,
+ nHeader-(sizeof(aJournalMagic)+20));
+
+ /* In theory, it is only necessary to write the 28 bytes that the
+ ** journal header consumes to the journal file here. Then increment the
+ ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next
+ ** record is written to the following sector (leaving a gap in the file
+ ** that will be implicitly filled in by the OS).
+ **
+ ** However it has been discovered that on some systems this pattern can
+ ** be significantly slower than contiguously writing data to the file,
+ ** even if that means explicitly writing data to the block of
+ ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
+ ** is done.
+ **
+ ** The loop is required here in case the sector-size is larger than the
+ ** database page size. Since the zHeader buffer is only Pager.pageSize
+ ** bytes in size, more than one call to sqlite3OsWrite() may be required
+ ** to populate the entire journal header sector.
+ */
for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
** The journal file must be open when this is called. A journal header file
** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
** file. The current location in the journal file is given by
-** pPager->journalOff. See comments above function writeJournalHdr() for
+** pPager->journalOff. 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
+** If the header is read successfully, *pNRec is set to the number of
+** page records following this header and *pDbSize is set to the size of the
** database before the transaction began, in pages. Also, pPager->cksumInit
** is set to the value read from the journal header. SQLITE_OK is returned
** in this case.
**
** If the journal header file appears to be corrupted, SQLITE_DONE is
-** returned and *nRec and *dbSize are undefined. If JOURNAL_HDR_SZ bytes
+** returned and *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes
** cannot be read from the journal file an error code is returned.
*/
static int readJournalHdr(
- Pager *pPager,
- i64 journalSize,
- u32 *pNRec,
- u32 *pDbSize
+ Pager *pPager, /* Pager object */
+ i64 journalSize, /* Size of the open journal file in bytes */
+ u32 *pNRec, /* OUT: Value read from the nRec field */
+ u32 *pDbSize /* OUT: Value of original database size field */
){
- int rc;
- unsigned char aMagic[8]; /* A buffer to hold the magic header */
- i64 jrnlOff;
- u32 iPageSize;
- u32 iSectorSize;
+ int rc; /* Return code */
+ unsigned char aMagic[8]; /* A buffer to hold the magic header */
+ i64 iHdrOff; /* Offset of journal header being read */
- seekJournalHdr(pPager);
+ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
+
+ /* Advance Pager.journalOff to the start of the next sector. If the
+ ** journal file is too small for there to be a header stored at this
+ ** point, return SQLITE_DONE.
+ */
+ pPager->journalOff = journalHdrOffset(pPager);
if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
return SQLITE_DONE;
}
- jrnlOff = pPager->journalOff;
-
- rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), jrnlOff);
- if( rc ) return rc;
- jrnlOff += sizeof(aMagic);
+ iHdrOff = pPager->journalOff;
+ /* Read in the first 8 bytes of the journal header. If they do not match
+ ** the magic string found at the start of each journal header, return
+ ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
+ ** proceed.
+ */
+ rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
+ if( rc ){
+ return rc;
+ }
if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
return SQLITE_DONE;
}
- rc = read32bits(pPager->jfd, jrnlOff, pNRec);
- if( rc ) return rc;
-
- rc = read32bits(pPager->jfd, jrnlOff+4, &pPager->cksumInit);
- if( rc ) return rc;
-
- rc = read32bits(pPager->jfd, jrnlOff+8, pDbSize);
- if( rc ) return rc;
+ /* Read the first three 32-bit fields of the journal header: The nRec
+ ** field, the checksum-initializer and the database size at the start
+ ** of the transaction. Return an error code if anything goes wrong.
+ */
+ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
+ || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
+ || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
+ ){
+ return rc;
+ }
if( pPager->journalOff==0 ){
- rc = read32bits(pPager->jfd, jrnlOff+16, &iPageSize);
- if( rc ) return rc;
+ u32 iPageSize; /* Page-size field of journal header */
+ u32 iSectorSize; /* Sector-size field of journal header */
+ u16 iPageSize16; /* Copy of iPageSize in 16-bit variable */
+
+ /* Read the page-size and sector-size journal header fields. */
+ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
+ || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
+ ){
+ return rc;
+ }
- if( iPageSize<512
- || iPageSize>SQLITE_MAX_PAGE_SIZE
- || ((iPageSize-1)&iPageSize)!=0
+ /* Check that the values read from the page-size and sector-size fields
+ ** are within range. To be 'in range', both values need to be a power
+ ** of two greater than or equal to 512, and not greater than their
+ ** respective compile time maximum limits.
+ */
+ if( iPageSize<512 || iSectorSize<512
+ || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
+ || ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0
){
- /* If the page-size in the journal-header is invalid, then the process
- ** that wrote the journal-header must have crashed before the header
- ** was synced. In this case stop reading the journal file here.
+ /* If the either the page-size or sector-size in the journal-header is
+ ** invalid, then the process that wrote the journal-header must have
+ ** crashed before the header was synced. In this case stop reading
+ ** the journal file here.
*/
- rc = SQLITE_DONE;
- }else{
- u16 pagesize = (u16)iPageSize;
- rc = sqlite3PagerSetPagesize(pPager, &pagesize);
- assert( rc!=SQLITE_OK || pagesize==(u16)iPageSize );
+ return SQLITE_DONE;
}
- if( rc ) return rc;
-
+
+ /* Update the page-size to match the value read from the journal.
+ ** Use a testcase() macro to make sure that malloc failure within
+ ** PagerSetPagesize() is tested.
+ */
+ iPageSize16 = (u16)iPageSize;
+ rc = sqlite3PagerSetPagesize(pPager, &iPageSize16);
+ testcase( rc!=SQLITE_OK );
+ assert( rc!=SQLITE_OK || iPageSize16==(u16)iPageSize );
+
/* Update the assumed sector-size to match the value used by
** the process that created this journal. If this journal was
** created by a process other than this one, then this routine
** is being called from within pager_playback(). The local value
** of Pager.sectorSize is restored at the end of that routine.
*/
- rc = read32bits(pPager->jfd, jrnlOff+12, &iSectorSize);
- if( rc ) return rc;
- if( (iSectorSize&(iSectorSize-1))
- || iSectorSize<512
- || iSectorSize>MAX_SECTOR_SIZE
- ){
- return SQLITE_DONE;
- }
pPager->sectorSize = iSectorSize;
}
pPager->journalOff += JOURNAL_HDR_SZ(pPager);
- return SQLITE_OK;
+ return rc;
}
** 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[].
+** + 4 bytes: PAGER_MJ_PGNO.
+** + N bytes: Master journal filename in utf-8.
+** + 4 bytes: N (length of master journal name in bytes, no nul-terminator).
+** + 4 bytes: Master journal name checksum.
+** + 8 bytes: aJournalMagic[].
**
** The master journal page checksum is the sum of the bytes in the master
-** journal name.
+** journal name, where each byte is interpreted as a signed 8-bit integer.
**
** If zMaster is a NULL pointer (occurs for a single database transaction),
** this call is a no-op.
*/
static int writeMasterJournal(Pager *pPager, const char *zMaster){
- int rc;
- int len;
- int i;
- i64 jrnlOff;
- i64 jrnlSize;
- u32 cksum = 0;
- char zBuf[sizeof(aJournalMagic)+2*4];
-
- if( !zMaster || pPager->setMaster ) return SQLITE_OK;
+ int rc; /* Return code */
+ int nMaster; /* Length of string zMaster */
+ i64 iHdrOff; /* Offset of header in journal file */
+ i64 jrnlSize; /* Size of journal file on disk */
+ u32 cksum = 0; /* Checksum of string zMaster */
+
+ assert( isOpen(pPager->jfd) );
+ assert( !pPager->setMaster );
+
+ if( !zMaster ) return SQLITE_OK;
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ) return SQLITE_OK;
pPager->setMaster = 1;
- len = sqlite3Strlen30(zMaster);
- for(i=0; i<len; i++){
- cksum += zMaster[i];
+ /* Calculate the length in bytes and the checksum of zMaster */
+ for(nMaster=0; zMaster[nMaster]; nMaster++){
+ cksum += zMaster[nMaster];
}
/* If in full-sync mode, advance to the next disk sector before writing
** the journal has already been synced.
*/
if( pPager->fullSync ){
- seekJournalHdr(pPager);
+ pPager->journalOff = journalHdrOffset(pPager);
}
- jrnlOff = pPager->journalOff;
- pPager->journalOff += (len+20);
-
- rc = write32bits(pPager->jfd, jrnlOff, PAGER_MJ_PGNO(pPager));
- if( rc!=SQLITE_OK ) return rc;
- jrnlOff += 4;
+ iHdrOff = pPager->journalOff;
- rc = sqlite3OsWrite(pPager->jfd, zMaster, len, jrnlOff);
- if( rc!=SQLITE_OK ) return rc;
- jrnlOff += len;
-
- put32bits(zBuf, len);
- put32bits(&zBuf[4], cksum);
- memcpy(&zBuf[8], aJournalMagic, sizeof(aJournalMagic));
- rc = sqlite3OsWrite(pPager->jfd, zBuf, 8+sizeof(aJournalMagic), jrnlOff);
- jrnlOff += 8+sizeof(aJournalMagic);
+ /* Write the master journal data to the end of the journal file. If
+ ** an error occurs, return the error code to the caller.
+ */
+ if( (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager)))
+ || (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4))
+ || (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster))
+ || (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum))
+ || (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, iHdrOff+4+nMaster+8))
+ ){
+ return rc;
+ }
+ pPager->journalOff += (nMaster+20);
pPager->needSync = !pPager->noSync;
/* If the pager is in peristent-journal mode, then the physical
** Easiest thing to do in this scenario is to truncate the journal
** file to the required size.
*/
- if( (rc==SQLITE_OK)
- && (rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))==SQLITE_OK
- && jrnlSize>jrnlOff
+ if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
+ && jrnlSize>pPager->journalOff
){
- rc = sqlite3OsTruncate(pPager->jfd, jrnlOff);
+ rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
}
return rc;
}
/*
-** Find a page in the hash table given its page number. Return
-** a pointer to the page or NULL if not found.
+** Find a page in the hash table given its page number. Return
+** a pointer to the page or NULL if the requested page is not
+** already in memory.
*/
static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
- PgHdr *p;
- sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p);
+ PgHdr *p; /* Return value */
+
+ /* It is not possible for a call to PcacheFetch() with createFlag==0 to
+ ** fail, since no attempt to allocate dynamic memory will be made.
+ */
+ (void)sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p);
return p;
}
/*
-** 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.
+** Unless the pager is in error-state, discard all in-memory pages. If
+** the pager is in error-state, then this call is a no-op.
*/
static void pager_reset(Pager *pPager){
- if( pPager->errCode ) return;
- sqlite3PcacheClear(pPager->pPCache);
+ if( SQLITE_OK==pPager->errCode ){
+ sqlite3PcacheClear(pPager->pPCache);
+ }
}
/*
** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
** if it is open and the pager is not in exclusive mode.
*/
-static void releaseAllSavepoint(Pager *pPager){
- int ii;
+static void releaseAllSavepoints(Pager *pPager){
+ int ii; /* Iterator for looping through Pager.aSavepoint */
for(ii=0; ii<pPager->nSavepoint; ii++){
sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
}
sqlite3_free(pPager->aSavepoint);
pPager->aSavepoint = 0;
pPager->nSavepoint = 0;
- pPager->stmtNRec = 0;
+ pPager->nSubRec = 0;
}
/*
-** Set the bit number pgno in the PagerSavepoint.pInSavepoint bitvecs of
-** all open savepoints.
+** Set the bit number pgno in the PagerSavepoint.pInSavepoint
+** bitvecs of all open savepoints. Return SQLITE_OK if successful
+** or SQLITE_NOMEM if a malloc failure occurs.
*/
static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
int ii; /* Loop counter */
PagerSavepoint *p = &pPager->aSavepoint[ii];
if( pgno<=p->nOrig ){
rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
+ testcase( rc==SQLITE_NOMEM );
assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
}
}
}
/*
-** Unlock the database file.
+** Unlock the database file. This function is a no-op if the pager
+** is in exclusive mode.
**
** If the pager is currently in error state, discard the contents of
** the cache and reset the Pager structure internal state. If there is
*/
static void pager_unlock(Pager *pPager){
if( !pPager->exclusiveMode ){
- int rc;
+ int rc; /* Return code */
/* Always close the journal file when dropping the database lock.
** Otherwise, another connection with journal_mode=delete might
** delete the file out from under us.
*/
- if( pPager->journalOpen ){
- sqlite3OsClose(pPager->jfd);
- pPager->journalOpen = 0;
- sqlite3BitvecDestroy(pPager->pInJournal);
- pPager->pInJournal = 0;
- sqlite3BitvecDestroy(pPager->pAlwaysRollback);
- pPager->pAlwaysRollback = 0;
- }
+ sqlite3OsClose(pPager->jfd);
+ sqlite3BitvecDestroy(pPager->pInJournal);
+ pPager->pInJournal = 0;
+ releaseAllSavepoints(pPager);
- rc = osUnlock(pPager->fd, NO_LOCK);
- if( rc ) pPager->errCode = rc;
+ /* If the file is unlocked, somebody else might change it. The
+ ** values stored in Pager.dbSize etc. might become invalid if
+ ** this happens. TODO: Really, this doesn't need to be cleared
+ ** until the change-counter check fails in pagerSharedLock().
+ */
pPager->dbSizeValid = 0;
+
+ rc = osUnlock(pPager->fd, NO_LOCK);
+ if( rc ){
+ pPager->errCode = rc;
+ }
IOTRACE(("UNLOCK %p\n", pPager))
/* If Pager.errCode is set, the contents of the pager cache cannot be
** cache can be discarded and the error code safely cleared.
*/
if( pPager->errCode ){
- if( rc==SQLITE_OK ) pPager->errCode = SQLITE_OK;
+ if( rc==SQLITE_OK ){
+ pPager->errCode = SQLITE_OK;
+ }
pager_reset(pPager);
- releaseAllSavepoint(pPager);
- pPager->journalOff = 0;
- pPager->journalStarted = 0;
- pPager->dbOrigSize = 0;
}
- pPager->state = PAGER_UNLOCK;
pPager->changeCountDone = 0;
+ pPager->state = PAGER_UNLOCK;
}
}
/*
** Execute a rollback if a transaction is active and unlock the
-** database file. If the pager has already entered the error state,
-** do not attempt the rollback.
+** database file.
+**
+** If the pager has already entered the error state, do not attempt
+** the rollback at this time. Instead, pager_unlock() is called. The
+** call to pager_unlock() will discard all in-memory pages, unlock
+** the database file and clear the error state. If this means that
+** there is a hot-journal left in the file-system, the next connection
+** to obtain a shared lock on the pager (which may be this one) will
+** roll it back.
+**
+** If the pager has not already entered the error state, but an IO or
+** malloc error occurs during a rollback, then this will itself cause
+** the pager to enter the error state. Which will be cleared by the
+** call to pager_unlock(), as described above.
*/
-static void pagerUnlockAndRollback(Pager *p){
- if( p->errCode==SQLITE_OK && p->state>=PAGER_RESERVED ){
+static void pagerUnlockAndRollback(Pager *pPager){
+ if( pPager->errCode==SQLITE_OK && pPager->state>=PAGER_RESERVED ){
sqlite3BeginBenignMalloc();
- sqlite3PagerRollback(p);
+ sqlite3PagerRollback(pPager);
sqlite3EndBenignMalloc();
}
- pager_unlock(p);
+ pager_unlock(pPager);
}
/*
-** This routine ends a transaction. A transaction is ended by either
-** a COMMIT or a ROLLBACK.
+** This routine ends a transaction. A transaction is usually ended by
+** either a COMMIT or a ROLLBACK operation. This routine may be called
+** after rollback of a hot-journal, or if an error occurs while opening
+** the journal file or writing the very first journal-header of a
+** database transaction.
+**
+** If the pager is in PAGER_SHARED or PAGER_UNLOCK state when this
+** routine is called, it is a no-op (returns SQLITE_OK).
+**
+** Otherwise, any active savepoints are released.
+**
+** If the journal file is open, then it is "finalized". Once a journal
+** file has been finalized it is not possible to use it to roll back a
+** transaction. Nor will it be considered to be a hot-journal by this
+** or any other database connection. Exactly how a journal is finalized
+** depends on whether or not the pager is running in exclusive mode and
+** the current journal-mode (Pager.journalMode value), as follows:
+**
+** journalMode==MEMORY
+** Journal file descriptor is simply closed. This destroys an
+** in-memory journal.
+**
+** journalMode==TRUNCATE
+** Journal file is truncated to zero bytes in size.
+**
+** journalMode==PERSIST
+** The first 28 bytes of the journal file are zeroed. This invalidates
+** the first journal header in the file, and hence the entire journal
+** file. An invalid journal file cannot be rolled back.
**
-** When this routine is called, the pager has the journal file open and
-** a RESERVED or EXCLUSIVE lock on the database. This routine will release
-** the database lock and acquires a SHARED lock in its place if that is
-** the appropriate thing to do. Release locks usually is appropriate,
-** unless we are in exclusive access mode or unless this is a
-** COMMIT AND BEGIN or ROLLBACK AND BEGIN operation.
+** journalMode==DELETE
+** The journal file is closed and deleted using sqlite3OsDelete().
**
-** The journal file is either deleted or truncated.
+** If the pager is running in exclusive mode, this method of finalizing
+** the journal file is never used. Instead, if the journalMode is
+** DELETE and the pager is in exclusive mode, the method described under
+** journalMode==PERSIST is used instead.
**
-** 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.
+** After the journal is finalized, if running in non-exclusive mode, the
+** pager moves to PAGER_SHARED state (and downgrades the lock on the
+** database file accordingly).
+**
+** If the pager is running in exclusive mode and is in PAGER_SYNCED state,
+** it moves to PAGER_EXCLUSIVE. No locks are downgraded when running in
+** exclusive mode.
+**
+** SQLITE_OK is returned if no error occurs. If an error occurs during
+** any of the IO operations to finalize the journal file or unlock the
+** database then the IO error code is returned to the user. If the
+** operation to finalize the journal file fails, then the code still
+** tries to unlock the database file if not in exclusive mode. If the
+** unlock operation fails as well, then the first error code related
+** to the first error encountered (the journal finalization one) is
+** returned.
*/
static int pager_end_transaction(Pager *pPager, int hasMaster){
- int rc = SQLITE_OK;
- int rc2 = SQLITE_OK;
+ int rc = SQLITE_OK; /* Error code from journal finalization operation */
+ int rc2 = SQLITE_OK; /* Error code from db file unlock operation */
+
if( pPager->state<PAGER_RESERVED ){
return SQLITE_OK;
}
- releaseAllSavepoint(pPager);
- if( pPager->journalOpen ){
+ releaseAllSavepoints(pPager);
+
+ assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
+ if( isOpen(pPager->jfd) ){
+
+ /* TODO: There's a problem here if a journal-file was opened in MEMORY
+ ** mode and then the journal-mode is changed to TRUNCATE or PERSIST
+ ** during the transaction. This code should be changed to assume
+ ** that the journal mode has not changed since the transaction was
+ ** started. And the sqlite3PagerJournalMode() function should be
+ ** changed to make sure that this is the case too.
+ */
+
+ /* Finalize the journal file. */
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
int isMemoryJournal = sqlite3IsMemJournal(pPager->jfd);
sqlite3OsClose(pPager->jfd);
- pPager->journalOpen = 0;
if( !isMemoryJournal ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
}else{
assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE || rc );
sqlite3OsClose(pPager->jfd);
- pPager->journalOpen = 0;
if( rc==SQLITE_OK && !pPager->tempFile ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
}
- sqlite3BitvecDestroy(pPager->pInJournal);
- pPager->pInJournal = 0;
- sqlite3BitvecDestroy(pPager->pAlwaysRollback);
- pPager->pAlwaysRollback = 0;
+
#ifdef SQLITE_CHECK_PAGES
sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
#endif
+
sqlite3PcacheCleanAll(pPager->pPCache);
- pPager->dirtyCache = 0;
+ sqlite3BitvecDestroy(pPager->pInJournal);
+ pPager->pInJournal = 0;
pPager->nRec = 0;
- }else{
- assert( pPager->pInJournal==0 );
}
if( !pPager->exclusiveMode ){
}else if( pPager->state==PAGER_SYNCED ){
pPager->state = PAGER_EXCLUSIVE;
}
- pPager->dbOrigSize = 0;
pPager->setMaster = 0;
pPager->needSync = 0;
- /* lruListSetFirstSynced(pPager); */
+ pPager->dbModified = 0;
+
+ /* TODO: Is this optimal? Why is the db size invalidated here
+ ** when the database file is not unlocked? */
+ pPager->dbOrigSize = 0;
sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
if( !MEMDB ){
pPager->dbSizeValid = 0;
}
- pPager->dbModified = 0;
return (rc==SQLITE_OK?rc2:rc);
}
/*
-** Compute and return a checksum for the page of data.
+** Parameter aData must point to a buffer of pPager->pageSize bytes
+** of data. Compute and return a checksum based ont the contents of the
+** page of data and the current value of pPager->cksumInit.
**
-** This is not a real checksum. It is really just the sum of the
-** random initial value and the page number. We experimented with
-** a checksum of the entire data, but that was found to be too slow.
+** This is not a real checksum. It is really just the sum of the
+** random initial value (pPager->cksumInit) and every 200th byte
+** of the page data, starting with byte offset (pPager->pageSize%200).
+** Each byte is interpreted as an 8-bit unsigned integer.
**
-** 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
+** Changing the formula used to compute this checksum results in an
+** incompatible journal file format.
+**
+** If journal corruption occurs due to a power failure, the most likely
+** scenario is that one end or the other of the record will be changed.
+** It is much less likely that the two ends of the journal record will be
** correct and the middle be corrupt. Thus, this "checksum" scheme,
** though fast and simple, catches the mostly likely kind of corruption.
-**
-** FIX ME: Consider adding every 200th (or so) byte of the data to the
-** checksum. That way if a single page spans 3 or more disk sectors and
-** only the middle sector is corrupt, we will still have a reasonable
-** chance of failing the checksum and thus detecting the problem.
*/
static u32 pager_cksum(Pager *pPager, const u8 *aData){
- u32 cksum = pPager->cksumInit;
- int i = pPager->pageSize-200;
+ u32 cksum = pPager->cksumInit; /* Checksum value to return */
+ int i = pPager->pageSize-200; /* Loop counter */
while( i>0 ){
cksum += aData[i];
i -= 200;
/*
** Read a single page from either the journal file (if isMainJrnl==1) or
** from the sub-journal (if isMainJrnl==0) and playback that page.
-** The page begins at offset *pOffset into the file. The *pOffset
+** The page begins at offset *pOffset into the file. The *pOffset
** value is increased to the start of the next page in the journal.
**
** The isMainJrnl flag is true if this is the main rollback journal and
** false for the statement journal. The main rollback journal uses
** checksums - the statement journal does not.
**
+** If the page number of the page record read from the (sub-)journal file
+** is greater than the current value of Pager.dbSize, then playback is
+** skipped and SQLITE_OK is returned.
+**
** If pDone is not NULL, then it is a record of pages that have already
** been played back. If the page at *pOffset has already been played back
** (if the corresponding pDone bit is set) then skip the playback.
** Make sure the pDone bit corresponding to the *pOffset page is set
** prior to returning.
+**
+** If the page record is successfully read from the (sub-)journal file
+** and played back, then SQLITE_OK is returned. If an IO error occurs
+** while reading the record from the (sub-)journal file or while writing
+** to the database file, then the IO error code is returned. If data
+** is successfully read from the (sub-)journal file but appears to be
+** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
+** two circumstances:
+**
+** * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or
+** * If the record is being rolled back from the main journal file
+** and the checksum field does not match the record content.
+**
+** Neither of these two scenarios are possible during a savepoint rollback.
+**
+** If this is a savepoint rollback, then memory may have to be dynamically
+** allocated by this function. If this is the case and an allocation fails,
+** SQLITE_NOMEM is returned.
*/
static int pager_playback_one_page(
Pager *pPager, /* The pager being played back */
aData = (u8*)pPager->pTmpSpace;
assert( aData ); /* Temp storage must have already been allocated */
+ /* Read the page number and page data from the journal or sub-journal
+ ** file. Return an error code to the caller if an IO error occurs.
+ */
jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
-
rc = read32bits(jfd, *pOffset, &pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(jfd, aData, pPager->pageSize, (*pOffset)+4);
** detect this invalid data (with high probability) and ignore it.
*/
if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
+ assert( !isSavepnt );
return SQLITE_DONE;
}
if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
return SQLITE_DONE;
}
}
+
if( pDone && (rc = sqlite3BitvecSet(pDone, pgno)) ){
return rc;
}
));
if( (pPager->state>=PAGER_EXCLUSIVE)
&& (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC))
- && (pPager->fd->pMethods)
+ && isOpen(pPager->fd)
){
i64 ofst = (pgno-1)*(i64)pPager->pageSize;
rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize, ofst);
if( pPager->xReiniter ){
pPager->xReiniter(pPg);
}
- if( isMainJrnl && (!isSavepnt || pPager->journalOff<=pPager->journalHdr) ){
+ if( isMainJrnl && (!isSavepnt || *pOffset<=pPager->journalHdr) ){
/* If the contents of this page were just restored from the main
** journal file, then its content must be as they were when the
** transaction was first opened. In this case we can mark the page
** Argument zMaster may point to Pager.pTmpSpace. So that buffer is not
** available for use within this function.
**
+** When a master journal file is created, it is populated with the names
+** of all of its child journals, one after another, formatted as utf-8
+** encoded text. The end of each child journal file is marked with a
+** nul-terminator byte (0x00). i.e. the entire contents of a master journal
+** file for a transaction involving two databases might be:
+**
+** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
+**
+** A master journal file may only be deleted once all of its child
+** journals have been rolled back.
**
-** 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.
+** This function reads the contents of the master-journal file into
+** memory and loops through each of the child journal names. For
+** each child journal, it checks if:
+**
+** * if the child journal exists, and if so
+** * if the child journal contains a reference to master journal
+** file zMaster
+**
+** If a child journal can be found that matches both of the criteria
+** above, this function returns without doing anything. Otherwise, if
+** no such child journal can be found, file zMaster is deleted from
+** the file-system using sqlite3OsDelete().
+**
+** If an IO error within this function, an error code is returned. This
+** function allocates memory by calling sqlite3Malloc(). If an allocation
+** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors
+** occur, SQLITE_OK is returned.
+**
+** TODO: This function allocates a single block of memory to load
+** the entire contents of the master journal file. This could be
+** a couple of kilobytes or so - potentially larger than the page
+** size.
*/
static int pager_delmaster(Pager *pPager, const char *zMaster){
sqlite3_vfs *pVfs = pPager->pVfs;
- int rc;
- int master_open = 0;
- sqlite3_file *pMaster;
- sqlite3_file *pJournal;
+ int rc; /* Return code */
+ sqlite3_file *pMaster; /* Malloc'd master-journal file descriptor */
+ sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */
char *zMasterJournal = 0; /* Contents of master journal file */
i64 nMasterJournal; /* Size of master journal file */
rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0);
}
if( rc!=SQLITE_OK ) goto delmaster_out;
- master_open = 1;
rc = sqlite3OsFileSize(pMaster, &nMasterJournal);
if( rc!=SQLITE_OK ) goto delmaster_out;
if( nMasterJournal>0 ){
char *zJournal;
char *zMasterPtr = 0;
- int nMasterPtr = pPager->pVfs->mxPathname+1;
+ int nMasterPtr = pVfs->mxPathname+1;
/* Load the entire master journal file into space obtained from
** sqlite3_malloc() and pointed to by zMasterJournal.
if( zMasterJournal ){
sqlite3_free(zMasterJournal);
}
- if( master_open ){
+ if( pMaster ){
sqlite3OsClose(pMaster);
+ assert( !isOpen(pJournal) );
}
sqlite3_free(pMaster);
return rc;
/*
-** If the main database file is open and an exclusive lock is held,
-** truncate the main file of the given pager to the specified number
-** of pages.
-**
-** It might might be the case that the file on disk is smaller than nPage.
-** This can happen, for example, if we are in the middle of a transaction
-** which has extended the file size and the new pages are still all held
-** in cache, then an INSERT or UPDATE does a statement rollback. Some
-** operating system implementations can get confused if you try to
-** truncate a file to some size that is larger than it currently is,
-** so detect this case and write a single zero byte to the end of the new
-** file instead.
+** This function is used to change the actual size of the database
+** file in the file-system. This only happens when committing a transaction,
+** or rolling back a transaction (including rolling back a hot-journal).
+**
+** If the main database file is not open, or an exclusive lock is not
+** held, this function is a no-op. Otherwise, the size of the file is
+** changed to nPage pages (nPage*pPager->pageSize bytes). If the file
+** on disk is currently larger than nPage pages, then use the VFS
+** xTruncate() method to truncate it.
+**
+** Or, it might might be the case that the file on disk is smaller than
+** nPage pages. Some operating system implementations can get confused if
+** you try to truncate a file to some size that is larger than it
+** currently is, so detect this case and write a single zero byte to
+** the end of the new file instead.
+**
+** If successful, return SQLITE_OK. If an IO error occurs while modifying
+** the database file, return the error code to the caller.
*/
static int pager_truncate(Pager *pPager, Pgno nPage){
int rc = SQLITE_OK;
- if( pPager->state>=PAGER_EXCLUSIVE && pPager->fd->pMethods ){
+ if( pPager->state>=PAGER_EXCLUSIVE && isOpen(pPager->fd) ){
i64 currentSize, newSize;
+ /* TODO: Is it safe to use Pager.dbFileSize here? */
rc = sqlite3OsFileSize(pPager->fd, ¤tSize);
newSize = pPager->pageSize*(i64)nPage;
if( rc==SQLITE_OK && currentSize!=newSize ){
}
/*
-** Set the sectorSize for the given pager.
+** Set the value of the Pager.sectorSize variable for the given
+** pager based on the value returned by the xSectorSize method
+** of the open database file. The sector size will be used used
+** to determine the size and alignment of journal header and
+** master journal pointers within created journal files.
**
-** The sector size is at least as big as the sector size reported
-** by sqlite3OsSectorSize(). The minimum sector size is 512.
+** For temporary files the effective sector size is always 512 bytes.
+**
+** Otherwise, for non-temporary files, the effective sector size is
+** the value returned by the xSectorSize() method rounded up to 512 if
+** it is less than 512, or rounded down to MAX_SECTOR_SIZE if it
+** is greater than MAX_SECTOR_SIZE.
*/
static void setSectorSize(Pager *pPager){
- assert(pPager->fd->pMethods||pPager->tempFile);
+ assert( isOpen(pPager->fd) || pPager->tempFile );
+
if( !pPager->tempFile ){
/* Sector size doesn't matter for temporary files. Also, the file
- ** may not have been opened yet, in whcih case the OsSectorSize()
+ ** may not have been opened yet, in which case the OsSectorSize()
** call will segfault.
*/
pPager->sectorSize = sqlite3OsSectorSize(pPager->fd);
pPager->sectorSize = 512;
}
if( pPager->sectorSize>MAX_SECTOR_SIZE ){
+ assert( MAX_SECTOR_SIZE>=512 );
pPager->sectorSize = MAX_SECTOR_SIZE;
}
}
/* Figure out how many records are in the journal. Abort early if
** the journal is empty.
*/
- assert( pPager->journalOpen );
+ assert( isOpen(pPager->jfd) );
rc = sqlite3OsFileSize(pPager->jfd, &szJ);
if( rc!=SQLITE_OK || szJ==0 ){
goto end_playback;
** If a master journal file name is specified, but the file is not
** present on disk, then the journal is not hot and does not need to be
** played back.
+ **
+ ** TODO: Technically the following is an error because it assumes that
+ ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
+ ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
+ ** mxPathname is 512, which is the same as the minimum allowable value
+ ** for pageSize.
*/
zMaster = pPager->pTmpSpace;
rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
}
pPager->journalOff = 0;
- /* This loop terminates either when the readJournalHdr() call returns
- ** SQLITE_DONE or an IO error occurs. */
+ /* This loop terminates either when a readJournalHdr() or
+ ** pager_playback_one_page() call returns SQLITE_DONE or an IO error
+ ** occurs.
+ */
while( 1 ){
/* Read the next journal header from the journal file. If there are
pPager->dbSize = mxPg;
}
- /* Copy original pages out of the journal and back into the database file.
+ /* Copy original pages out of the journal and back into the
+ ** database file and/or page cache.
*/
for(u=0; u<nRec; u++){
rc = pager_playback_one_page(pPager, 1, &pPager->journalOff, 0, 0);
if( rc==SQLITE_OK ){
zMaster = pPager->pTmpSpace;
rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
+ testcase( rc!=SQLITE_OK );
}
if( rc==SQLITE_OK ){
rc = pager_end_transaction(pPager, zMaster[0]!='\0');
+ testcase( rc!=SQLITE_OK );
}
if( rc==SQLITE_OK && zMaster[0] && res ){
/* If there was a master journal and this routine will return success,
** see if it is possible to delete the master journal.
*/
rc = pager_delmaster(pPager, zMaster);
+ testcase( rc!=SQLITE_OK );
}
/* The Pager.sectorSize variable may have been updated while rolling
}
/*
-** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
-** the entire master journal file.
+** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
+** the entire master journal file. The case pSavepoint==NULL occurs when
+** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction
+** savepoint.
+**
+** When pSavepoint is not NULL (meaning a non-transaction savepoint is
+** being rolled back), then the rollback consists of up to three stages,
+** performed in the order specified:
+**
+** * Pages are played back from the main journal starting at byte
+** offset PagerSavepoint.iOffset and continuing to
+** PagerSavepoint.iHdrOffset, or to the end of the main journal
+** file if PagerSavepoint.iHdrOffset is zero.
+**
+** * If PagerSavepoint.iHdrOffset is not zero, then pages are played
+** back starting from the journal header immediately following
+** PagerSavepoint.iHdrOffset to the end of the main journal file.
+**
+** * Pages are then played back from the sub-journal file, starting
+** with the PagerSavepoint.iSubRec and continuing to the end of
+** the journal file.
**
-** The case pSavepoint==NULL occurs when a ROLLBACK TO command is invoked
-** on a SAVEPOINT that is a transaction savepoint.
+** Throughout the rollback process, each time a page is rolled back, the
+** corresponding bit is set in a bitvec structure (variable pDone in the
+** implementation below). This is used to ensure that a page is only
+** rolled back the first time it is encountered in either journal.
+**
+** If pSavepoint is NULL, then pages are only played back from the main
+** journal file. There is no need for a bitvec in this case.
+**
+** In either case, before playback commences the Pager.dbSize variable
+** is reset to the value that it held at the start of the savepoint
+** (or transaction). No page with a page-number greater than this value
+** is played back. If one is encountered it is simply skipped.
*/
static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
i64 szJ; /* Effective size of the main journal */
i64 iHdrOff; /* End of first segment of main-journal records */
- Pgno ii; /* Loop counter */
int rc = SQLITE_OK; /* Return code */
Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */
+ assert( pPager->state>=PAGER_SHARED );
+
/* Allocate a bitvec to use to store the set of pages rolled back */
if( pSavepoint ){
pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
}
}
- /* Truncate the database back to the size it was before the
- ** savepoint being reverted was opened.
+ /* Set the database size back to the value it was before the savepoint
+ ** being reverted was opened.
*/
pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
- assert( pPager->state>=PAGER_SHARED );
/* Use pPager->journalOff as the effective size of the main rollback
** journal. The actual file might be larger than this in
pPager->journalOff = pSavepoint->iOffset;
while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
rc = pager_playback_one_page(pPager, 1, &pPager->journalOff, 1, pDone);
- assert( rc!=SQLITE_DONE );
}
+ assert( rc!=SQLITE_DONE );
}else{
pPager->journalOff = 0;
}
** continue adding pages rolled back to pDone.
*/
while( rc==SQLITE_OK && pPager->journalOff<szJ ){
+ u32 ii; /* Loop counter */
u32 nJRec = 0; /* Number of Journal Records */
u32 dummy;
rc = readJournalHdr(pPager, szJ, &nJRec, &dummy);
}
for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
rc = pager_playback_one_page(pPager, 1, &pPager->journalOff, 1, pDone);
- assert( rc!=SQLITE_DONE );
}
+ assert( rc!=SQLITE_DONE );
}
assert( rc!=SQLITE_OK || pPager->journalOff==szJ );
** will be skipped. Out-of-range pages are also skipped.
*/
if( pSavepoint ){
+ u32 ii; /* Loop counter */
i64 offset = pSavepoint->iSubRec*(4+pPager->pageSize);
- for(ii=pSavepoint->iSubRec; rc==SQLITE_OK&&ii<(u32)pPager->stmtNRec; ii++){
- assert( offset == ii*(4+pPager->pageSize) );
+ for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
+ assert( offset==ii*(4+pPager->pageSize) );
rc = pager_playback_one_page(pPager, 0, &offset, 1, pDone);
- assert( rc!=SQLITE_DONE );
}
+ assert( rc!=SQLITE_DONE );
}
sqlite3BitvecDestroy(pDone);
#endif
/*
-** Open a temporary file.
+** Open a temporary file.
**
-** Write the file descriptor into *fd. Return SQLITE_OK on success or some
-** other error code if we fail. The OS will automatically delete the temporary
-** file when it is closed.
+** Write the file descriptor into *pFile. Return SQLITE_OK on success
+** or some other error code if we fail. The OS will automatically
+** delete the temporary file when it is closed.
+**
+** The flags passed to the VFS layer xOpen() call are those specified
+** by parameter vfsFlags ORed with the following:
+**
+** SQLITE_OPEN_READWRITE
+** SQLITE_OPEN_CREATE
+** SQLITE_OPEN_EXCLUSIVE
+** SQLITE_OPEN_DELETEONCLOSE
*/
-static int sqlite3PagerOpentemp(
+static int pagerOpentemp(
Pager *pPager, /* The pager object */
sqlite3_file *pFile, /* Write the file descriptor here */
int vfsFlags /* Flags passed through to the VFS */
){
- int rc;
+ int rc; /* Return code */
#ifdef SQLITE_TEST
sqlite3_opentemp_count++; /* Used for testing and analysis only */
vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
- assert( rc!=SQLITE_OK || pFile->pMethods );
+ assert( rc!=SQLITE_OK || isOpen(pFile) );
return rc;
}
static int pagerStress(void *,PgHdr *);
/*
-** Create a new page cache and put a pointer to the page cache in *ppPager.
-** The file to be cached need not exist. The file is not locked until
-** the first call to sqlite3PagerGet() and is only held open until the
-** last page is released using sqlite3PagerUnref().
+** Allocate and initialize a new Pager object and put a pointer to it
+** in *ppPager. The pager should eventually be freed by passing it
+** to sqlite3PagerClose().
**
+** The zFilename argument is the path to the database file to open.
** If zFilename is NULL then a randomly-named temporary file is created
-** and used as the file to be cached. The file will be deleted
-** automatically when it is closed.
+** and used as the file to be cached. Temporary files are be deleted
+** automatically when they are closed. If zFilename is ":memory:" then
+** all information is held in cache. It is never written to disk.
+** This can be used to implement an in-memory database.
+**
+** The nExtra parameter specifies the number of bytes of space allocated
+** along with each page reference. This space is available to the user
+** via the sqlite3PagerGetExtra() API.
**
-** If zFilename is ":memory:" then all information is held in cache.
-** It is never written to disk. This can be used to implement an
-** in-memory database.
+** The flags argument is used to specify properties that affect the
+** operation of the pager. It should be passed some bitwise combination
+** of the PAGER_OMIT_JOURNAL and PAGER_NO_READLOCK flags.
+**
+** The vfsFlags parameter is a bitmask to pass to the flags parameter
+** of the xOpen() method of the supplied VFS when opening files.
+**
+** If the pager object is allocated and the specified file opened
+** successfully, SQLITE_OK is returned and *ppPager set to point to
+** the new pager object. If an error occurs, *ppPager is set to NULL
+** and error code returned. This function may return SQLITE_NOMEM
+** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or
+** various SQLITE_IO_XXX errors.
*/
int sqlite3PagerOpen(
sqlite3_vfs *pVfs, /* The virtual file system to use */
- Pager **ppPager, /* Return the Pager structure here */
+ Pager **ppPager, /* OUT: Return the Pager structure here */
const char *zFilename, /* Name of the database file to open */
int nExtra, /* Extra bytes append to each in-memory page */
int flags, /* flags controlling this file */
int vfsFlags /* flags passed through to sqlite3_vfs.xOpen() */
){
u8 *pPtr;
- Pager *pPager = 0;
- int rc = SQLITE_OK;
- int i;
- int tempFile = 0;
- int memDb = 0;
- int readOnly = 0;
- int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
- int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
- int journalFileSize;
- int pcacheSize = sqlite3PcacheSize();
- int szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;
- char *zPathname = 0;
- int nPathname = 0;
-
+ Pager *pPager = 0; /* Pager object to allocate and return */
+ int rc = SQLITE_OK; /* Return code */
+ int tempFile = 0; /* True for temp files (incl. in-memory files) */
+ int memDb = 0; /* True if this is an in-memory file */
+ int readOnly = 0; /* True if this is a read-only file */
+ int journalFileSize; /* Bytes to allocate for each journal fd */
+ char *zPathname = 0; /* Full path to database file */
+ int nPathname = 0; /* Number of bytes in zPathname */
+ int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
+ int noReadlock = (flags & PAGER_NO_READLOCK)!=0; /* True to omit read-lock */
+ int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */
+ u16 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */
+
+ /* Figure out how much space is required for each journal file-handle
+ ** (there are two of them, the main journal and the sub-journal). This
+ ** is the maximum space required for an in-memory journal file handle
+ ** and a regular journal file-handle. Note that a "regular journal-handle"
+ ** may be a wrapper capable of caching the first portion of the journal
+ ** file in memory to implement the atomic-write optimization (see
+ ** source file journal.c).
+ */
if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){
journalFileSize = sqlite3JournalSize(pVfs);
}else{
journalFileSize = sqlite3MemJournalSize();
}
- /* The default return is a NULL pointer */
+ /* Set the output variable to NULL in case an error occurs. */
*ppPager = 0;
/* Compute and store the full pathname in an allocated buffer pointed
{
rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
}
+
+ nPathname = sqlite3Strlen30(zPathname);
+ if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
+ /* This branch is taken when the journal path required by
+ ** the database being opened will be more than pVfs->mxPathname
+ ** bytes in length. This means the database cannot be opened,
+ ** as it will not be possible to open the journal file or even
+ ** check for a hot-journal before reading.
+ */
+ rc = SQLITE_CANTOPEN;
+ }
if( rc!=SQLITE_OK ){
sqlite3_free(zPathname);
return rc;
}
- nPathname = sqlite3Strlen30(zPathname);
}
- /* Allocate memory for the pager structure */
- pPager = sqlite3MallocZero(
+ /* Allocate memory for the Pager structure, PCache object, the
+ ** three file descriptors, the database file name and the journal
+ ** file name. The layout in memory is as follows:
+ **
+ ** Pager object (sizeof(Pager) bytes)
+ ** PCache object (sqlite3PcacheSize() bytes)
+ ** Database file handle (pVfs->szOsFile bytes)
+ ** Sub-journal file handle (journalFileSize bytes)
+ ** Main journal file handle (journalFileSize bytes)
+ ** Database file name (nPathname+1 bytes)
+ ** Journal file name (nPathname+8+1 bytes)
+ */
+ pPtr = (u8 *)sqlite3MallocZero(
sizeof(*pPager) + /* Pager structure */
pcacheSize + /* PCache object */
- journalFileSize + /* The journal file structure */
pVfs->szOsFile + /* The main db file */
journalFileSize * 2 + /* The two journal files */
- 3*nPathname + 40 /* zFilename, zDirectory, zJournal */
+ nPathname + 1 + /* zFilename */
+ nPathname + 8 + 1 /* zJournal */
);
- if( !pPager ){
+ if( !pPtr ){
sqlite3_free(zPathname);
return SQLITE_NOMEM;
}
- pPager->pPCache = (PCache *)&pPager[1];
- pPtr = ((u8 *)&pPager[1]) + pcacheSize;
- pPager->vfsFlags = vfsFlags;
- pPager->fd = (sqlite3_file*)&pPtr[pVfs->szOsFile*0];
- pPager->sjfd = (sqlite3_file*)&pPtr[pVfs->szOsFile];
- pPager->jfd = (sqlite3_file*)&pPtr[pVfs->szOsFile+journalFileSize];
- pPager->zFilename = (char*)&pPtr[pVfs->szOsFile+2*journalFileSize];
- pPager->zDirectory = &pPager->zFilename[nPathname+1];
- pPager->zJournal = &pPager->zDirectory[nPathname+1];
- pPager->pVfs = pVfs;
+ pPager = (Pager*)(pPtr);
+ pPager->pPCache = (PCache*)(pPtr += sizeof(*pPager));
+ pPager->fd = (sqlite3_file*)(pPtr += pcacheSize);
+ pPager->sjfd = (sqlite3_file*)(pPtr += pVfs->szOsFile);
+ pPager->jfd = (sqlite3_file*)(pPtr += journalFileSize);
+ pPager->zFilename = (char*)(pPtr += journalFileSize);
+
+ /* Fill in the Pager.zFilename and Pager.zJournal buffers, if required. */
if( zPathname ){
- memcpy(pPager->zFilename, zPathname, nPathname+1);
+ pPager->zJournal = (char*)(pPtr += nPathname + 1);
+ memcpy(pPager->zFilename, zPathname, nPathname);
+ memcpy(pPager->zJournal, zPathname, nPathname);
+ memcpy(&pPager->zJournal[nPathname], "-journal", 8);
sqlite3_free(zPathname);
}
+ pPager->pVfs = pVfs;
+ pPager->vfsFlags = vfsFlags;
/* Open the pager file.
*/
if( zFilename && zFilename[0] && !memDb ){
- if( nPathname>(pVfs->mxPathname - (int)sizeof("-journal")) ){
- rc = SQLITE_CANTOPEN;
- }else{
- int fout = 0;
- rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd,
- pPager->vfsFlags, &fout);
- readOnly = (fout&SQLITE_OPEN_READONLY);
-
- /* If the file was successfully opened for read/write access,
- ** choose a default page size in case we have to create the
- ** database file. The default page size is the maximum of:
- **
- ** + SQLITE_DEFAULT_PAGE_SIZE,
- ** + The value returned by sqlite3OsSectorSize()
- ** + The largest page size that can be written atomically.
- */
- if( rc==SQLITE_OK && !readOnly ){
- setSectorSize(pPager);
- if( szPageDflt<pPager->sectorSize ){
- szPageDflt = pPager->sectorSize;
- }
+ int fout = 0; /* VFS flags returned by xOpen() */
+ rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
+ readOnly = (fout&SQLITE_OPEN_READONLY);
+
+ /* If the file was successfully opened for read/write access,
+ ** choose a default page size in case we have to create the
+ ** database file. The default page size is the maximum of:
+ **
+ ** + SQLITE_DEFAULT_PAGE_SIZE,
+ ** + The value returned by sqlite3OsSectorSize()
+ ** + The largest page size that can be written atomically.
+ */
+ if( rc==SQLITE_OK && !readOnly ){
+ setSectorSize(pPager);
+ if( szPageDflt<pPager->sectorSize ){
+ szPageDflt = pPager->sectorSize;
+ }
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
- {
- int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
- int ii;
- assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
- assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
- assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
- for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
- if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ) szPageDflt = ii;
+ {
+ int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+ int ii;
+ assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+ assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+ assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
+ for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
+ if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
+ szPageDflt = ii;
}
}
+ }
#endif
- if( szPageDflt>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
- szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
- }
+ if( szPageDflt>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
+ szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
}
}
}else{
pPager->state = PAGER_EXCLUSIVE;
}
- if( pPager && rc==SQLITE_OK ){
- pPager->pTmpSpace = sqlite3PageMalloc(szPageDflt);
+ /* The following call to PagerSetPagesize() serves to set the value of
+ ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
+ */
+ if( rc==SQLITE_OK ){
+ assert( pPager->memDb==0 );
+ rc = sqlite3PagerSetPagesize(pPager, &szPageDflt);
+ testcase( rc!=SQLITE_OK );
}
- /* If an error occured in either of the blocks above.
- ** Free the Pager structure and close the file.
- ** Since the pager is not allocated there is no need to set
- ** any Pager.errMask variables.
+ /* If an error occured in either of the blocks above, free the
+ ** Pager structure and close the file.
*/
- if( !pPager || !pPager->pTmpSpace ){
+ if( rc!=SQLITE_OK ){
+ assert( !pPager->pTmpSpace );
sqlite3OsClose(pPager->fd);
sqlite3_free(pPager);
- return ((rc==SQLITE_OK)?SQLITE_NOMEM:rc);
+ return rc;
}
+
+ /* Initialize the PCache object. */
nExtra = FORCE_ALIGNMENT(nExtra);
sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
!memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
- /* Fill in Pager.zDirectory[] */
- memcpy(pPager->zDirectory, pPager->zFilename, nPathname+1);
- for(i=sqlite3Strlen30(pPager->zDirectory);
- i>0 && pPager->zDirectory[i-1]!='/'; i--){}
- if( i>0 ) pPager->zDirectory[i-1] = 0;
-
- /* Fill in Pager.zJournal[] */
- if( zPathname ){
- memcpy(pPager->zJournal, pPager->zFilename, nPathname);
- memcpy(&pPager->zJournal[nPathname], "-journal", 9);
- }else{
- pPager->zJournal = 0;
- }
-
- /* pPager->journalOpen = 0; */
pPager->useJournal = (u8)useJournal;
pPager->noReadlock = (noReadlock && readOnly) ?1:0;
/* pPager->stmtOpen = 0; */
/* pPager->stmtInUse = 0; */
/* pPager->nRef = 0; */
pPager->dbSizeValid = (u8)memDb;
- pPager->pageSize = szPageDflt;
/* pPager->stmtSize = 0; */
/* pPager->stmtJSize = 0; */
/* pPager->nPage = 0; */
- pPager->mxPage = 100;
pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
/* pPager->state = PAGER_UNLOCK; */
assert( pPager->state == (tempFile ? PAGER_EXCLUSIVE : PAGER_UNLOCK) );
/* pPager->pLast = 0; */
pPager->nExtra = nExtra;
pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
- assert(pPager->fd->pMethods||tempFile);
+ assert( isOpen(pPager->fd) || tempFile );
setSectorSize(pPager);
if( memDb ){
pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
/*
** Set the busy handler function.
+**
+** The pager invokes the busy-handler if sqlite3OsLock() returns
+** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
+** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE
+** lock. It does *not* invoke the busy handler when upgrading from
+** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
+** (which occurs during hot-journal rollback). Summary:
+**
+** Transition | Invokes xBusyHandler
+** --------------------------------------------------------
+** NO_LOCK -> SHARED_LOCK | Yes
+** SHARED_LOCK -> RESERVED_LOCK | No
+** SHARED_LOCK -> EXCLUSIVE_LOCK | No
+** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes
+**
+** If the busy-handler callback returns non-zero, the lock is
+** retried. If it returns zero, then the SQLITE_BUSY error is
+** returned to the caller of the pager API function.
*/
void sqlite3PagerSetBusyhandler(
- Pager *pPager,
- int (*xBusyHandler)(void *),
- void *pBusyHandlerArg
+ Pager *pPager, /* Pager object */
+ int (*xBusyHandler)(void *), /* Pointer to busy-handler function */
+ void *pBusyHandlerArg /* Argument to pass to xBusyHandler */
){
pPager->xBusyHandler = xBusyHandler;
pPager->pBusyHandlerArg = pBusyHandlerArg;
}
/*
-** Set the reinitializer for this pager. If not NULL, the reinitializer
-** is called when the content of a page in cache is 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.
+** Set the reinitializer for this pager. If not NULL, the reinitializer
+** is called when the content of a page in cache is modified (restored)
+** as part of a transaction or savepoint rollback. The callback gives
+** higher-level code an opportunity to restore the EXTRA section to
+** agree with the restored page data.
*/
void sqlite3PagerSetReiniter(Pager *pPager, void (*xReinit)(DbPage*)){
pPager->xReiniter = xReinit;
}
/*
-** Set the page size to *pPageSize. If the suggest new page size is
-** inappropriate, then an alternative page size is set to that
-** value before returning.
+** Change the page size used by the Pager object. The new page size
+** is passed in *pPageSize.
+**
+** If the pager is in the error state when this function is called, it
+** is a no-op. The value returned is the error state error code (i.e.
+** one of SQLITE_IOERR, SQLITE_CORRUPT or SQLITE_FULL).
+**
+** Otherwise, if all of the following are true:
+**
+** * the new page size (value of *pPageSize) is valid (a power
+** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
+**
+** * there are no outstanding page references, and
+**
+** * the database is either not an in-memory database or it is
+** an in-memory database that currently consists of zero pages.
+**
+** then the pager object page size is set to *pPageSize.
+**
+** If the page size is changed, then this function uses sqlite3PagerMalloc()
+** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt
+** fails, SQLITE_NOMEM is returned and the page size remains unchanged.
+** In all other cases, SQLITE_OK is returned.
+**
+** If the page size is not changed, either because one of the enumerated
+** conditions above is not true, the pager was in error state when this
+** function was called, or because the memory allocation attempt failed,
+** then *pPageSize is set to the old, retained page size before returning.
*/
int sqlite3PagerSetPagesize(Pager *pPager, u16 *pPageSize){
int rc = pPager->errCode;
}else{
pager_reset(pPager);
pPager->pageSize = pageSize;
- if( !pPager->memDb ) setSectorSize(pPager);
sqlite3PageFree(pPager->pTmpSpace);
pPager->pTmpSpace = pNew;
sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
** Read the first N bytes from the beginning of the file into memory
** that pDest points to.
**
-** No error checking is done. The rational for this is that this function
-** may be called even if the file does not exist or contain a header. In
-** these cases sqlite3OsRead() will return an error, to which the correct
-** response is to zero the memory at pDest and continue. A real IO error
-** will presumably recur and be picked up later (Todo: Think about this).
+** If the pager was opened on a transient file (zFilename==""), or
+** opened on a file less than N bytes in size, the output buffer is
+** zeroed and SQLITE_OK returned. The rationale for this is that this
+** function is used to read database headers, and a new transient or
+** zero sized database has a header than consists entirely of zeroes.
+**
+** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
+** the error code is returned to the caller and the contents of the
+** output buffer undefined.
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
int rc = SQLITE_OK;
memset(pDest, 0, N);
- assert(pPager->fd->pMethods||pPager->tempFile);
- if( pPager->fd->pMethods ){
+ assert( isOpen(pPager->fd) || pPager->tempFile );
+ if( isOpen(pPager->fd) ){
IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
if( rc==SQLITE_IOERR_SHORT_READ ){
}
/*
-** Return the total number of pages in the disk file associated with
-** pPager.
+** Return the total number of pages in the database file associated
+** with pPager. Normally, this is calculated as (<db file size>/<page-size>).
+** However, if the file is between 1 and <page-size> bytes in size, then
+** this is considered a 1 page file.
**
-** If the PENDING_BYTE lies on the page directly after the end of the
-** file, then consider this page part of the file too. For example, if
-** PENDING_BYTE is byte 4096 (the first byte of page 5) and the size of the
-** file is 4096 bytes, 5 is returned instead of 4.
+** If the pager is in error state when this function is called, then the
+** error state error code is returned and *pnPage left unchanged. Or,
+** if the file system has to be queried for the size of the file and
+** the query attempt returns an IO error, the IO error code is returned
+** and *pnPage is left unchanged.
+**
+** Otherwise, if everything is successful, then SQLITE_OK is returned
+** and *pnPage is set to the number of pages in the database.
*/
int sqlite3PagerPagecount(Pager *pPager, int *pnPage){
- i64 n = 0;
- int rc;
- assert( pPager!=0 );
+ Pgno nPage; /* Value to return via *pnPage */
+
+ /* If the pager is already in the error state, return the error code. */
if( pPager->errCode ){
- rc = pPager->errCode;
- return rc;
+ return pPager->errCode;
}
+
+ /* Determine the number of pages in the file. Store this in nPage. */
if( pPager->dbSizeValid ){
- n = pPager->dbSize;
- } else {
- assert(pPager->fd->pMethods||pPager->tempFile);
- if( (pPager->fd->pMethods)
- && (rc = sqlite3OsFileSize(pPager->fd, &n))!=SQLITE_OK ){
+ nPage = pPager->dbSize;
+ }else{
+ int rc; /* Error returned by OsFileSize() */
+ i64 n = 0; /* File size in bytes returned by OsFileSize() */
+
+ assert( isOpen(pPager->fd) || pPager->tempFile );
+ if( isOpen(pPager->fd) && (rc = sqlite3OsFileSize(pPager->fd, &n)) ){
pager_error(pPager, rc);
return rc;
}
if( n>0 && n<pPager->pageSize ){
- n = 1;
+ nPage = 1;
}else{
- n /= pPager->pageSize;
+ nPage = n / pPager->pageSize;
}
if( pPager->state!=PAGER_UNLOCK ){
- pPager->dbSize = (Pgno)n;
- pPager->dbFileSize = (Pgno)n;
+ pPager->dbSize = (Pgno)nPage;
+ pPager->dbFileSize = (Pgno)nPage;
pPager->dbSizeValid = 1;
}
}
- if( n==(PENDING_BYTE/pPager->pageSize) ){
- n++;
- }
- if( n>pPager->mxPgno ){
- pPager->mxPgno = (Pgno)n;
+
+ /* If the current number of pages in the file is greater than the
+ ** configured maximum pager number, increase the allowed limit so
+ ** that the file can be read.
+ */
+ if( nPage>pPager->mxPgno ){
+ pPager->mxPgno = (Pgno)nPage;
}
+
+ /* Set the output variable and return SQLITE_OK */
if( pnPage ){
- *pnPage = (int)n;
+ *pnPage = nPage;
}
return SQLITE_OK;
}
/*
-** Forward declaration
+** Forward declaration.
*/
static int syncJournal(Pager*);
/*
-** Try to obtain a lock on a file. Invoke the busy callback if the lock
-** is currently not available. Repeat until the busy callback returns
-** false or until the lock succeeds.
+** Try to obtain a lock of type locktype on the database file. If
+** a similar or greater lock is already held, this function is a no-op
+** (returning SQLITE_OK immediately).
+**
+** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke
+** the busy callback if the lock is currently not available. Repeat
+** until the busy callback returns false or until the attempt to
+** obtain the lock succeeds.
**
** Return SQLITE_OK on success and an error code if we cannot obtain
-** the lock.
+** the lock. If the lock is obtained successfully, set the Pager.state
+** variable to locktype before returning.
*/
static int pager_wait_on_lock(Pager *pPager, int locktype){
- int rc;
+ int rc; /* Return code */
/* The OS lock values must be the same as the Pager lock values */
assert( PAGER_SHARED==SHARED_LOCK );
/* If the file is currently unlocked then the size must be unknown */
assert( pPager->state>=PAGER_SHARED || pPager->dbSizeValid==0 );
+ /* Check that this is either a no-op (because the requested lock is
+ ** already held, or one of the transistions that the busy-handler
+ ** may be invoked during, according to the comment above
+ ** sqlite3PagerSetBusyhandler().
+ */
+ assert( (pPager->state>=locktype)
+ || (pPager->state==PAGER_UNLOCK && locktype==PAGER_SHARED)
+ || (pPager->state==PAGER_RESERVED && locktype==PAGER_EXCLUSIVE)
+ );
+
if( pPager->state>=locktype ){
rc = SQLITE_OK;
}else{
void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
assert( pPager->dbSizeValid );
assert( pPager->dbSize>=nPage );
+ assert( pPager->state>=PAGER_RESERVED );
pPager->dbSize = nPage;
}
-
-/*
-** Return the current size of the database file image in pages. This
-** function differs from sqlite3PagerPagecount() in two ways:
-**
-** a) It may only be called when at least one reference to a database
-** page is held. This guarantees that the database size is already
-** known and a call to sqlite3OsFileSize() is not required.
-**
-** b) The return value is not adjusted for the locking page.
-*/
-Pgno sqlite3PagerImageSize(Pager *pPager){
- assert( pPager->dbSizeValid );
- return pPager->dbSize;
-}
#endif /* ifndef SQLITE_OMIT_AUTOVACUUM */
/*
** to the caller.
*/
int sqlite3PagerClose(Pager *pPager){
-
disable_simulated_io_errors();
sqlite3BeginBenignMalloc();
pPager->errCode = 0;
pPager->exclusiveMode = 0;
pager_reset(pPager);
- if( !MEMDB ){
+ if( MEMDB ){
+ pager_unlock(pPager);
+ }else{
/* Set Pager.journalHdr to -1 for the benefit of the pager_playback()
** call which may be made from within pagerUnlockAndRollback(). If it
** is not -1, then the unsynced portion of an open journal file may
pPager->journalHdr = -1;
pagerUnlockAndRollback(pPager);
}
- enable_simulated_io_errors();
sqlite3EndBenignMalloc();
+ enable_simulated_io_errors();
PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
IOTRACE(("CLOSE %p\n", pPager))
- if( pPager->journalOpen ){
- sqlite3OsClose(pPager->jfd);
- }
- sqlite3BitvecDestroy(pPager->pInJournal);
- sqlite3BitvecDestroy(pPager->pAlwaysRollback);
- releaseAllSavepoint(pPager);
sqlite3OsClose(pPager->fd);
- /* Temp files are automatically deleted by the OS
- ** if( pPager->tempFile ){
- ** sqlite3OsDelete(pPager->zFilename);
- ** }
- */
-
sqlite3PageFree(pPager->pTmpSpace);
sqlite3PcacheClose(pPager->pPCache);
+
+ assert( !pPager->aSavepoint && !pPager->pInJournal );
+ assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
+
sqlite3_free(pPager);
return SQLITE_OK;
}
#if !defined(NDEBUG) || defined(SQLITE_TEST)
/*
-** Return the page number for the given page data.
+** Return the page number for page pPg.
*/
-Pgno sqlite3PagerPagenumber(DbPage *p){
- return p->pgno;
+Pgno sqlite3PagerPagenumber(DbPage *pPg){
+ return pPg->pgno;
}
#endif
/*
-** Increment the reference count for a page. The input pointer is
-** a reference to the page data.
+** Increment the reference count for page pPg.
*/
-int sqlite3PagerRef(DbPage *pPg){
+void sqlite3PagerRef(DbPage *pPg){
sqlite3PcacheRef(pPg);
- return SQLITE_OK;
}
/*
-** Sync the journal. In other words, make sure all the pages that have
+** 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.
+** disk and can be restored in the event of a hot-journal rollback.
+**
+** If the Pager.needSync flag is not set, then this function is a
+** no-op. Otherwise, the actions required depend on the journal-mode
+** and the device characteristics of the the file-system, as follows:
+**
+** * If the journal file is an in-memory journal file, no action need
+** be taken.
+**
+** * Otherwise, if the device does not support the SAFE_APPEND property,
+** then the nRec field of the most recently written journal header
+** is updated to contain the number of journal records that have
+** been written following it. If the pager is operating in full-sync
+** mode, then the journal file is synced before this field is updated.
**
-** For temporary databases, we do not care if we are able to rollback
-** after a power failure, so no sync occurs.
+** * If the device does not support the SEQUENTIAL property, then
+** journal file is synced.
**
-** If the IOCAP_SEQUENTIAL flag is set for the persistent media on which
-** the database is stored, then OsSync() is never called on the journal
-** file. In this case all that is required is to update the nRec field in
-** the journal header.
+** Or, in pseudo-code:
**
-** This routine clears the needSync field of every page current held in
-** memory.
+** if( NOT <in-memory journal> ){
+** if( NOT SAFE_APPEND ){
+** if( <full-sync mode> ) xSync(<journal file>);
+** <update nRec field>
+** }
+** if( NOT SEQUENTIAL ) xSync(<journal file>);
+** }
+**
+** The Pager.needSync flag is never be set for temporary files, or any
+** file operating in no-sync mode (Pager.noSync set to non-zero).
+**
+** If successful, this routine clears the PGHDR_NEED_SYNC flag of every
+** page currently held in memory before returning SQLITE_OK. If an IO
+** error is encountered, then the IO error code is returned to the caller.
*/
static int syncJournal(Pager *pPager){
- int rc = SQLITE_OK;
-
- /* Sync the journal before modifying the main database
- ** (assuming there is a journal and it needs to be synced.)
- */
if( pPager->needSync ){
assert( !pPager->tempFile );
if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
- int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
- assert( pPager->journalOpen );
+ int rc; /* Return code */
+ const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+ assert( isOpen(pPager->jfd) );
if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
- i64 jrnlOff = journalHdrOffset(pPager);
- u8 zMagic[8];
+ /* Variable iNRecOffset is set to the offset in the journal file
+ ** of the nRec field of the most recently written journal header.
+ ** This field will be updated following the xSync() operation
+ ** on the journal file. */
+ i64 iNRecOffset = pPager->journalHdr + sizeof(aJournalMagic);
/* This block deals with an obscure problem. If the last connection
** that wrote to this database was operating in persistent-journal
** To work around this, if the journal file does appear to contain
** a valid header following Pager.journalOff, then write a 0x00
** byte to the start of it to prevent it from being recognized.
+ **
+ ** Variable iNextHdrOffset is set to the offset at which this
+ ** problematic header will occur, if it exists. aMagic is used
+ ** as a temporary buffer to inspect the first couple of bytes of
+ ** the potential journal header.
*/
- rc = sqlite3OsRead(pPager->jfd, zMagic, 8, jrnlOff);
- if( rc==SQLITE_OK && 0==memcmp(zMagic, aJournalMagic, 8) ){
+ i64 iNextHdrOffset = journalHdrOffset(pPager);
+ u8 aMagic[8];
+ rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
+ if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
static const u8 zerobyte = 0;
- rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, jrnlOff);
+ rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
}
if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
return rc;
PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags);
- if( rc!=0 ) return rc;
+ if( rc!=SQLITE_OK ) return rc;
}
-
- jrnlOff = pPager->journalHdr + sizeof(aJournalMagic);
- IOTRACE(("JHDR %p %lld %d\n", pPager, jrnlOff, 4));
- rc = write32bits(pPager->jfd, jrnlOff, pPager->nRec);
- if( rc ) return rc;
+ IOTRACE(("JHDR %p %lld %d\n", pPager, iNRecOffset, 4));
+ rc = write32bits(pPager->jfd, iNRecOffset, pPager->nRec);
+ if( rc!=SQLITE_OK ) return rc;
}
if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags|
(pPager->sync_flags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
);
- if( rc!=0 ) return rc;
+ if( rc!=SQLITE_OK ) return rc;
}
- pPager->journalStarted = 1;
}
- pPager->needSync = 0;
- /* Erase the needSync flag from every page.
+ /* The journal file was just successfully synced. Set Pager.needSync
+ ** to zero and clear the PGHDR_NEED_SYNC flag on all pagess.
*/
+ pPager->needSync = 0;
+ pPager->journalStarted = 1;
sqlite3PcacheClearSyncFlags(pPager->pPCache);
}
- return rc;
+ return SQLITE_OK;
}
/*
-** Given a list of pages (connected by the PgHdr.pDirty pointer) write
-** every one of those pages out to the database file. No calls are made
-** to the page-cache to mark the pages as clean. It is the responsibility
-** of the caller to use PcacheCleanAll() or PcacheMakeClean() to mark
-** the pages as clean.
+** The argument is the first in a linked list of dirty pages connected
+** by the PgHdr.pDirty pointer. This function writes each one of the
+** in-memory pages in the list to the database file. The argument may
+** be NULL, representing an empty list. In this case this function is
+** a no-op.
+**
+** The pager must hold at least a RESERVED lock when this function
+** is called. Before writing anything to the database file, this lock
+** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
+** SQLITE_BUSY is returned and no data is written to the database file.
+**
+** If the pager is a temp-file pager and the actual file-system file
+** is not yet open, it is created and opened before any data is
+** written out.
+**
+** Once the lock has been upgraded and, if necessary, the file opened,
+** the pages are written out to the database file in list order. Writing
+** a page is skipped if it meets either of the following criteria:
+**
+** * The page number is greater than Pager.dbSize, or
+** * The PGHDR_DONT_WRITE flag is set on the page.
+**
+** If writing out a page causes the database file to grow, Pager.dbFileSize
+** is updated accordingly. If page 1 is written out, then the value cached
+** in Pager.dbFileVers[] is updated to match the new value stored in
+** the database file.
+**
+** If everything is successful, SQLITE_OK is returned. If an IO error
+** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
+** be obtained, SQLITE_BUSY is returned.
*/
static int pager_write_pagelist(PgHdr *pList){
- Pager *pPager;
- int rc;
+ Pager *pPager; /* Pager object */
+ int rc; /* Return code */
if( pList==0 ) return SQLITE_OK;
pPager = pList->pPager;
/* At this point there may be either a RESERVED or EXCLUSIVE lock on the
** database file. If there is already an EXCLUSIVE lock, the following
- ** calls to sqlite3OsLock() are no-ops.
+ ** call is a no-op.
**
** Moving the lock from RESERVED to EXCLUSIVE actually involves going
** through an intermediate state PENDING. A PENDING lock prevents new
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
+ assert( pPager->state>=PAGER_RESERVED );
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
- if( rc!=SQLITE_OK ){
- return rc;
- }
- while( pList ){
+ /* If the file is a temp-file has not yet been opened, open it now. It
+ ** is not possible for rc to be other than SQLITE_OK if this branch
+ ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
+ */
+ if( !isOpen(pPager->fd) ){
+ assert( pPager->tempFile && rc==SQLITE_OK );
+ rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
+ }
- /* If the file has not yet been opened, open it now. */
- if( !pPager->fd->pMethods ){
- assert(pPager->tempFile);
- rc = sqlite3PagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
- if( rc ) return rc;
- }
+ while( rc==SQLITE_OK && pList ){
+ Pgno pgno = pList->pgno;
/* If there are dirty pages in the page cache with page numbers greater
** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
** make the file smaller (presumably by auto-vacuum code). Do not write
** any such pages to the file.
+ **
+ ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
+ ** set (set by sqlite3PagerDontWrite()).
*/
- if( pList->pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
- i64 offset = (pList->pgno-1)*(i64)pPager->pageSize;
- char *pData = CODEC2(pPager, pList->pData, pList->pgno, 6);
+ if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
+ i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */
+ char *pData = CODEC2(pPager, pList->pData, pgno, 6); /* Data to write */
- PAGERTRACE(("STORE %d page %d hash(%08x)\n",
- PAGERID(pPager), pList->pgno, pager_pagehash(pList)));
- IOTRACE(("PGOUT %p %d\n", pPager, pList->pgno));
+ /* Write out the page data. */
rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
- PAGER_INCR(sqlite3_pager_writedb_count);
- PAGER_INCR(pPager->nWrite);
- if( pList->pgno==1 ){
+
+ /* If page 1 was just written, update Pager.dbFileVers to match
+ ** the value now stored in the database file. If writing this
+ ** page caused the database file to grow, update dbFileSize.
+ */
+ if( pgno==1 ){
memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
}
- if( pList->pgno>pPager->dbFileSize ){
- pPager->dbFileSize = pList->pgno;
+ if( pgno>pPager->dbFileSize ){
+ pPager->dbFileSize = pgno;
}
+
+ PAGERTRACE(("STORE %d page %d hash(%08x)\n",
+ PAGERID(pPager), pgno, pager_pagehash(pList)));
+ IOTRACE(("PGOUT %p %d\n", pPager, pgno));
+ PAGER_INCR(sqlite3_pager_writedb_count);
+ PAGER_INCR(pPager->nWrite);
+ }else{
+ PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
}
-#ifndef NDEBUG
- else{
- PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pList->pgno));
- }
-#endif
- if( rc ) return rc;
#ifdef SQLITE_CHECK_PAGES
pList->pageHash = pager_pagehash(pList);
#endif
pList = pList->pDirty;
}
- return SQLITE_OK;
+ return rc;
}
/*
-** Add the page to the sub-journal. It is the callers responsibility to
-** use subjRequiresPage() to check that it is really required before
-** calling this function.
+** Append a record of the current state of page pPg to the sub-journal.
+** It is the callers responsibility to use subjRequiresPage() to check
+** that it is really required before calling this function.
+**
+** If successful, set the bit corresponding to pPg->pgno in the bitvecs
+** for all open savepoints before returning.
+**
+** This function returns SQLITE_OK if everything is successful, an IO
+** error code if the attempt to write to the sub-journal fails, or
+** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
+** bitvec.
*/
static int subjournalPage(PgHdr *pPg){
int rc;
void *pData = pPg->pData;
Pager *pPager = pPg->pPager;
- i64 offset = pPager->stmtNRec*(4+pPager->pageSize);
+ i64 offset = pPager->nSubRec*(4+pPager->pageSize);
char *pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
}
if( rc==SQLITE_OK ){
- pPager->stmtNRec++;
+ pPager->nSubRec++;
assert( pPager->nSavepoint>0 );
rc = addToSavepointBitvecs(pPager, pPg->pgno);
+ testcase( rc!=SQLITE_OK );
}
return rc;
}
/*
** This function is called by the pcache layer when it has reached some
-** soft memory limit. The argument is a pointer to a purgeable Pager
-** object. This function attempts to make a single dirty page that has no
-** outstanding references (if one exists) clean so that it can be recycled
-** by the pcache layer.
+** soft memory limit. The first argument is a pointer to a Pager object
+** (cast as a void*). The pager is always 'purgeable' (not an in-memory
+** database). The second argument is a reference to a page that is
+** currently dirty but has no outstanding references. The page
+** is always associated with the Pager object passed as the first
+** argument.
+**
+** The job of this function is to make pPg clean by writing its contents
+** out to the database file, if possible. This may involve syncing the
+** journal file.
+**
+** If successful, sqlite3PcacheMakeClean() is called on the page and
+** SQLITE_OK returned. If an IO error occurs while trying to make the
+** page clean, the IO error code is returned. If the page cannot be
+** made clean for some other reason, but no error occurs, then SQLITE_OK
+** is returned by sqlite3PcacheMakeClean() is not called.
*/
static int pagerStress(void *p, PgHdr *pPg){
Pager *pPager = (Pager *)p;
int rc = SQLITE_OK;
- if( pPager->doNotSync ){
+ assert( pPg->pPager==pPager );
+ assert( pPg->flags&PGHDR_DIRTY );
+
+ /* The doNotSync flag is set by the sqlite3PagerWrite() function while it
+ ** is journalling a set of two or more database pages that are stored
+ ** on the same disk sector. Syncing the journal is not allowed while
+ ** this is happening as it is important that all members of such a
+ ** set of pages are synced to disk together. So, if the page this function
+ ** is trying to make clean will require a journal sync and the doNotSync
+ ** flag is set, return without doing anything. The pcache layer will
+ ** just have to go ahead and allocate a new page buffer instead of
+ ** reusing pPg.
+ **
+ ** Similarly, if the pager has already entered the error state, do not
+ ** try to write the contents of pPg to disk.
+ */
+ if( pPager->errCode || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC) ){
return SQLITE_OK;
}
- assert( pPg->flags&PGHDR_DIRTY );
- if( pPager->errCode==SQLITE_OK ){
- if( pPg->flags&PGHDR_NEED_SYNC ){
- rc = syncJournal(pPager);
- if( rc==SQLITE_OK && pPager->fullSync &&
- !(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
- !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
- ){
- pPager->nRec = 0;
- rc = writeJournalHdr(pPager);
- }
- }
- if( rc==SQLITE_OK ){
- pPg->pDirty = 0;
- if( pPg->pgno>pPager->dbSize && subjRequiresPage(pPg) ){
- rc = subjournalPage(pPg);
- }
- if( rc==SQLITE_OK ){
- rc = pager_write_pagelist(pPg);
- }
- }
- if( rc!=SQLITE_OK ){
- pager_error(pPager, rc);
+ /* Sync the journal file if required. */
+ if( pPg->flags&PGHDR_NEED_SYNC ){
+ rc = syncJournal(pPager);
+ if( rc==SQLITE_OK && pPager->fullSync &&
+ !(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
+ !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
+ ){
+ pPager->nRec = 0;
+ rc = writeJournalHdr(pPager);
}
}
+ /* If the page number of this page is larger than the current size of
+ ** the database image, it may need to be written to the sub-journal.
+ ** This is because the call to pager_write_pagelist() below will not
+ ** actually write data to the file in this case.
+ **
+ ** Consider the following sequence of events:
+ **
+ ** BEGIN;
+ ** <journal page X>
+ ** <modify page X>
+ ** SAVEPOINT sp;
+ ** <shrink database file to Y pages>
+ ** pagerStress(page X)
+ ** ROLLBACK TO sp;
+ **
+ ** If (X>Y), then when pagerStress is called page X will not be written
+ ** out to the database file, but will be dropped from the cache. Then,
+ ** following the "ROLLBACK TO sp" statement, reading page X will read
+ ** data from the database file. This will be the copy of page X as it
+ ** was when the transaction started, not as it was when "SAVEPOINT sp"
+ ** was executed.
+ **
+ ** The solution is to write the current data for page X into the
+ ** sub-journal file now (if it is not already there), so that it will
+ ** be restored to its current value when the "ROLLBACK TO sp" is
+ ** executed.
+ */
+ if( rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg) ){
+ rc = subjournalPage(pPg);
+ }
+
+ /* Write the contents of the page out to the database file. */
+ if( rc==SQLITE_OK ){
+ pPg->pDirty = 0;
+ rc = pager_write_pagelist(pPg);
+ }
+
+ /* Mark the page as clean. */
if( rc==SQLITE_OK ){
PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
sqlite3PcacheMakeClean(pPg);
}
- return rc;
+
+ return pager_error(pPager, rc);
}
/*
-** Return 1 if there is a hot journal on the given pager.
-** A hot journal is one that needs to be played back.
+** This function is called after transitioning from PAGER_UNLOCK to
+** PAGER_SHARED state. It tests if there is a hot journal present in
+** the file-system for the given pager. A hot journal is one that
+** needs to be played back. According to this function, a hot-journal
+** file exists if the following three criteria are met:
+**
+** * The journal file exists in the file system, and
+** * No process holds a RESERVED or greater lock on the database file, and
+** * The database file itself is greater than 0 bytes in size.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
-** database with the same name. Just delete the journal.
-**
-** Return negative if unable to determine the status of the journal.
+** database with the same name. In this case the journal file is
+** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
+** is returned.
**
** This routine does not open the journal file to examine its
** content. Hence, the journal might contain the name of a master
** journal file exists and is not empty this routine assumes it
** is hot. The pager_playback() routine will discover that the
** journal file is not really hot and will no-op.
+**
+** If a hot-journal file is found to exist, *pExists is set to 1 and
+** SQLITE_OK returned. If no hot-journal file is present, *pExists is
+** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
+** to determine whether or not a hot-journal file exists, the IO error
+** code is returned and the value of *pExists is undefined.
*/
static int hasHotJournal(Pager *pPager, int *pExists){
- sqlite3_vfs *pVfs = pPager->pVfs;
- int rc = SQLITE_OK;
- int exists = 0;
- int locked = 0;
+ sqlite3_vfs * const pVfs = pPager->pVfs;
+ int rc; /* Return code */
+ int exists = 0; /* True if a journal file is present */
+ int locked = 0; /* True if some process holds a RESERVED lock */
+
assert( pPager!=0 );
assert( pPager->useJournal );
- assert( pPager->fd->pMethods );
+ assert( isOpen(pPager->fd) );
+
*pExists = 0;
rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
if( rc==SQLITE_OK && exists ){
rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
- }
- if( rc==SQLITE_OK && exists && !locked ){
- int nPage;
- rc = sqlite3PagerPagecount(pPager, &nPage);
- if( rc==SQLITE_OK ){
- if( nPage==0 ){
- sqlite3OsDelete(pVfs, pPager->zJournal, 0);
- }else{
- *pExists = 1;
+ if( rc==SQLITE_OK && !locked ){
+ int nPage;
+ rc = sqlite3PagerPagecount(pPager, &nPage);
+ if( rc==SQLITE_OK ){
+ if( nPage==0 ){
+ sqlite3OsDelete(pVfs, pPager->zJournal, 0);
+ }else{
+ *pExists = 1;
+ }
}
}
}
}
/*
-** Read the content of page pPg out of the database file.
+** Read the content for page pPg out of the database file and into
+** pPg->pData. A shared lock or greater must be held on the database
+** file before this function is called.
+**
+** If page 1 is read, then the value of Pager.dbFileVers[] is set to
+** the value read from the database file.
+**
+** If an IO error occurs, then the IO error is returned to the caller.
+** Otherwise, SQLITE_OK is returned.
*/
-static int readDbPage(Pager *pPager, PgHdr *pPg, Pgno pgno){
- int rc;
- i64 offset;
- assert( MEMDB==0 );
- assert(pPager->fd->pMethods||pPager->tempFile);
- if( !pPager->fd->pMethods ){
+static int readDbPage(PgHdr *pPg){
+ Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
+ Pgno pgno = pPg->pgno; /* Page number to read */
+ int rc; /* Return code */
+ i64 iOffset; /* Byte offset of file to read from */
+
+ assert( pPager->state>=PAGER_SHARED && !MEMDB );
+
+ if( !isOpen(pPager->fd) ){
+ assert( pPager->tempFile );
return SQLITE_IOERR_SHORT_READ;
}
- offset = (pgno-1)*(i64)pPager->pageSize;
- rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, offset);
+ iOffset = (pgno-1)*(i64)pPager->pageSize;
+ rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
+ if( pgno==1 ){
+ u8 *dbFileVers = &((u8*)pPg->pData)[24];
+ memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
+ }
+ CODEC1(pPager, pPg->pData, pgno, 3);
+
PAGER_INCR(sqlite3_pager_readdb_count);
PAGER_INCR(pPager->nRead);
IOTRACE(("PGIN %p %d\n", pPager, pgno));
- if( pgno==1 ){
- memcpy(&pPager->dbFileVers, &((u8*)pPg->pData)[24],
- sizeof(pPager->dbFileVers));
- }
- CODEC1(pPager, pPg->pData, pPg->pgno, 3);
PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
- PAGERID(pPager), pPg->pgno, pager_pagehash(pPg)));
+ PAGERID(pPager), pgno, pager_pagehash(pPg)));
+
return rc;
}
-
/*
** This function is called to obtain the shared lock required before
** data may be read from the pager cache. If the shared lock has already
** is performed immediately.
*/
static int pagerSharedLock(Pager *pPager){
- int rc = SQLITE_OK;
- int isErrorReset = 0;
+ int rc = SQLITE_OK; /* Return code */
+ int isErrorReset = 0; /* True if recovering from error state */
/* If this database is opened for exclusive access, has no outstanding
- ** page references and is in an error-state, now is the chance to clear
+ ** page references and is in an error-state, this is a chance to clear
** the error. Discard the contents of the pager-cache and treat any
** open journal file as a hot-journal.
*/
if( !MEMDB && pPager->exclusiveMode
&& sqlite3PcacheRefCount(pPager->pPCache)==0 && pPager->errCode
){
- if( pPager->journalOpen ){
+ if( isOpen(pPager->jfd) ){
isErrorReset = 1;
}
pPager->errCode = SQLITE_OK;
}
if( pPager->state==PAGER_UNLOCK || isErrorReset ){
- sqlite3_vfs *pVfs = pPager->pVfs;
+ sqlite3_vfs * const pVfs = pPager->pVfs;
int isHotJournal = 0;
assert( !MEMDB );
assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
** 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.
+ ** database is safe to read while this process is still rolling the
+ ** hot-journal back.
**
- ** Because the intermediate RESERVED lock is not requested, the
- ** second process will get to this point in the code and fail to
- ** obtain its own EXCLUSIVE lock on the database file.
+ ** Because the intermediate RESERVED lock is not requested, any
+ ** other process attempting to access the database file will get to
+ ** this point in the code and fail to obtain its own EXCLUSIVE lock
+ ** on the database file.
*/
if( pPager->state<EXCLUSIVE_LOCK ){
rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
** OsTruncate() call used in exclusive-access mode also requires
** a read/write file handle.
*/
- if( !isErrorReset && pPager->journalOpen==0 ){
+ if( !isOpen(pPager->jfd) ){
int res;
rc = sqlite3OsAccess(pVfs,pPager->zJournal,SQLITE_ACCESS_EXISTS,&res);
if( rc==SQLITE_OK ){
int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
assert( !pPager->tempFile );
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
- assert( rc!=SQLITE_OK || pPager->jfd->pMethods );
+ assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
rc = SQLITE_CANTOPEN;
sqlite3OsClose(pPager->jfd);
if( rc!=SQLITE_OK ){
goto failed;
}
- pPager->journalOpen = 1;
+
+ /* TODO: Why are these cleared here? Is it necessary? */
pPager->journalStarted = 0;
pPager->journalOff = 0;
pPager->setMaster = 0;
rc = pager_error(pPager, rc);
goto failed;
}
- assert(pPager->state==PAGER_SHARED ||
- (pPager->exclusiveMode && pPager->state>PAGER_SHARED)
+ assert( (pPager->state==PAGER_SHARED)
+ || (pPager->exclusiveMode && pPager->state>PAGER_SHARED)
);
}
return rc;
}
-/*
-** Make sure we have the content for a page. If the page was
-** previously acquired with noContent==1, then the content was
-** just initialized to zeros instead of being read from disk.
-** But now we need the real data off of disk. So make sure we
-** have it. Read it in if we do not have it already.
-*/
-static int pager_get_content(PgHdr *pPg){
- if( pPg->flags&PGHDR_NEED_READ ){
- int rc = readDbPage(pPg->pPager, pPg, pPg->pgno);
- if( rc==SQLITE_OK ){
- pPg->flags &= ~PGHDR_NEED_READ;
- }else{
- return rc;
- }
- }
- return SQLITE_OK;
-}
-
/*
** If the reference count has reached zero, and the pager is not in the
** middle of a write transaction or opened in exclusive mode, unlock it.
**
** If noContent is false, the page contents are actually read from disk.
** If noContent is true, it means that we do not care about the contents
-** of the page at this time, so do not do a disk read. Just fill in the
-** page content with zeros. But mark the fact that we have not read the
-** content by setting the PgHdr.needRead flag. Later on, if
-** sqlite3PagerWrite() is called on this page or if this routine is
-** called again with noContent==0, that means that the content is needed
-** and the disk read should occur at that point.
+** of the page. This occurs in two seperate scenarios:
+**
+** a) When reading a free-list leaf page from the database, and
+**
+** b) When a savepoint is being rolled back and we need to load
+** a new page into the cache to populate with the data read
+** from the savepoint journal.
+**
+** If noContent is true, then the data returned is zeroed instead of
+** being read from the database. Additionally, the bits corresponding
+** to pgno in Pager.pInJournal (bitvec of pages already written to the
+** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
+** savepoints are set. This means if the page is made writable at any
+** point in the future, using a call to sqlite3PagerWrite(), its contents
+** will not be journaled. This saves IO.
*/
int sqlite3PagerAcquire(
Pager *pPager, /* The pager open on the database file */
}
memset(pPg->pData, 0, pPager->pageSize);
if( noContent ){
- pPg->flags |= PGHDR_NEED_READ;
+ /* Failure to set the bits in the InJournal bit-vectors is benign.
+ ** It merely means that we might do some extra work to journal a
+ ** page that does not need to be journaled. Nevertheless, be sure
+ ** to test the case where a malloc error occurs while trying to set
+ ** a bit in a bit vector.
+ */
+ sqlite3BeginBenignMalloc();
+ TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
+ testcase( rc==SQLITE_NOMEM );
+ TESTONLY( rc = ) addToSavepointBitvecs(pPager, pPg->pgno);
+ testcase( rc==SQLITE_NOMEM );
+ sqlite3EndBenignMalloc();
}
IOTRACE(("ZERO %p %d\n", pPager, pgno));
}else{
- rc = readDbPage(pPager, pPg, pgno);
+ assert( pPg->pPager==pPager && pPg->pgno==pgno );
+ rc = readDbPage(pPg);
if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
- /* sqlite3PagerUnref(pPg); */
pagerDropPage(pPg);
return rc;
}
#endif
}else{
/* The requested page is in the page cache. */
- assert(sqlite3PcacheRefCount(pPager->pPCache)>0 || pgno==1);
PAGER_INCR(pPager->nHit);
- if( !noContent ){
- rc = pager_get_content(pPg);
- if( rc ){
- sqlite3PagerUnref(pPg);
- return rc;
- }
- }
}
*ppPage = pPg;
** are released, a rollback occurs and the lock on the database is
** removed.
*/
-int sqlite3PagerUnref(DbPage *pPg){
+void sqlite3PagerUnref(DbPage *pPg){
if( pPg ){
Pager *pPager = pPg->pPager;
sqlite3PcacheRelease(pPg);
pagerUnlockIfUnused(pPager);
}
- return SQLITE_OK;
}
/*
*/
static int openSubJournal(Pager *pPager){
int rc = SQLITE_OK;
- if( pPager->journalOpen && !pPager->sjfd->pMethods ){
+ if( isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ){
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
sqlite3MemJournalOpen(pPager->sjfd);
}else{
- rc = sqlite3PagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
+ rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
}
}
return rc;
goto failed_to_open_journal;
}
- if( pPager->journalOpen==0 ){
+ if( !isOpen(pPager->jfd) ){
if( pPager->tempFile ){
flags |= (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL);
}else{
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
#endif
}
- assert( rc!=SQLITE_OK || pPager->jfd->pMethods );
+ assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
pPager->journalOff = 0;
pPager->setMaster = 0;
pPager->journalHdr = 0;
goto failed_to_open_journal;
}
}
- pPager->journalOpen = 1;
pPager->journalStarted = 0;
pPager->needSync = 0;
pPager->nRec = 0;
if( rc!=SQLITE_OK ){
return rc;
}
- pPager->dirtyCache = 0;
PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
if( pPager->useJournal && !pPager->tempFile
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
rc = pager_open_journal(pPager);
}
- }else if( pPager->journalOpen && pPager->journalOff==0 ){
+ }else if( isOpen(pPager->jfd) && pPager->journalOff==0 ){
/* This happens when the pager was in exclusive-access mode the last
** time a (read or write) transaction was successfully concluded
** by this connection. Instead of deleting the journal file it was
rc = writeJournalHdr(pPager);
}
}
- assert( !pPager->journalOpen || pPager->journalOff>0 || rc!=SQLITE_OK );
+ assert( !isOpen(pPager->jfd) || pPager->journalOff>0 || rc!=SQLITE_OK );
return rc;
}
CHECK_PAGE(pPg);
- /* If this page was previously acquired with noContent==1, that means
- ** we didn't really read in the content of the page. This can happen
- ** (for example) when the page is being moved to the freelist. But
- ** now we are (perhaps) moving the page off of the freelist for
- ** reuse and we need to know its original content so that content
- ** can be stored in the rollback journal. So do the read at this
- ** time.
- */
- rc = pager_get_content(pPg);
- if( rc ){
- return rc;
- }
-
/* Mark the page as dirty. If the page has already been written
** to the journal then we can return right away.
*/
sqlite3PcacheMakeDirty(pPg);
if( pageInJournal(pPg) && !subjRequiresPage(pPg) ){
- pPager->dirtyCache = 1;
pPager->dbModified = 1;
}else{
return rc;
}
assert( pPager->state>=PAGER_RESERVED );
- if( !pPager->journalOpen && pPager->useJournal
+ if( !isOpen(pPager->jfd) && pPager->useJournal
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
rc = pager_open_journal(pPager);
if( rc!=SQLITE_OK ) return rc;
}
- pPager->dirtyCache = 1;
pPager->dbModified = 1;
/* The transaction journal now exists and we have a RESERVED or an
** EXCLUSIVE lock on the main database file. Write the current page to
** the transaction journal if it is not there already.
*/
- if( !pageInJournal(pPg) && pPager->journalOpen ){
+ if( !pageInJournal(pPg) && isOpen(pPager->jfd) ){
if( pPg->pgno<=pPager->dbOrigSize ){
u32 cksum;
char *pData2;
** Tests show that this optimization, together with the
** sqlite3PagerDontRollback() below, more than double the speed
** of large INSERT operations and quadruple the speed of large DELETEs.
-**
-** When this routine is called, set the bit corresponding to pDbPage in
-** the Pager.pAlwaysRollback bitvec. Subsequent calls to
-** sqlite3PagerDontRollback() for the same page will thereafter be ignored.
-** This is necessary to avoid a problem where a page with data is added to
-** the freelist during one part of a transaction then removed from the
-** freelist during a later part of the same transaction and reused for some
-** other purpose. When it is first added to the freelist, this routine is
-** called. When reused, the sqlite3PagerDontRollback() routine is called.
-** But because the page contains critical data, we still need to be sure it
-** gets rolled back in spite of the sqlite3PagerDontRollback() call.
*/
-int sqlite3PagerDontWrite(DbPage *pDbPage){
- PgHdr *pPg = pDbPage;
+void sqlite3PagerDontWrite(PgHdr *pPg){
Pager *pPager = pPg->pPager;
- int rc;
-
- if( pPg->pgno>pPager->dbOrigSize ){
- return SQLITE_OK;
- }
- if( pPager->pAlwaysRollback==0 ){
- assert( pPager->pInJournal );
- pPager->pAlwaysRollback = sqlite3BitvecCreate(pPager->dbOrigSize);
- if( !pPager->pAlwaysRollback ){
- return SQLITE_NOMEM;
- }
- }
- rc = sqlite3BitvecSet(pPager->pAlwaysRollback, pPg->pgno);
-
- if( rc==SQLITE_OK && (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
- assert( pPager->state>=PAGER_SHARED );
- if( pPager->dbSize==pPg->pgno && pPager->dbOrigSize<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{
- PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
- IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
- pPg->flags |= PGHDR_DONT_WRITE;
+ if( (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
+ PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
+ IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
+ pPg->flags |= PGHDR_DONT_WRITE;
#ifdef SQLITE_CHECK_PAGES
- pPg->pageHash = pager_pagehash(pPg);
+ pPg->pageHash = pager_pagehash(pPg);
#endif
- }
}
- return rc;
-}
-
-/*
-** A call to this routine tells the pager that if a rollback occurs,
-** it is not necessary to restore the data on the given page. This
-** means that the pager does not have to record the given page in the
-** rollback journal.
-**
-** If we have not yet actually read the content of this page (if
-** the PgHdr.needRead flag is set) then this routine acts as a promise
-** that we will never need to read the page content in the future.
-** so the needRead flag can be cleared at this point.
-*/
-void sqlite3PagerDontRollback(DbPage *pPg){
- Pager *pPager = pPg->pPager;
- TESTONLY( int rc; ) /* Return value from sqlite3BitvecSet() */
-
- assert( pPager->state>=PAGER_RESERVED );
-
- /* If the journal file is not open, or DontWrite() has been called on
- ** this page (DontWrite() sets the Pager.pAlwaysRollback bit), then this
- ** function is a no-op.
- */
- if( pPager->journalOpen==0
- || sqlite3BitvecTest(pPager->pAlwaysRollback, pPg->pgno)
- || pPg->pgno>pPager->dbOrigSize
- ){
- return;
- }
-
-#ifdef SQLITE_SECURE_DELETE
- if( sqlite3BitvecTest(pPager->pInJournal, pPg->pgno)!=0
- || pPg->pgno>pPager->dbOrigSize ){
- return;
- }
-#endif
-
- /* If SECURE_DELETE is disabled, then there is no way that this
- ** routine can be called on a page for which sqlite3PagerDontWrite()
- ** has not been previously called during the same transaction.
- ** And if DontWrite() has previously been called, the following
- ** conditions must be met.
- **
- ** (Later:) Not true. If the database is corrupted by having duplicate
- ** pages on the freelist (ex: corrupt9.test) then the following is not
- ** necessarily true:
- */
- /* assert( !pPg->inJournal && (int)pPg->pgno <= pPager->dbOrigSize ); */
-
- assert( pPager->pInJournal!=0 );
- pPg->flags &= ~PGHDR_NEED_READ;
-
- /* Failure to set the bits in the InJournal bit-vectors is benign.
- ** It merely means that we might do some extra work to journal a page
- ** that does not need to be journaled. Nevertheless, be sure to test the
- ** case where a malloc error occurs while trying to set a bit in a
- ** bit vector.
- */
- sqlite3BeginBenignMalloc();
- TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
- testcase( rc==SQLITE_NOMEM );
- TESTONLY( rc = ) addToSavepointBitvecs(pPager, pPg->pgno);
- testcase( rc==SQLITE_NOMEM );
- sqlite3EndBenignMalloc();
-
-
- PAGERTRACE(("DONT_ROLLBACK page %d of %d\n", pPg->pgno, PAGERID(pPager)));
- IOTRACE(("GARBAGE %p %d\n", pPager, pPg->pgno))
}
-
/*
** This routine is called to increment the database file change-counter,
** stored at byte 24 of the pager file.
put32bits(((char*)pPgHdr->pData)+24, change_counter);
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
- if( isDirect && pPager->fd->pMethods ){
+ if( isDirect && isOpen(pPager->fd) ){
const void *zBuf = pPgHdr->pData;
assert( pPager->dbFileSize>0 );
rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
*/
if( pPager->dbModified==0 &&
(pPager->journalMode!=PAGER_JOURNALMODE_DELETE ||
- pPager->exclusiveMode!=0) ){
- assert( pPager->dirtyCache==0 || pPager->journalOpen==0 );
+ pPager->exclusiveMode) ){
+ assert( pPager->dbModified==0 || !isOpen(pPager->jfd) );
return 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 && !MEMDB && pPager->dirtyCache ){
+ if( pPager->state!=PAGER_SYNCED && !MEMDB && pPager->dbModified ){
PgHdr *pPg;
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
pPg = sqlite3PcacheDirtyList(pPager->pPCache);
useAtomicWrite = (
!zMaster &&
- pPager->journalOpen &&
+ isOpen(pPager->jfd) &&
pPager->journalOff==jrnlBufferSize(pPager) &&
pPager->dbSize>=pPager->dbFileSize &&
(pPg==0 || pPg->pDirty==0)
);
- assert( pPager->journalOpen || pPager->journalMode==PAGER_JOURNALMODE_OFF );
+ assert( isOpen(pPager->jfd) || pPager->journalMode==PAGER_JOURNALMODE_OFF );
if( useAtomicWrite ){
/* Update the nRec field in the journal file. */
int offset = pPager->journalHdr + sizeof(aJournalMagic);
}
sqlite3PcacheCleanAll(pPager->pPCache);
- if( pPager->dbSize<pPager->dbFileSize ){
+ if( pPager->dbSize!=pPager->dbFileSize ){
+ Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
assert( pPager->state>=PAGER_EXCLUSIVE );
- rc = pager_truncate(pPager, pPager->dbSize);
+ rc = pager_truncate(pPager, nNew);
if( rc!=SQLITE_OK ) goto sync_exit;
}
if( pPager->dbModified==0 &&
(pPager->journalMode!=PAGER_JOURNALMODE_DELETE ||
pPager->exclusiveMode!=0) ){
- assert( pPager->dirtyCache==0 || pPager->journalOpen==0 );
+ assert( pPager->dbModified==0 || isOpen(pPager->jfd)==0 );
return SQLITE_OK;
}
PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
- assert( pPager->state==PAGER_SYNCED || MEMDB || !pPager->dirtyCache );
+ assert( pPager->state==PAGER_SYNCED || MEMDB || !pPager->dbModified );
rc = pager_end_transaction(pPager, pPager->setMaster);
rc = pager_error(pPager, rc);
return rc;
int sqlite3PagerRollback(Pager *pPager){
int rc = SQLITE_OK;
PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
- if( !pPager->dirtyCache || !pPager->journalOpen ){
+ if( !pPager->dbModified || !isOpen(pPager->jfd) ){
rc = pager_end_transaction(pPager, pPager->setMaster);
}else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
if( pPager->state>=PAGER_EXCLUSIVE ){
/* Either there is no active journal or the sub-journal is open or
** the journal is always stored in memory */
- assert( pPager->nSavepoint==0 || pPager->sjfd->pMethods ||
+ assert( pPager->nSavepoint==0 || isOpen(pPager->sjfd) ||
pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
/* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
for(/* no-op */; ii<nSavepoint; ii++){
assert( pPager->dbSizeValid );
aNew[ii].nOrig = pPager->dbSize;
- if( pPager->journalOpen && pPager->journalOff>0 ){
+ if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
aNew[ii].iOffset = pPager->journalOff;
}else{
aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
}
- aNew[ii].iSubRec = pPager->stmtNRec;
+ aNew[ii].iSubRec = pPager->nSubRec;
aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
if( !aNew[ii].pInSavepoint ){
return SQLITE_NOMEM;
}
pPager->nSavepoint = nNew;
- if( op==SAVEPOINT_ROLLBACK && pPager->jfd->pMethods ){
+ if( op==SAVEPOINT_ROLLBACK && isOpen(pPager->jfd) ){
PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
rc = pagerPlaybackSavepoint(pPager, pSavepoint);
assert(rc!=SQLITE_DONE);
/* If this is a release of the outermost savepoint, truncate
** the sub-journal. */
- if( nNew==0 && op==SAVEPOINT_RELEASE && pPager->sjfd->pMethods ){
+ if( nNew==0 && op==SAVEPOINT_RELEASE && isOpen(pPager->sjfd) ){
assert( rc==SQLITE_OK );
rc = sqlite3OsTruncate(pPager->sjfd, 0);
- pPager->stmtNRec = 0;
+ pPager->nSubRec = 0;
}
}
return rc;
return pPager->fd;
}
-/*
-** Return the directory of the database file.
-*/
-const char *sqlite3PagerDirname(Pager *pPager){
- return pPager->zDirectory;
-}
-
/*
** Return the full pathname of the journal file.
*/
PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
- pager_get_content(pPg);
-
/* If the journal needs to be sync()ed before page pPg->pgno can
** be written to, store pPg->pgno in local variable needSyncPgno.
**
}
sqlite3PcacheMakeDirty(pPg);
- pPager->dirtyCache = 1;
pPager->dbModified = 1;
if( needSyncPgno ){
** If the parameter is not _QUERY, then the journal-mode is set to the
** value specified.
**
-** The returned indicate the current (possibly updated)
-** journal-mode.
+** The returned indicate the current (possibly updated) journal-mode.
*/
int sqlite3PagerJournalMode(Pager *pPager, int eMode){
if( !MEMDB ){
projects / thirdparty / sqlite.git / commitdiff
