/*
** 2001 September 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This is the implementation of the page cache subsystem or "pager".
**
** The pager is used to access a database disk file. It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file. The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.355 2007/08/11 00:26:21 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
/*
** Macros for troubleshooting. Normally turned off
*/
#if 0
#define sqlite3DebugPrintf printf
#define PAGERTRACE1(X) sqlite3DebugPrintf(X)
#define PAGERTRACE2(X,Y) sqlite3DebugPrintf(X,Y)
#define PAGERTRACE3(X,Y,Z) sqlite3DebugPrintf(X,Y,Z)
#define PAGERTRACE4(X,Y,Z,W) sqlite3DebugPrintf(X,Y,Z,W)
#define PAGERTRACE5(X,Y,Z,W,V) sqlite3DebugPrintf(X,Y,Z,W,V)
#else
#define PAGERTRACE1(X)
#define PAGERTRACE2(X,Y)
#define PAGERTRACE3(X,Y,Z)
#define PAGERTRACE4(X,Y,Z,W)
#define PAGERTRACE5(X,Y,Z,W,V)
#endif
/*
** The following two macros are used within the PAGERTRACEX() macros above
** to print out file-descriptors.
**
** PAGERID() takes a pointer to a Pager struct as it's argument. The
** associated file-descriptor is returned. FILEHANDLEID() takes an OsFile
** struct as it's argument.
*/
#define PAGERID(p) ((int)(p->fd))
#define FILEHANDLEID(fd) ((int)fd)
/*
** The page cache as a whole is always in one of the following
** states:
**
** PAGER_UNLOCK The page cache is not currently reading or
** writing the database file. There is no
** data held in memory. This is the initial
** state.
**
** PAGER_SHARED The page cache is reading the database.
** Writing is not permitted. There can be
** multiple readers accessing the same database
** file at the same time.
**
** PAGER_RESERVED This process has reserved the database for writing
** but has not yet made any changes. Only one process
** at a time can reserve the database. The original
** database file has not been modified so other
** processes may still be reading the on-disk
** database file.
**
** PAGER_EXCLUSIVE The page cache is writing the database.
** Access is exclusive. No other processes or
** threads can be reading or writing while one
** process is writing.
**
** PAGER_SYNCED The pager moves to this state from PAGER_EXCLUSIVE
** after all dirty pages have been written to the
** database file and the file has been synced to
** disk. All that remains to do is to remove or
** truncate the journal file and the transaction
** will be committed.
**
** The page cache comes up in PAGER_UNLOCK. The first time a
** sqlite3PagerGet() occurs, the state transitions to PAGER_SHARED.
** After all pages have been released using sqlite_page_unref(),
** the state transitions back to PAGER_UNLOCK. The first time
** that sqlite3PagerWrite() is called, the state transitions to
** PAGER_RESERVED. (Note that sqlite3PagerWrite() can only be
** called on an outstanding page which means that the pager must
** be in PAGER_SHARED before it transitions to PAGER_RESERVED.)
** PAGER_RESERVED means that there is an open rollback journal.
** The transition to PAGER_EXCLUSIVE occurs before any changes
** are made to the database file, though writes to the rollback
** journal occurs with just PAGER_RESERVED. After an sqlite3PagerRollback()
** or sqlite3PagerCommitPhaseTwo(), the state can go back to PAGER_SHARED,
** or it can stay at PAGER_EXCLUSIVE if we are in exclusive access mode.
*/
#define PAGER_UNLOCK 0
#define PAGER_SHARED 1 /* same as SHARED_LOCK */
#define PAGER_RESERVED 2 /* same as RESERVED_LOCK */
#define PAGER_EXCLUSIVE 4 /* same as EXCLUSIVE_LOCK */
#define PAGER_SYNCED 5
/*
** If the SQLITE_BUSY_RESERVED_LOCK macro is set to true at compile-time,
** then failed attempts to get a reserved lock will invoke the busy callback.
** This is off by default. To see why, consider the following scenario:
**
** Suppose thread A already has a shared lock and wants a reserved lock.
** Thread B already has a reserved lock and wants an exclusive lock. If
** both threads are using their busy callbacks, it might be a long time
** be for one of the threads give up and allows the other to proceed.
** But if the thread trying to get the reserved lock gives up quickly
** (if it never invokes its busy callback) then the contention will be
** resolved quickly.
*/
#ifndef SQLITE_BUSY_RESERVED_LOCK
# define SQLITE_BUSY_RESERVED_LOCK 0
#endif
/*
** This macro rounds values up so that if the value is an address it
** is guaranteed to be an address that is aligned to an 8-byte boundary.
*/
#define FORCE_ALIGNMENT(X) (((X)+7)&~7)
/*
** Each in-memory image of a page begins with the following header.
** This header is only visible to this pager module. The client
** code that calls pager sees only the data that follows the header.
**
** Client code should call sqlite3PagerWrite() on a page prior to making
** any modifications to that page. The first time sqlite3PagerWrite()
** is called, the original page contents are written into the rollback
** journal and PgHdr.inJournal and PgHdr.needSync are set. Later, once
** the journal page has made it onto the disk surface, PgHdr.needSync
** is cleared. The modified page cannot be written back into the original
** database file until the journal pages has been synced to disk and the
** PgHdr.needSync has been cleared.
**
** The PgHdr.dirty flag is set when sqlite3PagerWrite() is called and
** is cleared again when the page content is written back to the original
** database file.
**
** Details of important structure elements:
**
** needSync
**
** If this is true, this means that it is not safe to write the page
** content to the database because the original content needed
** for rollback has not by synced to the main rollback journal.
** The original content may have been written to the rollback journal
** but it has not yet been synced. So we cannot write to the database
** file because power failure might cause the page in the journal file
** to never reach the disk. It is as if the write to the journal file
** does not occur until the journal file is synced.
**
** This flag is false if the page content exactly matches what
** currently exists in the database file. The needSync flag is also
** false if the original content has been written to the main rollback
** journal and synced. If the page represents a new page that has
** been added onto the end of the database during the current
** transaction, the needSync flag is true until the original database
** size in the journal header has been synced to disk.
**
** inJournal
**
** This is true if the original page has been written into the main
** rollback journal. This is always false for new pages added to
** the end of the database file during the current transaction.
** And this flag says nothing about whether or not the journal
** has been synced to disk. For pages that are in the original
** database file, the following expression should always be true:
**
** inJournal = (pPager->aInJournal[(pgno-1)/8] & (1<<((pgno-1)%8))!=0
**
** The pPager->aInJournal[] array is only valid for the original
** pages of the database, not new pages that are added to the end
** of the database, so obviously the above expression cannot be
** valid for new pages. For new pages inJournal is always 0.
**
** dirty
**
** When true, this means that the content of the page has been
** modified and needs to be written back to the database file.
** If false, it means that either the content of the page is
** unchanged or else the content is unimportant and we do not
** care whether or not it is preserved.
**
** alwaysRollback
**
** This means that the sqlite3PagerDontRollback() API should be
** ignored for this page. The DontRollback() API attempts to say
** that the content of the page on disk is unimportant (it is an
** unused page on the freelist) so that it is unnecessary to
** rollback changes to this page because the content of the page
** can change without changing the meaning of the database. This
** flag overrides any DontRollback() attempt. This flag is set
** when a page that originally contained valid data is added to
** the freelist. Later in the same transaction, this page might
** be pulled from the freelist and reused for something different
** and at that point the DontRollback() API will be called because
** pages taken from the freelist do not need to be protected by
** the rollback journal. But this flag says that the page was
** not originally part of the freelist so that it still needs to
** be rolled back in spite of any subsequent DontRollback() calls.
**
** needRead
**
** This flag means (when true) that the content of the page has
** not yet been loaded from disk. The in-memory content is just
** garbage. (Actually, we zero the content, but you should not
** make any assumptions about the content nevertheless.) If the
** content is needed in the future, it should be read from the
** original database file.
*/
typedef struct PgHdr PgHdr;
struct PgHdr {
Pager *pPager; /* The pager to which this page belongs */
Pgno pgno; /* The page number for this page */
PgHdr *pNextHash, *pPrevHash; /* Hash collision chain for PgHdr.pgno */
PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */
PgHdr *pNextAll; /* A list of all pages */
u8 inJournal; /* TRUE if has been written to journal */
u8 dirty; /* TRUE if we need to write back changes */
u8 needSync; /* Sync journal before writing this page */
u8 alwaysRollback; /* Disable DontRollback() for this page */
u8 needRead; /* Read content if PagerWrite() is called */
short int nRef; /* Number of users of this page */
PgHdr *pDirty, *pPrevDirty; /* Dirty pages */
u32 notUsed; /* Buffer space */
#ifdef SQLITE_CHECK_PAGES
u32 pageHash;
#endif
/* pPager->pageSize bytes of page data follow this header */
/* Pager.nExtra bytes of local data follow the page data */
};
/*
** For an in-memory only database, some extra information is recorded about
** each page so that changes can be rolled back. (Journal files are not
** used for in-memory databases.) The following information is added to
** the end of every EXTRA block for in-memory databases.
**
** This information could have been added directly to the PgHdr structure.
** But then it would take up an extra 8 bytes of storage on every PgHdr
** even for disk-based databases. Splitting it out saves 8 bytes. This
** is only a savings of 0.8% but those percentages add up.
*/
typedef struct PgHistory PgHistory;
struct PgHistory {
u8 *pOrig; /* Original page text. Restore to this on a full rollback */
u8 *pStmt; /* Text as it was at the beginning of the current statement */
PgHdr *pNextStmt, *pPrevStmt; /* List of pages in the statement journal */
u8 inStmt; /* TRUE if in the statement subjournal */
};
/*
** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC
# define CODEC1(P,D,N,X) if( P->xCodec!=0 ){ P->xCodec(P->pCodecArg,D,N,X); }
# define CODEC2(P,D,N,X) ((char*)(P->xCodec!=0?P->xCodec(P->pCodecArg,D,N,X):D))
#else
# define CODEC1(P,D,N,X) /* NO-OP */
# define CODEC2(P,D,N,X) ((char*)D)
#endif
/*
** Convert a pointer to a PgHdr into a pointer to its data
** and back again.
*/
#define PGHDR_TO_DATA(P) ((void*)(&(P)[1]))
#define DATA_TO_PGHDR(D) (&((PgHdr*)(D))[-1])
#define PGHDR_TO_EXTRA(G,P) ((void*)&((char*)(&(G)[1]))[(P)->pageSize])
#define PGHDR_TO_HIST(P,PGR) \
((PgHistory*)&((char*)(&(P)[1]))[(PGR)->pageSize+(PGR)->nExtra])
/*
** A open page cache is an instance of the following structure.
**
** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or
** or SQLITE_FULL. Once one of the first three errors occurs, it persists
** and is returned as the result of every major pager API call. The
** SQLITE_FULL return code is slightly different. It persists only until the
** next successful rollback is performed on the pager cache. Also,
** SQLITE_FULL does not affect the sqlite3PagerGet() and sqlite3PagerLookup()
** APIs, they may still be used successfully.
*/
struct Pager {
u8 journalOpen; /* True if journal file descriptors is valid */
u8 journalStarted; /* True if header of journal is synced */
u8 useJournal; /* Use a rollback journal on this file */
u8 noReadlock; /* Do not bother to obtain readlocks */
u8 stmtOpen; /* True if the statement subjournal is open */
u8 stmtInUse; /* True we are in a statement subtransaction */
u8 stmtAutoopen; /* Open stmt journal when main journal is opened*/
u8 noSync; /* Do not sync the journal if true */
u8 fullSync; /* Do extra syncs of the journal for robustness */
u8 full_fsync; /* Use F_FULLFSYNC when available */
u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */
u8 tempFile; /* zFilename is a temporary file */
u8 readOnly; /* True for a read-only database */
u8 needSync; /* True if an fsync() is needed on the journal */
u8 dirtyCache; /* True if cached pages have changed */
u8 alwaysRollback; /* Disable DontRollback() for all pages */
u8 memDb; /* True to inhibit all file I/O */
u8 setMaster; /* True if a m-j name has been written to jrnl */
u8 doNotSync; /* Boolean. While true, do not spill the cache */
u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
u8 changeCountDone; /* Set after incrementing the change-counter */
int errCode; /* One of several kinds of errors */
int dbSize; /* Number of pages in the file */
int origDbSize; /* dbSize before the current change */
int stmtSize; /* Size of database (in pages) at stmt_begin() */
int nRec; /* Number of pages written to the journal */
u32 cksumInit; /* Quasi-random value added to every checksum */
int stmtNRec; /* Number of records in stmt subjournal */
int nExtra; /* Add this many bytes to each in-memory page */
int pageSize; /* Number of bytes in a page */
int nPage; /* Total number of in-memory pages */
int nRef; /* Number of in-memory pages with PgHdr.nRef>0 */
int mxPage; /* Maximum number of pages to hold in cache */
Pgno mxPgno; /* Maximum allowed size of the database */
u8 *aInJournal; /* One bit for each page in the database file */
u8 *aInStmt; /* One bit for each page in the database */
char *zFilename; /* Name of the database file */
char *zJournal; /* Name of the journal file */
char *zDirectory; /* Directory hold database and journal files */
OsFile *fd, *jfd; /* File descriptors for database and journal */
OsFile *stfd; /* File descriptor for the statement subjournal*/
BusyHandler *pBusyHandler; /* Pointer to sqlite.busyHandler */
PgHdr *pFirst, *pLast; /* List of free pages */
PgHdr *pFirstSynced; /* First free page with PgHdr.needSync==0 */
PgHdr *pAll; /* List of all pages */
PgHdr *pStmt; /* List of pages in the statement subjournal */
PgHdr *pDirty; /* List of all dirty pages */
i64 journalOff; /* Current byte offset in the journal file */
i64 journalHdr; /* Byte offset to previous journal header */
i64 stmtHdrOff; /* First journal header written this statement */
i64 stmtCksum; /* cksumInit when statement was started */
i64 stmtJSize; /* Size of journal at stmt_begin() */
int sectorSize; /* Assumed sector size during rollback */
#ifdef SQLITE_TEST
int nHit, nMiss; /* Cache hits and missing */
int nRead, nWrite; /* Database pages read/written */
#endif
void (*xDestructor)(DbPage*,int); /* Call this routine when freeing pages */
void (*xReiniter)(DbPage*,int); /* Call this routine when reloading pages */
#ifdef SQLITE_HAS_CODEC
void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
void *pCodecArg; /* First argument to xCodec() */
#endif
int nHash; /* Size of the pager hash table */
PgHdr **aHash; /* Hash table to map page number to PgHdr */
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
Pager *pNext; /* Linked list of pagers in this thread */
#endif
char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */
char dbFileVers[16]; /* Changes whenever database file changes */
};
/*
** The following global variables hold counters used for
** testing purposes only. These variables do not exist in
** a non-testing build. These variables are not thread-safe.
*/
#ifdef SQLITE_TEST
int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */
int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */
int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */
int sqlite3_pager_pgfree_count = 0; /* Number of cache pages freed */
# define PAGER_INCR(v) v++
#else
# define PAGER_INCR(v)
#endif
/*
** Journal files begin with the following magic string. The data
** was obtained from /dev/random. It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
** checking information. If the power fails while the journal is begin
** written, semi-random garbage data might appear in the journal
** file after power is restored. If an attempt is then made
** to roll the journal back, the database could be corrupted. The additional
** sanity checking data is an attempt to discover the garbage in the
** journal and ignore it.
**
** The sanity checking information for the new journal format consists
** of a 32-bit checksum on each page of data. The checksum covers both
** the page number and the pPager->pageSize bytes of data for the page.
** This cksum is initialized to a 32-bit random value that appears in the
** journal file right after the header. The random initializer is important,
** because garbage data that appears at the end of a journal is likely
** data that was once in other files that have now been deleted. If the
** garbage data came from an obsolete journal file, the checksums might
** be correct. But by initializing the checksum to random value which
** is different for every journal, we minimize that risk.
*/
static const unsigned char aJournalMagic[] = {
0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
};
/*
** The size of the header and of each page in the journal is determined
** by the following macros.
*/
#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8)
/*
** The journal header size for this pager. In the future, this could be
** set to some value read from the disk controller. The important
** characteristic is that it is the same size as a disk sector.
*/
#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
/*
** The macro MEMDB is true if we are dealing with an in-memory database.
** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
** the value of MEMDB will be a constant and the compiler will optimize
** out code that would never execute.
*/
#ifdef SQLITE_OMIT_MEMORYDB
# define MEMDB 0
#else
# define MEMDB pPager->memDb
#endif
/*
** Page number PAGER_MJ_PGNO is never used in an SQLite database (it is
** reserved for working around a windows/posix incompatibility). It is
** used in the journal to signify that the remainder of the journal file
** is devoted to storing a master journal name - there are no more pages to
** roll back. See comments for function writeMasterJournal() for details.
*/
/* #define PAGER_MJ_PGNO(x) (PENDING_BYTE/((x)->pageSize)) */
#define PAGER_MJ_PGNO(x) ((PENDING_BYTE/((x)->pageSize))+1)
/*
** The maximum legal page number is (2^31 - 1).
*/
#define PAGER_MAX_PGNO 2147483647
/*
** Enable reference count tracking (for debugging) here:
*/
#ifdef SQLITE_DEBUG
int pager3_refinfo_enable = 0;
static void pager_refinfo(PgHdr *p){
static int cnt = 0;
if( !pager3_refinfo_enable ) return;
sqlite3DebugPrintf(
"REFCNT: %4d addr=%p nRef=%-3d total=%d\n",
p->pgno, PGHDR_TO_DATA(p), p->nRef, p->pPager->nRef
);
cnt++; /* Something to set a breakpoint on */
}
# define REFINFO(X) pager_refinfo(X)
#else
# define REFINFO(X)
#endif
/*
** Return true if page *pPg has already been written to the statement
** journal (or statement snapshot has been created, if *pPg is part
** of an in-memory database).
*/
static int pageInStatement(PgHdr *pPg){
Pager *pPager = pPg->pPager;
if( MEMDB ){
return PGHDR_TO_HIST(pPg, pPager)->inStmt;
}else{
Pgno pgno = pPg->pgno;
u8 *a = pPager->aInStmt;
return (a && (int)pgno<=pPager->stmtSize && (a[pgno/8] & (1<<(pgno&7))));
}
}
/*
** Change the size of the pager hash table to N. N must be a power
** of two.
*/
static void pager_resize_hash_table(Pager *pPager, int N){
PgHdr **aHash, *pPg;
assert( N>0 && (N&(N-1))==0 );
aHash = sqliteMalloc( sizeof(aHash[0])*N );
if( aHash==0 ){
/* Failure to rehash is not an error. It is only a performance hit. */
return;
}
sqliteFree(pPager->aHash);
pPager->nHash = N;
pPager->aHash = aHash;
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
int h;
if( pPg->pgno==0 ){
assert( pPg->pNextHash==0 && pPg->pPrevHash==0 );
continue;
}
h = pPg->pgno & (N-1);
pPg->pNextHash = aHash[h];
if( aHash[h] ){
aHash[h]->pPrevHash = pPg;
}
aHash[h] = pPg;
pPg->pPrevHash = 0;
}
}
/*
** Read a 32-bit integer from the given file descriptor. Store the integer
** that is read in *pRes. Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
*/
static int read32bits(OsFile *fd, u32 *pRes){
unsigned char ac[4];
int rc = sqlite3OsRead(fd, ac, sizeof(ac));
if( rc==SQLITE_OK ){
*pRes = sqlite3Get4byte(ac);
}
return rc;
}
/*
** Write a 32-bit integer into a string buffer in big-endian byte order.
*/
#define put32bits(A,B) sqlite3Put4byte((u8*)A,B)
/*
** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK
** on success or an error code is something goes wrong.
*/
static int write32bits(OsFile *fd, u32 val){
char ac[4];
put32bits(ac, val);
return sqlite3OsWrite(fd, ac, 4);
}
/*
** This function should be called when an error occurs within the pager
** code. The first argument is a pointer to the pager structure, the
** second the error-code about to be returned by a pager API function.
** The value returned is a copy of the second argument to this function.
**
** If the second argument is SQLITE_IOERR, SQLITE_CORRUPT, or SQLITE_FULL
** the error becomes persistent. All subsequent API calls on this Pager
** will immediately return the same error code.
*/
static int pager_error(Pager *pPager, int rc){
int rc2 = rc & 0xff;
assert(
pPager->errCode==SQLITE_FULL ||
pPager->errCode==SQLITE_OK ||
(pPager->errCode & 0xff)==SQLITE_IOERR
);
if(
rc2==SQLITE_FULL ||
rc2==SQLITE_IOERR ||
rc2==SQLITE_CORRUPT
){
pPager->errCode = rc;
}
return rc;
}
/*
** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
** on the cache using a hash function. This is used for testing
** and debugging only.
*/
#ifdef SQLITE_CHECK_PAGES
/*
** Return a 32-bit hash of the page data for pPage.
*/
static u32 pager_datahash(int nByte, unsigned char *pData){
u32 hash = 0;
int i;
for(i=0; i<nByte; i++){
hash = (hash*1039) + pData[i];
}
return hash;
}
static u32 pager_pagehash(PgHdr *pPage){
return pager_datahash(pPage->pPager->pageSize,
(unsigned char *)PGHDR_TO_DATA(pPage));
}
/*
** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
** is defined, and NDEBUG is not defined, an assert() statement checks
** that the page is either dirty or still matches the calculated page-hash.
*/
#define CHECK_PAGE(x) checkPage(x)
static void checkPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
assert( !pPg->pageHash || pPager->errCode || MEMDB || pPg->dirty ||
pPg->pageHash==pager_pagehash(pPg) );
}
#else
#define pager_datahash(X,Y) 0
#define pager_pagehash(X) 0
#define CHECK_PAGE(x)
#endif
/*
** When this is called the journal file for pager pPager must be open.
** The master journal file name is read from the end of the file and
** written into memory obtained from sqliteMalloc(). *pzMaster is
** set to point at the memory and SQLITE_OK returned. The caller must
** sqliteFree() *pzMaster.
**
** If no master journal file name is present *pzMaster is set to 0 and
** SQLITE_OK returned.
*/
static int readMasterJournal(OsFile *pJrnl, char **pzMaster){
int rc;
u32 len;
i64 szJ;
u32 cksum;
int i;
unsigned char aMagic[8]; /* A buffer to hold the magic header */
*pzMaster = 0;
rc = sqlite3OsFileSize(pJrnl, &szJ);
if( rc!=SQLITE_OK || szJ<16 ) return rc;
rc = sqlite3OsSeek(pJrnl, szJ-16);
if( rc!=SQLITE_OK ) return rc;
rc = read32bits(pJrnl, &len);
if( rc!=SQLITE_OK ) return rc;
rc = read32bits(pJrnl, &cksum);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(pJrnl, aMagic, 8);
if( rc!=SQLITE_OK || memcmp(aMagic, aJournalMagic, 8) ) return rc;
rc = sqlite3OsSeek(pJrnl, szJ-16-len);
if( rc!=SQLITE_OK ) return rc;
*pzMaster = (char *)sqliteMalloc(len+1);
if( !*pzMaster ){
return SQLITE_NOMEM;
}
rc = sqlite3OsRead(pJrnl, *pzMaster, len);
if( rc!=SQLITE_OK ){
sqliteFree(*pzMaster);
*pzMaster = 0;
return rc;
}
/* See if the checksum matches the master journal name */
for(i=0; i<len; i++){
cksum -= (*pzMaster)[i];
}
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.
*/
sqliteFree(*pzMaster);
*pzMaster = 0;
}else{
(*pzMaster)[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.
**
** i.e for a sector size of 512:
**
** Input Offset Output Offset
** ---------------------------------------
** 0 0
** 512 512
** 100 512
** 2000 2048
**
*/
static int seekJournalHdr(Pager *pPager){
i64 offset = 0;
i64 c = pPager->journalOff;
if( c ){
offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
}
assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
assert( offset>=c );
assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
pPager->journalOff = offset;
return sqlite3OsSeek(pPager->jfd, pPager->journalOff);
}
/*
** The journal file must be open when this routine is called. A journal
** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
** current location.
**
** The format for the journal header is as follows:
** - 8 bytes: Magic identifying journal format.
** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
** - 4 bytes: Random number used for page hash.
** - 4 bytes: Initial database page count.
** - 4 bytes: Sector size used by the process that wrote this journal.
**
** Followed by (JOURNAL_HDR_SZ - 24) bytes of unused space.
*/
static int writeJournalHdr(Pager *pPager){
char zHeader[sizeof(aJournalMagic)+16];
int rc;
if( pPager->stmtHdrOff==0 ){
pPager->stmtHdrOff = pPager->journalOff;
}
rc = seekJournalHdr(pPager);
if( rc ) return rc;
pPager->journalHdr = pPager->journalOff;
pPager->journalOff += JOURNAL_HDR_SZ(pPager);
/* FIX ME:
**
** Possibly for a pager not in no-sync mode, the journal magic should not
** be written until nRec is filled in as part of next syncJournal().
**
** Actually maybe the whole journal header should be delayed until that
** point. Think about this.
*/
memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
/* The nRec Field. 0xFFFFFFFF for no-sync journals. */
put32bits(&zHeader[sizeof(aJournalMagic)], pPager->noSync ? 0xffffffff : 0);
/* The random check-hash initialiser */
sqlite3Randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
/* The initial database size */
put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbSize);
/* The assumed sector size for this process */
put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, sizeof(zHeader)))
rc = sqlite3OsWrite(pPager->jfd, zHeader, sizeof(zHeader));
/* The journal header has been written successfully. Seek the journal
** file descriptor to the end of the journal header sector.
*/
if( rc==SQLITE_OK ){
IOTRACE(("JTAIL %p %lld\n", pPager, pPager->journalOff-1))
rc = sqlite3OsSeek(pPager->jfd, pPager->journalOff-1);
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->jfd, "\000", 1);
}
}
return rc;
}
/*
** The journal file must be open when this is called. A journal header file
** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
** file. See comments above function writeJournalHdr() for a description of
** the journal header format.
**
** If the header is read successfully, *nRec is set to the number of
** page records following this header and *dbSize is set to the size of the
** database before the transaction began, in pages. Also, pPager->cksumInit
** is set to the value read from the journal header. SQLITE_OK is returned
** in this case.
**
** If the journal header file appears to be corrupted, SQLITE_DONE is
** returned and *nRec and *dbSize are not set. If JOURNAL_HDR_SZ bytes
** cannot be read from the journal file an error code is returned.
*/
static int readJournalHdr(
Pager *pPager,
i64 journalSize,
u32 *pNRec,
u32 *pDbSize
){
int rc;
unsigned char aMagic[8]; /* A buffer to hold the magic header */
rc = seekJournalHdr(pPager);
if( rc ) return rc;
if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
return SQLITE_DONE;
}
rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic));
if( rc ) return rc;
if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
return SQLITE_DONE;
}
rc = read32bits(pPager->jfd, pNRec);
if( rc ) return rc;
rc = read32bits(pPager->jfd, &pPager->cksumInit);
if( rc ) return rc;
rc = read32bits(pPager->jfd, pDbSize);
if( rc ) return rc;
/* Update the assumed sector-size to match the value used by
** the process that created this journal. If this journal was
** created by a process other than this one, then this routine
** is being called from within pager_playback(). The local value
** of Pager.sectorSize is restored at the end of that routine.
*/
rc = read32bits(pPager->jfd, (u32 *)&pPager->sectorSize);
if( rc ) return rc;
pPager->journalOff += JOURNAL_HDR_SZ(pPager);
rc = sqlite3OsSeek(pPager->jfd, pPager->journalOff);
return rc;
}
/*
** Write the supplied master journal name into the journal file for pager
** pPager at the current location. The master journal name must be the last
** thing written to a journal file. If the pager is in full-sync mode, the
** journal file descriptor is advanced to the next sector boundary before
** anything is written. The format is:
**
** + 4 bytes: PAGER_MJ_PGNO.
** + N bytes: length of master journal name.
** + 4 bytes: N
** + 4 bytes: Master journal name checksum.
** + 8 bytes: aJournalMagic[].
**
** The master journal page checksum is the sum of the bytes in the master
** journal name.
**
** 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;
u32 cksum = 0;
char zBuf[sizeof(aJournalMagic)+2*4];
if( !zMaster || pPager->setMaster) return SQLITE_OK;
pPager->setMaster = 1;
len = strlen(zMaster);
for(i=0; i<len; i++){
cksum += zMaster[i];
}
/* If in full-sync mode, advance to the next disk sector before writing
** the master journal name. This is in case the previous page written to
** the journal has already been synced.
*/
if( pPager->fullSync ){
rc = seekJournalHdr(pPager);
if( rc!=SQLITE_OK ) return rc;
}
pPager->journalOff += (len+20);
rc = write32bits(pPager->jfd, PAGER_MJ_PGNO(pPager));
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsWrite(pPager->jfd, zMaster, len);
if( rc!=SQLITE_OK ) return rc;
put32bits(zBuf, len);
put32bits(&zBuf[4], cksum);
memcpy(&zBuf[8], aJournalMagic, sizeof(aJournalMagic));
rc = sqlite3OsWrite(pPager->jfd, zBuf, 8+sizeof(aJournalMagic));
pPager->needSync = !pPager->noSync;
return rc;
}
/*
** Add or remove a page from the list of all pages that are in the
** statement journal.
**
** The Pager keeps a separate list of pages that are currently in
** the statement journal. This helps the sqlite3PagerStmtCommit()
** routine run MUCH faster for the common case where there are many
** pages in memory but only a few are in the statement journal.
*/
static void page_add_to_stmt_list(PgHdr *pPg){
Pager *pPager = pPg->pPager;
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
assert( MEMDB );
if( !pHist->inStmt ){
assert( pHist->pPrevStmt==0 && pHist->pNextStmt==0 );
if( pPager->pStmt ){
PGHDR_TO_HIST(pPager->pStmt, pPager)->pPrevStmt = pPg;
}
pHist->pNextStmt = pPager->pStmt;
pPager->pStmt = pPg;
pHist->inStmt = 1;
}
}
/*
** Find a page in the hash table given its page number. Return
** a pointer to the page or NULL if not found.
*/
static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
PgHdr *p;
if( pPager->aHash==0 ) return 0;
p = pPager->aHash[pgno & (pPager->nHash-1)];
while( p && p->pgno!=pgno ){
p = p->pNextHash;
}
return p;
}
/*
** Unlock the database file.
*/
static void pager_unlock(Pager *pPager){
if( !pPager->exclusiveMode ){
if( !MEMDB ){
sqlite3OsUnlock(pPager->fd, NO_LOCK);
pPager->dbSize = -1;
IOTRACE(("UNLOCK %p\n", pPager))
}
pPager->state = PAGER_UNLOCK;
pPager->changeCountDone = 0;
}
}
/*
** Execute a rollback if a transaction is active and unlock the
** database file. This is a no-op if the pager has already entered
** the error-state.
*/
static void pagerUnlockAndRollback(Pager *p){
if( p->errCode ) return;
assert( p->state>=PAGER_RESERVED || p->journalOpen==0 );
if( p->state>=PAGER_RESERVED ){
sqlite3PagerRollback(p);
}
pager_unlock(p);
assert( p->errCode || !p->journalOpen || (p->exclusiveMode&&!p->journalOff) );
assert( p->errCode || !p->stmtOpen || p->exclusiveMode );
}
/*
** Clear the in-memory cache. This routine
** sets the state of the pager back to what it was when it was first
** opened. Any outstanding pages are invalidated and subsequent attempts
** to access those pages will likely result in a coredump.
*/
static void pager_reset(Pager *pPager){
PgHdr *pPg, *pNext;
if( pPager->errCode ) return;
for(pPg=pPager->pAll; pPg; pPg=pNext){
IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
PAGER_INCR(sqlite3_pager_pgfree_count);
pNext = pPg->pNextAll;
sqliteFree(pPg);
}
pPager->pStmt = 0;
pPager->pFirst = 0;
pPager->pFirstSynced = 0;
pPager->pLast = 0;
pPager->pAll = 0;
pPager->nHash = 0;
sqliteFree(pPager->aHash);
pPager->nPage = 0;
pPager->aHash = 0;
pPager->nRef = 0;
}
/*
** This routine ends a transaction. A transaction is ended by either
** a COMMIT or a ROLLBACK.
**
** When this routine is called, the pager has the journal file open and
** a RESERVED or EXCLUSIVE lock on the database. This routine will release
** the database lock and acquires a SHARED lock in its place if that is
** the appropriate thing to do. Release locks usually is appropriate,
** unless we are in exclusive access mode or unless this is a
** COMMIT AND BEGIN or ROLLBACK AND BEGIN operation.
**
** The journal file is either deleted or truncated.
**
** TODO: Consider keeping the journal file open for temporary databases.
** This might give a performance improvement on windows where opening
** a file is an expensive operation.
*/
static int pager_end_transaction(Pager *pPager){
PgHdr *pPg;
int rc = SQLITE_OK;
int rc2 = SQLITE_OK;
assert( !MEMDB );
if( pPager->state<PAGER_RESERVED ){
return SQLITE_OK;
}
sqlite3PagerStmtCommit(pPager);
if( pPager->stmtOpen && !pPager->exclusiveMode ){
sqlite3OsClose(&pPager->stfd);
pPager->stmtOpen = 0;
}
if( pPager->journalOpen ){
if( pPager->exclusiveMode
&& (rc = sqlite3OsTruncate(pPager->jfd, 0))==SQLITE_OK ){;
sqlite3OsSeek(pPager->jfd, 0);
pPager->journalOff = 0;
pPager->journalStarted = 0;
}else{
sqlite3OsClose(&pPager->jfd);
pPager->journalOpen = 0;
if( rc==SQLITE_OK ){
rc = sqlite3OsDelete(pPager->zJournal);
}
}
sqliteFree( pPager->aInJournal );
pPager->aInJournal = 0;
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
pPg->inJournal = 0;
pPg->dirty = 0;
pPg->needSync = 0;
pPg->alwaysRollback = 0;
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
}
pPager->pDirty = 0;
pPager->dirtyCache = 0;
pPager->nRec = 0;
}else{
assert( pPager->aInJournal==0 );
assert( pPager->dirtyCache==0 || pPager->useJournal==0 );
}
if( !pPager->exclusiveMode ){
rc2 = sqlite3OsUnlock(pPager->fd, SHARED_LOCK);
pPager->state = PAGER_SHARED;
}else if( pPager->state==PAGER_SYNCED ){
pPager->state = PAGER_EXCLUSIVE;
}
pPager->origDbSize = 0;
pPager->setMaster = 0;
pPager->needSync = 0;
pPager->pFirstSynced = pPager->pFirst;
pPager->dbSize = -1;
return (rc==SQLITE_OK?rc2:rc);
}
/*
** Compute and return a checksum for the page of data.
**
** This is not a real checksum. It is really just the sum of the
** random initial value and the page number. We experimented with
** a checksum of the entire data, but that was found to be too slow.
**
** Note that the page number is stored at the beginning of data and
** the checksum is stored at the end. This is important. If journal
** corruption occurs due to a power failure, the most likely scenario
** is that one end or the other of the record will be changed. It is
** much less likely that the two ends of the journal record will be
** correct and the middle be corrupt. Thus, this "checksum" scheme,
** though fast and simple, catches the mostly likely kind of corruption.
**
** FIX ME: Consider adding every 200th (or so) byte of the data to the
** checksum. That way if a single page spans 3 or more disk sectors and
** only the middle sector is corrupt, we will still have a reasonable
** chance of failing the checksum and thus detecting the problem.
*/
static u32 pager_cksum(Pager *pPager, const u8 *aData){
u32 cksum = pPager->cksumInit;
int i = pPager->pageSize-200;
while( i>0 ){
cksum += aData[i];
i -= 200;
}
return cksum;
}
/* Forward declaration */
static void makeClean(PgHdr*);
/*
** Read a single page from the journal file opened on file descriptor
** jfd. Playback this one page.
**
** If useCksum==0 it means this journal does not use checksums. Checksums
** are not used in statement journals because statement journals do not
** need to survive power failures.
*/
static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int useCksum){
int rc;
PgHdr *pPg; /* An existing page in the cache */
Pgno pgno; /* The page number of a page in journal */
u32 cksum; /* Checksum used for sanity checking */
u8 *aData = (u8 *)pPager->pTmpSpace; /* Temp storage for a page */
/* useCksum should be true for the main journal and false for
** statement journals. Verify that this is always the case
*/
assert( jfd == (useCksum ? pPager->jfd : pPager->stfd) );
assert( aData );
rc = read32bits(jfd, &pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(jfd, aData, pPager->pageSize);
if( rc!=SQLITE_OK ) return rc;
pPager->journalOff += pPager->pageSize + 4;
/* Sanity checking on the page. This is more important that I originally
** thought. If a power failure occurs while the journal is being written,
** it could cause invalid data to be written into the journal. We need to
** detect this invalid data (with high probability) and ignore it.
*/
if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
return SQLITE_DONE;
}
if( pgno>(unsigned)pPager->dbSize ){
return SQLITE_OK;
}
if( useCksum ){
rc = read32bits(jfd, &cksum);
if( rc ) return rc;
pPager->journalOff += 4;
if( pager_cksum(pPager, aData)!=cksum ){
return SQLITE_DONE;
}
}
assert( pPager->state==PAGER_RESERVED || pPager->state>=PAGER_EXCLUSIVE );
/* If the pager is in RESERVED state, then there must be a copy of this
** page in the pager cache. In this case just update the pager cache,
** not the database file. The page is left marked dirty in this case.
**
** An exception to the above rule: If the database is in no-sync mode
** and a page is moved during an incremental vacuum then the page may
** not be in the pager cache. Later: if a malloc() or IO error occurs
** during a Movepage() call, then the page may not be in the cache
** either. So the condition described in the above paragraph is not
** assert()able.
**
** If in EXCLUSIVE state, then we update the pager cache if it exists
** and the main file. The page is then marked not dirty.
**
** Ticket #1171: The statement journal might contain page content that is
** different from the page content at the start of the transaction.
** This occurs when a page is changed prior to the start of a statement
** then changed again within the statement. When rolling back such a
** statement we must not write to the original database unless we know
** for certain that original page contents are synced into the main rollback
** journal. Otherwise, a power loss might leave modified data in the
** database file without an entry in the rollback journal that can
** restore the database to its original form. Two conditions must be
** met before writing to the database files. (1) the database must be
** locked. (2) we know that the original page content is fully synced
** in the main journal either because the page is not in cache or else
** the page is marked as needSync==0.
*/
pPg = pager_lookup(pPager, pgno);
PAGERTRACE4("PLAYBACK %d page %d hash(%08x)\n",
PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, aData));
if( pPager->state>=PAGER_EXCLUSIVE && (pPg==0 || pPg->needSync==0) ){
rc = sqlite3OsSeek(pPager->fd, (pgno-1)*(i64)pPager->pageSize);
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize);
}
if( pPg ){
makeClean(pPg);
}
}
if( pPg ){
/* No page should ever be explicitly rolled back that is in use, except
** for page 1 which is held in use in order to keep the lock on the
** database active. However such a page may be rolled back as a result
** of an internal error resulting in an automatic call to
** sqlite3PagerRollback().
*/
void *pData;
/* assert( pPg->nRef==0 || pPg->pgno==1 ); */
pData = PGHDR_TO_DATA(pPg);
memcpy(pData, aData, pPager->pageSize);
if( pPager->xReiniter ){
pPager->xReiniter(pPg, pPager->pageSize);
}
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
/* If this was page 1, then restore the value of Pager.dbFileVers.
** Do this before any decoding. */
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
}
/* Decode the page just read from disk */
CODEC1(pPager, pData, pPg->pgno, 3);
}
return rc;
}
/*
** Parameter zMaster is the name of a master journal file. A single journal
** file that referred to the master journal file has just been rolled back.
** This routine checks if it is possible to delete the master journal file,
** and does so if it is.
**
** The master journal file contains the names of all child journals.
** To tell if a master journal can be deleted, check to each of the
** children. If all children are either missing or do not refer to
** a different master journal, then this master journal can be deleted.
*/
static int pager_delmaster(const char *zMaster){
int rc;
int master_open = 0;
OsFile *master = 0;
char *zMasterJournal = 0; /* Contents of master journal file */
i64 nMasterJournal; /* Size of master journal file */
/* Open the master journal file exclusively in case some other process
** is running this routine also. Not that it makes too much difference.
*/
rc = sqlite3OsOpenReadOnly(zMaster, &master);
assert( rc!=SQLITE_OK || master );
if( rc!=SQLITE_OK ) goto delmaster_out;
master_open = 1;
rc = sqlite3OsFileSize(master, &nMasterJournal);
if( rc!=SQLITE_OK ) goto delmaster_out;
if( nMasterJournal>0 ){
char *zJournal;
char *zMasterPtr = 0;
/* Load the entire master journal file into space obtained from
** sqliteMalloc() and pointed to by zMasterJournal.
*/
zMasterJournal = (char *)sqliteMalloc(nMasterJournal);
if( !zMasterJournal ){
rc = SQLITE_NOMEM;
goto delmaster_out;
}
rc = sqlite3OsRead(master, zMasterJournal, nMasterJournal);
if( rc!=SQLITE_OK ) goto delmaster_out;
zJournal = zMasterJournal;
while( (zJournal-zMasterJournal)<nMasterJournal ){
if( sqlite3OsFileExists(zJournal) ){
/* One of the journals pointed to by the master journal exists.
** Open it and check if it points at the master journal. If
** so, return without deleting the master journal file.
*/
OsFile *journal = 0;
int c;
rc = sqlite3OsOpenReadOnly(zJournal, &journal);
assert( rc!=SQLITE_OK || journal );
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
rc = readMasterJournal(journal, &zMasterPtr);
sqlite3OsClose(&journal);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
c = zMasterPtr!=0 && strcmp(zMasterPtr, zMaster)==0;
sqliteFree(zMasterPtr);
if( c ){
/* We have a match. Do not delete the master journal file. */
goto delmaster_out;
}
}
zJournal += (strlen(zJournal)+1);
}
}
rc = sqlite3OsDelete(zMaster);
delmaster_out:
if( zMasterJournal ){
sqliteFree(zMasterJournal);
}
if( master_open ){
sqlite3OsClose(&master);
}
return rc;
}
static void pager_truncate_cache(Pager *pPager);
/*
** Truncate the main file of the given pager to the number of pages
** indicated. Also truncate the cached representation of the file.
*/
static int pager_truncate(Pager *pPager, int nPage){
int rc = SQLITE_OK;
if( pPager->state>=PAGER_EXCLUSIVE ){
rc = sqlite3OsTruncate(pPager->fd, pPager->pageSize*(i64)nPage);
}
if( rc==SQLITE_OK ){
pPager->dbSize = nPage;
pager_truncate_cache(pPager);
}
return rc;
}
/*
** Set the sectorSize for the given pager.
**
** The sector size is the larger of the sector size reported
** by sqlite3OsSectorSize() and the pageSize.
*/
static void setSectorSize(Pager *pPager){
pPager->sectorSize = sqlite3OsSectorSize(pPager->fd);
if( pPager->sectorSize<pPager->pageSize ){
pPager->sectorSize = pPager->pageSize;
}
}
/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.
**
** The journal file format is as follows:
**
** (1) 8 byte prefix. A copy of aJournalMagic[].
** (2) 4 byte big-endian integer which is the number of valid page records
** in the journal. If this value is 0xffffffff, then compute the
** number of page records from the journal size.
** (3) 4 byte big-endian integer which is the initial value for the
** sanity checksum.
** (4) 4 byte integer which is the number of pages to truncate the
** database to during a rollback.
** (5) 4 byte integer which is the number of bytes in the master journal
** name. The value may be zero (indicate that there is no master
** journal.)
** (6) N bytes of the master journal name. The name will be nul-terminated
** and might be shorter than the value read from (5). If the first byte
** of the name is \000 then there is no master journal. The master
** journal name is stored in UTF-8.
** (7) Zero or more pages instances, each as follows:
** + 4 byte page number.
** + pPager->pageSize bytes of data.
** + 4 byte checksum
**
** When we speak of the journal header, we mean the first 6 items above.
** Each entry in the journal is an instance of the 7th item.
**
** Call the value from the second bullet "nRec". nRec is the number of
** valid page entries in the journal. In most cases, you can compute the
** value of nRec from the size of the journal file. But if a power
** failure occurred while the journal was being written, it could be the
** case that the size of the journal file had already been increased but
** the extra entries had not yet made it safely to disk. In such a case,
** the value of nRec computed from the file size would be too large. For
** that reason, we always use the nRec value in the header.
**
** If the nRec value is 0xffffffff it means that nRec should be computed
** from the file size. This value is used when the user selects the
** no-sync option for the journal. A power failure could lead to corruption
** in this case. But for things like temporary table (which will be
** deleted when the power is restored) we don't care.
**
** If the file opened as the journal file is not a well-formed
** journal file then all pages up to the first corrupted page are rolled
** back (or no pages if the journal header is corrupted). The journal file
** is then deleted and SQLITE_OK returned, just as if no corruption had
** been encountered.
**
** If an I/O or malloc() error occurs, the journal-file is not deleted
** and an error code is returned.
*/
static int pager_playback(Pager *pPager, int isHot){
i64 szJ; /* Size of the journal file in bytes */
u32 nRec; /* Number of Records in the journal */
int i; /* Loop counter */
Pgno mxPg = 0; /* Size of the original file in pages */
int rc; /* Result code of a subroutine */
char *zMaster = 0; /* Name of master journal file if any */
/* Figure out how many records are in the journal. Abort early if
** the journal is empty.
*/
assert( pPager->journalOpen );
rc = sqlite3OsFileSize(pPager->jfd, &szJ);
if( rc!=SQLITE_OK || szJ==0 ){
goto end_playback;
}
/* Read the master journal name from the journal, if it is present.
** If a master journal file name is specified, but the file is not
** present on disk, then the journal is not hot and does not need to be
** played back.
*/
rc = readMasterJournal(pPager->jfd, &zMaster);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK || (zMaster && !sqlite3OsFileExists(zMaster)) ){
sqliteFree(zMaster);
zMaster = 0;
if( rc==SQLITE_DONE ) rc = SQLITE_OK;
goto end_playback;
}
sqlite3OsSeek(pPager->jfd, 0);
pPager->journalOff = 0;
/* This loop terminates either when the readJournalHdr() call returns
** SQLITE_DONE or an IO error occurs. */
while( 1 ){
/* Read the next journal header from the journal file. If there are
** not enough bytes left in the journal file for a complete header, or
** it is corrupted, then a process must of failed while writing it.
** This indicates nothing more needs to be rolled back.
*/
rc = readJournalHdr(pPager, szJ, &nRec, &mxPg);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
}
goto end_playback;
}
/* If nRec is 0xffffffff, then this journal was created by a process
** working in no-sync mode. This means that the rest of the journal
** file consists of pages, there are no more journal headers. Compute
** the value of nRec based on this assumption.
*/
if( nRec==0xffffffff ){
assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
nRec = (szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager);
}
/* If nRec is 0 and this rollback is of a transaction created by this
** process and if this is the final header in the journal, then it means
** that this part of the journal was being filled but has not yet been
** synced to disk. Compute the number of pages based on the remaining
** size of the file.
**
** The third term of the test was added to fix ticket #2565.
*/
if( nRec==0 && !isHot &&
pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
nRec = (szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager);
}
/* If this is the first header read from the journal, truncate the
** database file back to it's original size.
*/
if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
rc = pager_truncate(pPager, mxPg);
if( rc!=SQLITE_OK ){
goto end_playback;
}
}
/* Copy original pages out of the journal and back into the database file.
*/
for(i=0; i<nRec; i++){
rc = pager_playback_one_page(pPager, pPager->jfd, 1);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
pPager->journalOff = szJ;
break;
}else{
goto end_playback;
}
}
}
}
/*NOTREACHED*/
assert( 0 );
end_playback:
if( rc==SQLITE_OK ){
rc = pager_end_transaction(pPager);
}
if( zMaster ){
/* If there was a master journal and this routine will return success,
** see if it is possible to delete the master journal.
*/
if( rc==SQLITE_OK ){
rc = pager_delmaster(zMaster);
}
sqliteFree(zMaster);
}
/* The Pager.sectorSize variable may have been updated while rolling
** back a journal created by a process with a different sector size
** value. Reset it to the correct value for this process.
*/
setSectorSize(pPager);
return rc;
}
/*
** Playback the statement journal.
**
** This is similar to playing back the transaction journal but with
** a few extra twists.
**
** (1) The number of pages in the database file at the start of
** the statement is stored in pPager->stmtSize, not in the
** journal file itself.
**
** (2) In addition to playing back the statement journal, also
** playback all pages of the transaction journal beginning
** at offset pPager->stmtJSize.
*/
static int pager_stmt_playback(Pager *pPager){
i64 szJ; /* Size of the full journal */
i64 hdrOff;
int nRec; /* Number of Records */
int i; /* Loop counter */
int rc;
szJ = pPager->journalOff;
#ifndef NDEBUG
{
i64 os_szJ;
rc = sqlite3OsFileSize(pPager->jfd, &os_szJ);
if( rc!=SQLITE_OK ) return rc;
assert( szJ==os_szJ );
}
#endif
/* Set hdrOff to be the offset just after the end of the last journal
** page written before the first journal-header for this statement
** transaction was written, or the end of the file if no journal
** header was written.
*/
hdrOff = pPager->stmtHdrOff;
assert( pPager->fullSync || !hdrOff );
if( !hdrOff ){
hdrOff = szJ;
}
/* Truncate the database back to its original size.
*/
rc = pager_truncate(pPager, pPager->stmtSize);
assert( pPager->state>=PAGER_SHARED );
/* Figure out how many records are in the statement journal.
*/
assert( pPager->stmtInUse && pPager->journalOpen );
sqlite3OsSeek(pPager->stfd, 0);
nRec = pPager->stmtNRec;
/* Copy original pages out of the statement journal and back into the
** database file. Note that the statement journal omits checksums from
** each record since power-failure recovery is not important to statement
** journals.
*/
for(i=nRec-1; i>=0; i--){
rc = pager_playback_one_page(pPager, pPager->stfd, 0);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK ) goto end_stmt_playback;
}
/* Now roll some pages back from the transaction journal. Pager.stmtJSize
** was the size of the journal file when this statement was started, so
** everything after that needs to be rolled back, either into the
** database, the memory cache, or both.
**
** If it is not zero, then Pager.stmtHdrOff is the offset to the start
** of the first journal header written during this statement transaction.
*/
rc = sqlite3OsSeek(pPager->jfd, pPager->stmtJSize);
if( rc!=SQLITE_OK ){
goto end_stmt_playback;
}
pPager->journalOff = pPager->stmtJSize;
pPager->cksumInit = pPager->stmtCksum;
while( pPager->journalOff < hdrOff ){
rc = pager_playback_one_page(pPager, pPager->jfd, 1);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK ) goto end_stmt_playback;
}
while( pPager->journalOff < szJ ){
u32 nJRec; /* Number of Journal Records */
u32 dummy;
rc = readJournalHdr(pPager, szJ, &nJRec, &dummy);
if( rc!=SQLITE_OK ){
assert( rc!=SQLITE_DONE );
goto end_stmt_playback;
}
if( nJRec==0 ){
nJRec = (szJ - pPager->journalOff) / (pPager->pageSize+8);
}
for(i=nJRec-1; i>=0 && pPager->journalOff < szJ; i--){
rc = pager_playback_one_page(pPager, pPager->jfd, 1);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK ) goto end_stmt_playback;
}
}
pPager->journalOff = szJ;
end_stmt_playback:
if( rc==SQLITE_OK) {
pPager->journalOff = szJ;
/* pager_reload_cache(pPager); */
}
return rc;
}
/*
** Change the maximum number of in-memory pages that are allowed.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
if( mxPage>10 ){
pPager->mxPage = mxPage;
}else{
pPager->mxPage = 10;
}
}
/*
** Adjust the robustness of the database to damage due to OS crashes
** or power failures by changing the number of syncs()s when writing
** the rollback journal. There are three levels:
**
** OFF sqlite3OsSync() is never called. This is the default
** for temporary and transient files.
**
** NORMAL The journal is synced once before writes begin on the
** database. This is normally adequate protection, but
** it is theoretically possible, though very unlikely,
** that an inopertune power failure could leave the journal
** in a state which would cause damage to the database
** when it is rolled back.
**
** FULL The journal is synced twice before writes begin on the
** database (with some additional information - the nRec field
** of the journal header - being written in between the two
** syncs). If we assume that writing a
** single disk sector is atomic, then this mode provides
** assurance that the journal will not be corrupted to the
** point of causing damage to the database during rollback.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
void sqlite3PagerSetSafetyLevel(Pager *pPager, int level, int full_fsync){
pPager->noSync = level==1 || pPager->tempFile;
pPager->fullSync = level==3 && !pPager->tempFile;
pPager->full_fsync = full_fsync;
if( pPager->noSync ) pPager->needSync = 0;
}
#endif
/*
** The following global variable is incremented whenever the library
** attempts to open a temporary file. This information is used for
** testing and analysis only.
*/
#ifdef SQLITE_TEST
int sqlite3_opentemp_count = 0;
#endif
/*
** Open a temporary file.
**
** Write the file descriptor into *fd. Return SQLITE_OK on success or some
** other error code if we fail.
**
** The OS will automatically delete the temporary file when it is
** closed.
*/
static int sqlite3PagerOpentemp(OsFile **pFd){
int cnt = 8;
int rc;
char zFile[SQLITE_TEMPNAME_SIZE];
#ifdef SQLITE_TEST
sqlite3_opentemp_count++; /* Used for testing and analysis only */
#endif
do{
cnt--;
sqlite3OsTempFileName(zFile);
rc = sqlite3OsOpenExclusive(zFile, pFd, 1);
assert( rc!=SQLITE_OK || *pFd );
}while( cnt>0 && rc!=SQLITE_OK && rc!=SQLITE_NOMEM );
return rc;
}
/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist. The file is not locked until
** the first call to sqlite3PagerGet() and is only held open until the
** last page is released using sqlite3PagerUnref().
**
** If zFilename is NULL then a randomly-named temporary file is created
** and used as the file to be cached. The file will be deleted
** automatically when it is closed.
**
** If zFilename is ":memory:" then all information is held in cache.
** It is never written to disk. This can be used to implement an
** in-memory database.
*/
int sqlite3PagerOpen(
Pager **ppPager, /* Return the Pager structure here */
const char *zFilename, /* Name of the database file to open */
int nExtra, /* Extra bytes append to each in-memory page */
int flags /* flags controlling this file */
){
Pager *pPager = 0;
char *zFullPathname = 0;
int nameLen; /* Compiler is wrong. This is always initialized before use */
OsFile *fd = 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;
char zTemp[SQLITE_TEMPNAME_SIZE];
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/* A malloc() cannot fail in sqlite3ThreadData() as one or more calls to
** malloc() must have already been made by this thread before it gets
** to this point. This means the ThreadData must have been allocated already
** so that ThreadData.nAlloc can be set. It would be nice to assert
** that ThreadData.nAlloc is non-zero, but alas this breaks test cases
** written to invoke the pager directly.
*/
ThreadData *pTsd = sqlite3ThreadData();
assert( pTsd );
#endif
/* We used to test if malloc() had already failed before proceeding.
** But the way this function is used in SQLite means that can never
** happen. Furthermore, if the malloc-failed flag is already set,
** either the call to sqliteStrDup() or sqliteMalloc() below will
** fail shortly and SQLITE_NOMEM returned anyway.
*/
*ppPager = 0;
/* Open the pager file and set zFullPathname to point at malloc()ed
** memory containing the complete filename (i.e. including the directory).
*/
if( zFilename && zFilename[0] ){
#ifndef SQLITE_OMIT_MEMORYDB
if( strcmp(zFilename,":memory:")==0 ){
memDb = 1;
zFullPathname = sqliteStrDup("");
}else
#endif
{
zFullPathname = sqlite3OsFullPathname(zFilename);
if( zFullPathname ){
rc = sqlite3OsOpenReadWrite(zFullPathname, &fd, &readOnly);
assert( rc!=SQLITE_OK || fd );
}
}
}else{
rc = sqlite3PagerOpentemp(&fd);
sqlite3OsTempFileName(zTemp);
zFilename = zTemp;
zFullPathname = sqlite3OsFullPathname(zFilename);
if( rc==SQLITE_OK ){
tempFile = 1;
}
}
/* Allocate the Pager structure. As part of the same allocation, allocate
** space for the full paths of the file, directory and journal
** (Pager.zFilename, Pager.zDirectory and Pager.zJournal).
*/
if( zFullPathname ){
nameLen = strlen(zFullPathname);
pPager = sqliteMalloc( sizeof(*pPager) + nameLen*3 + 30 );
if( pPager && rc==SQLITE_OK ){
pPager->pTmpSpace = (char *)sqliteMallocRaw(SQLITE_DEFAULT_PAGE_SIZE);
}
}
/* If an error occured in either of the blocks above, free the memory
** pointed to by zFullPathname, free the Pager structure and close the
** file. Since the pager is not allocated there is no need to set
** any Pager.errMask variables.
*/
if( !pPager || !zFullPathname || !pPager->pTmpSpace || rc!=SQLITE_OK ){
sqlite3OsClose(&fd);
sqliteFree(zFullPathname);
sqliteFree(pPager);
return ((rc==SQLITE_OK)?SQLITE_NOMEM:rc);
}
PAGERTRACE3("OPEN %d %s\n", FILEHANDLEID(fd), zFullPathname);
IOTRACE(("OPEN %p %s\n", pPager, zFullPathname))
pPager->zFilename = (char*)&pPager[1];
pPager->zDirectory = &pPager->zFilename[nameLen+1];
pPager->zJournal = &pPager->zDirectory[nameLen+1];
memcpy(pPager->zFilename, zFullPathname, nameLen+1);
memcpy(pPager->zDirectory, zFullPathname, nameLen+1);
for(i=nameLen; i>0 && pPager->zDirectory[i-1]!='/'; i--){}
if( i>0 ) pPager->zDirectory[i-1] = 0;
memcpy(pPager->zJournal, zFullPathname,nameLen);
sqliteFree(zFullPathname);
memcpy(&pPager->zJournal[nameLen], "-journal",sizeof("-journal"));
pPager->fd = fd;
/* pPager->journalOpen = 0; */
pPager->useJournal = useJournal && !memDb;
pPager->noReadlock = noReadlock && readOnly;
/* pPager->stmtOpen = 0; */
/* pPager->stmtInUse = 0; */
/* pPager->nRef = 0; */
pPager->dbSize = memDb-1;
pPager->pageSize = SQLITE_DEFAULT_PAGE_SIZE;
/* pPager->stmtSize = 0; */
/* pPager->stmtJSize = 0; */
/* pPager->nPage = 0; */
pPager->mxPage = 100;
pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
assert( PAGER_UNLOCK==0 );
/* pPager->state = PAGER_UNLOCK; */
/* pPager->errMask = 0; */
pPager->tempFile = tempFile;
assert( tempFile==PAGER_LOCKINGMODE_NORMAL
|| tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
pPager->exclusiveMode = tempFile;
pPager->memDb = memDb;
pPager->readOnly = readOnly;
/* pPager->needSync = 0; */
pPager->noSync = pPager->tempFile || !useJournal;
pPager->fullSync = (pPager->noSync?0:1);
/* pPager->pFirst = 0; */
/* pPager->pFirstSynced = 0; */
/* pPager->pLast = 0; */
pPager->nExtra = FORCE_ALIGNMENT(nExtra);
assert(fd||memDb);
if( !memDb ){
setSectorSize(pPager);
}
/* pPager->pBusyHandler = 0; */
/* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
*ppPager = pPager;
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
pPager->pNext = pTsd->pPager;
pTsd->pPager = pPager;
#endif
return SQLITE_OK;
}
/*
** Set the busy handler function.
*/
void sqlite3PagerSetBusyhandler(Pager *pPager, BusyHandler *pBusyHandler){
pPager->pBusyHandler = pBusyHandler;
}
/*
** Set the destructor for this pager. If not NULL, the destructor is called
** when the reference count on each page reaches zero. The destructor can
** be used to clean up information in the extra segment appended to each page.
**
** The destructor is not called as a result sqlite3PagerClose().
** Destructors are only called by sqlite3PagerUnref().
*/
void sqlite3PagerSetDestructor(Pager *pPager, void (*xDesc)(DbPage*,int)){
pPager->xDestructor = xDesc;
}
/*
** Set the reinitializer for this pager. If not NULL, the reinitializer
** is called when the content of a page in cache is restored to its original
** value as a result of a rollback. The callback gives higher-level code
** an opportunity to restore the EXTRA section to agree with the restored
** page data.
*/
void sqlite3PagerSetReiniter(Pager *pPager, void (*xReinit)(DbPage*,int)){
pPager->xReiniter = xReinit;
}
/*
** Set the page size. Return the new size. If the suggest new page
** size is inappropriate, then an alternative page size is selected
** and returned.
*/
int sqlite3PagerSetPagesize(Pager *pPager, int pageSize){
assert( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE );
if( !pPager->memDb && pPager->nRef==0 ){
pager_reset(pPager);
pPager->pageSize = pageSize;
pPager->pTmpSpace = sqlite3ReallocOrFree(pPager->pTmpSpace, pageSize);
}
return pPager->pageSize;
}
/*
** Attempt to set the maximum database page count if mxPage is positive.
** Make no changes if mxPage is zero or negative. And never reduce the
** maximum page count below the current size of the database.
**
** Regardless of mxPage, return the current maximum page count.
*/
int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
if( mxPage>0 ){
pPager->mxPgno = mxPage;
}
sqlite3PagerPagecount(pPager);
return pPager->mxPgno;
}
/*
** The following set of routines are used to disable the simulated
** I/O error mechanism. These routines are used to avoid simulated
** errors in places where we do not care about errors.
**
** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
** and generate no code.
*/
#ifdef SQLITE_TEST
extern int sqlite3_io_error_pending;
extern int sqlite3_io_error_hit;
static int saved_cnt;
void disable_simulated_io_errors(void){
saved_cnt = sqlite3_io_error_pending;
sqlite3_io_error_pending = -1;
}
void enable_simulated_io_errors(void){
sqlite3_io_error_pending = saved_cnt;
}
#else
# define disable_simulated_io_errors()
# define enable_simulated_io_errors()
#endif
/*
** Read the first N bytes from the beginning of the file into memory
** that pDest points to.
**
** No error checking is done. The rational for this is that this function
** may be called even if the file does not exist or contain a header. In
** these cases sqlite3OsRead() will return an error, to which the correct
** response is to zero the memory at pDest and continue. A real IO error
** will presumably recur and be picked up later (Todo: Think about this).
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
int rc = SQLITE_OK;
memset(pDest, 0, N);
if( MEMDB==0 ){
disable_simulated_io_errors();
sqlite3OsSeek(pPager->fd, 0);
enable_simulated_io_errors();
IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
rc = sqlite3OsRead(pPager->fd, pDest, N);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
}
return rc;
}
/*
** Return the total number of pages in the disk file associated with
** pPager.
**
** If the PENDING_BYTE lies on the page directly after the end of the
** file, then consider this page part of the file too. For example, if
** PENDING_BYTE is byte 4096 (the first byte of page 5) and the size of the
** file is 4096 bytes, 5 is returned instead of 4.
*/
int sqlite3PagerPagecount(Pager *pPager){
i64 n;
int rc;
assert( pPager!=0 );
if( pPager->errCode ){
return 0;
}
if( pPager->dbSize>=0 ){
n = pPager->dbSize;
} else {
if( (rc = sqlite3OsFileSize(pPager->fd, &n))!=SQLITE_OK ){
pager_error(pPager, rc);
return 0;
}
if( n>0 && n<pPager->pageSize ){
n = 1;
}else{
n /= pPager->pageSize;
}
if( pPager->state!=PAGER_UNLOCK ){
pPager->dbSize = n;
}
}
if( n==(PENDING_BYTE/pPager->pageSize) ){
n++;
}
if( n>pPager->mxPgno ){
pPager->mxPgno = n;
}
return n;
}
#ifndef SQLITE_OMIT_MEMORYDB
/*
** Clear a PgHistory block
*/
static void clearHistory(PgHistory *pHist){
sqliteFree(pHist->pOrig);
sqliteFree(pHist->pStmt);
pHist->pOrig = 0;
pHist->pStmt = 0;
}
#else
#define clearHistory(x)
#endif
/*
** Forward declaration
*/
static int syncJournal(Pager*);
/*
** Unlink pPg from it's hash chain. Also set the page number to 0 to indicate
** that the page is not part of any hash chain. This is required because the
** sqlite3PagerMovepage() routine can leave a page in the
** pNextFree/pPrevFree list that is not a part of any hash-chain.
*/
static void unlinkHashChain(Pager *pPager, PgHdr *pPg){
if( pPg->pgno==0 ){
assert( pPg->pNextHash==0 && pPg->pPrevHash==0 );
return;
}
if( pPg->pNextHash ){
pPg->pNextHash->pPrevHash = pPg->pPrevHash;
}
if( pPg->pPrevHash ){
assert( pPager->aHash[pPg->pgno & (pPager->nHash-1)]!=pPg );
pPg->pPrevHash->pNextHash = pPg->pNextHash;
}else{
int h = pPg->pgno & (pPager->nHash-1);
pPager->aHash[h] = pPg->pNextHash;
}
if( MEMDB ){
clearHistory(PGHDR_TO_HIST(pPg, pPager));
}
pPg->pgno = 0;
pPg->pNextHash = pPg->pPrevHash = 0;
}
/*
** Unlink a page from the free list (the list of all pages where nRef==0)
** and from its hash collision chain.
*/
static void unlinkPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
/* Keep the pFirstSynced pointer pointing at the first synchronized page */
if( pPg==pPager->pFirstSynced ){
PgHdr *p = pPg->pNextFree;
while( p && p->needSync ){ p = p->pNextFree; }
pPager->pFirstSynced = p;
}
/* Unlink from the freelist */
if( pPg->pPrevFree ){
pPg->pPrevFree->pNextFree = pPg->pNextFree;
}else{
assert( pPager->pFirst==pPg );
pPager->pFirst = pPg->pNextFree;
}
if( pPg->pNextFree ){
pPg->pNextFree->pPrevFree = pPg->pPrevFree;
}else{
assert( pPager->pLast==pPg );
pPager->pLast = pPg->pPrevFree;
}
pPg->pNextFree = pPg->pPrevFree = 0;
/* Unlink from the pgno hash table */
unlinkHashChain(pPager, pPg);
}
/*
** This routine is used to truncate the cache when a database
** is truncated. Drop from the cache all pages whose pgno is
** larger than pPager->dbSize and is unreferenced.
**
** Referenced pages larger than pPager->dbSize are zeroed.
**
** Actually, at the point this routine is called, it would be
** an error to have a referenced page. But rather than delete
** that page and guarantee a subsequent segfault, it seems better
** to zero it and hope that we error out sanely.
*/
static void pager_truncate_cache(Pager *pPager){
PgHdr *pPg;
PgHdr **ppPg;
int dbSize = pPager->dbSize;
ppPg = &pPager->pAll;
while( (pPg = *ppPg)!=0 ){
if( pPg->pgno<=dbSize ){
ppPg = &pPg->pNextAll;
}else if( pPg->nRef>0 ){
memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
ppPg = &pPg->pNextAll;
}else{
*ppPg = pPg->pNextAll;
IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
PAGER_INCR(sqlite3_pager_pgfree_count);
unlinkPage(pPg);
makeClean(pPg);
sqliteFree(pPg);
pPager->nPage--;
}
}
}
/*
** Try to obtain a lock on a file. Invoke the busy callback if the lock
** is currently not available. Repeat until the busy callback returns
** false or until the lock succeeds.
**
** Return SQLITE_OK on success and an error code if we cannot obtain
** the lock.
*/
static int pager_wait_on_lock(Pager *pPager, int locktype){
int rc;
/* The OS lock values must be the same as the Pager lock values */
assert( PAGER_SHARED==SHARED_LOCK );
assert( PAGER_RESERVED==RESERVED_LOCK );
assert( PAGER_EXCLUSIVE==EXCLUSIVE_LOCK );
/* If the file is currently unlocked then the size must be unknown */
assert( pPager->state>=PAGER_SHARED || pPager->dbSize<0 || MEMDB );
if( pPager->state>=locktype ){
rc = SQLITE_OK;
}else{
do {
rc = sqlite3OsLock(pPager->fd, locktype);
}while( rc==SQLITE_BUSY && sqlite3InvokeBusyHandler(pPager->pBusyHandler) );
if( rc==SQLITE_OK ){
pPager->state = locktype;
IOTRACE(("LOCK %p %d\n", pPager, locktype))
}
}
return rc;
}
/*
** Truncate the file to the number of pages specified.
*/
int sqlite3PagerTruncate(Pager *pPager, Pgno nPage){
int rc;
assert( pPager->state>=PAGER_SHARED || MEMDB );
sqlite3PagerPagecount(pPager);
if( pPager->errCode ){
rc = pPager->errCode;
return rc;
}
if( nPage>=(unsigned)pPager->dbSize ){
return SQLITE_OK;
}
if( MEMDB ){
pPager->dbSize = nPage;
pager_truncate_cache(pPager);
return SQLITE_OK;
}
rc = syncJournal(pPager);
if( rc!=SQLITE_OK ){
return rc;
}
/* Get an exclusive lock on the database before truncating. */
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
return rc;
}
rc = pager_truncate(pPager, nPage);
return rc;
}
/*
** Shutdown the page cache. Free all memory and close all files.
**
** If a transaction was in progress when this routine is called, that
** transaction is rolled back. All outstanding pages are invalidated
** and their memory is freed. Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
**
** This function always succeeds. If a transaction is active an attempt
** is made to roll it back. If an error occurs during the rollback
** a hot journal may be left in the filesystem but no error is returned
** to the caller.
*/
int sqlite3PagerClose(Pager *pPager){
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/* A malloc() cannot fail in sqlite3ThreadData() as one or more calls to
** malloc() must have already been made by this thread before it gets
** to this point. This means the ThreadData must have been allocated already
** so that ThreadData.nAlloc can be set.
*/
ThreadData *pTsd = sqlite3ThreadData();
assert( pPager );
assert( pTsd && pTsd->nAlloc );
#endif
disable_simulated_io_errors();
pPager->errCode = 0;
pPager->exclusiveMode = 0;
pager_reset(pPager);
pagerUnlockAndRollback(pPager);
enable_simulated_io_errors();
PAGERTRACE2("CLOSE %d\n", PAGERID(pPager));
IOTRACE(("CLOSE %p\n", pPager))
assert( pPager->errCode || (pPager->journalOpen==0 && pPager->stmtOpen==0) );
if( pPager->journalOpen ){
sqlite3OsClose(&pPager->jfd);
}
sqliteFree(pPager->aInJournal);
if( pPager->stmtOpen ){
sqlite3OsClose(&pPager->stfd);
}
sqlite3OsClose(&pPager->fd);
/* Temp files are automatically deleted by the OS
** if( pPager->tempFile ){
** sqlite3OsDelete(pPager->zFilename);
** }
*/
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/* Remove the pager from the linked list of pagers starting at
** ThreadData.pPager if memory-management is enabled.
*/
if( pPager==pTsd->pPager ){
pTsd->pPager = pPager->pNext;
}else{
Pager *pTmp;
for(pTmp = pTsd->pPager; pTmp->pNext!=pPager; pTmp=pTmp->pNext){}
pTmp->pNext = pPager->pNext;
}
#endif
sqliteFree(pPager->aHash);
sqliteFree(pPager->pTmpSpace);
sqliteFree(pPager);
return SQLITE_OK;
}
#if !defined(NDEBUG) || defined(SQLITE_TEST)
/*
** Return the page number for the given page data.
*/
Pgno sqlite3PagerPagenumber(DbPage *p){
return p->pgno;
}
#endif
/*
** The page_ref() function increments the reference count for a page.
** If the page is currently on the freelist (the reference count is zero) then
** remove it from the freelist.
**
** For non-test systems, page_ref() is a macro that calls _page_ref()
** online of the reference count is zero. For test systems, page_ref()
** is a real function so that we can set breakpoints and trace it.
*/
static void _page_ref(PgHdr *pPg){
if( pPg->nRef==0 ){
/* The page is currently on the freelist. Remove it. */
if( pPg==pPg->pPager->pFirstSynced ){
PgHdr *p = pPg->pNextFree;
while( p && p->needSync ){ p = p->pNextFree; }
pPg->pPager->pFirstSynced = p;
}
if( pPg->pPrevFree ){
pPg->pPrevFree->pNextFree = pPg->pNextFree;
}else{
pPg->pPager->pFirst = pPg->pNextFree;
}
if( pPg->pNextFree ){
pPg->pNextFree->pPrevFree = pPg->pPrevFree;
}else{
pPg->pPager->pLast = pPg->pPrevFree;
}
pPg->pPager->nRef++;
}
pPg->nRef++;
REFINFO(pPg);
}
#ifdef SQLITE_DEBUG
static void page_ref(PgHdr *pPg){
if( pPg->nRef==0 ){
_page_ref(pPg);
}else{
pPg->nRef++;
REFINFO(pPg);
}
}
#else
# define page_ref(P) ((P)->nRef==0?_page_ref(P):(void)(P)->nRef++)
#endif
/*
** Increment the reference count for a page. The input pointer is
** a reference to the page data.
*/
int sqlite3PagerRef(DbPage *pPg){
page_ref(pPg);
return SQLITE_OK;
}
/*
** Sync the journal. In other words, make sure all the pages that have
** been written to the journal have actually reached the surface of the
** disk. It is not safe to modify the original database file until after
** the journal has been synced. If the original database is modified before
** the journal is synced and a power failure occurs, the unsynced journal
** data would be lost and we would be unable to completely rollback the
** database changes. Database corruption would occur.
**
** This routine also updates the nRec field in the header of the journal.
** (See comments on the pager_playback() routine for additional information.)
** If the sync mode is FULL, two syncs will occur. First the whole journal
** is synced, then the nRec field is updated, then a second sync occurs.
**
** For temporary databases, we do not care if we are able to rollback
** after a power failure, so sync occurs.
**
** This routine clears the needSync field of every page current held in
** memory.
*/
static int syncJournal(Pager *pPager){
PgHdr *pPg;
int rc = SQLITE_OK;
/* Sync the journal before modifying the main database
** (assuming there is a journal and it needs to be synced.)
*/
if( pPager->needSync ){
if( !pPager->tempFile ){
assert( pPager->journalOpen );
/* assert( !pPager->noSync ); // noSync might be set if synchronous
** was turned off after the transaction was started. Ticket #615 */
#ifndef NDEBUG
{
/* Make sure the pPager->nRec counter we are keeping agrees
** with the nRec computed from the size of the journal file.
*/
i64 jSz;
rc = sqlite3OsFileSize(pPager->jfd, &jSz);
if( rc!=0 ) return rc;
assert( pPager->journalOff==jSz );
}
#endif
{
/* Write the nRec value into the journal file header. If in
** full-synchronous mode, sync the journal first. This ensures that
** all data has really hit the disk before nRec is updated to mark
** it as a candidate for rollback.
*/
if( pPager->fullSync ){
PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, 0);
if( rc!=0 ) return rc;
}
rc = sqlite3OsSeek(pPager->jfd,
pPager->journalHdr + sizeof(aJournalMagic));
if( rc ) return rc;
IOTRACE(("JHDR %p %lld %d\n", pPager,
pPager->journalHdr + sizeof(aJournalMagic), 4))
rc = write32bits(pPager->jfd, pPager->nRec);
if( rc ) return rc;
rc = sqlite3OsSeek(pPager->jfd, pPager->journalOff);
if( rc ) return rc;
}
PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->full_fsync);
if( rc!=0 ) return rc;
pPager->journalStarted = 1;
}
pPager->needSync = 0;
/* Erase the needSync flag from every page.
*/
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
pPg->needSync = 0;
}
pPager->pFirstSynced = pPager->pFirst;
}
#ifndef NDEBUG
/* If the Pager.needSync flag is clear then the PgHdr.needSync
** flag must also be clear for all pages. Verify that this
** invariant is true.
*/
else{
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
assert( pPg->needSync==0 );
}
assert( pPager->pFirstSynced==pPager->pFirst );
}
#endif
return rc;
}
/*
** Merge two lists of pages connected by pDirty and in pgno order.
** Do not both fixing the pPrevDirty pointers.
*/
static PgHdr *merge_pagelist(PgHdr *pA, PgHdr *pB){
PgHdr result, *pTail;
pTail = &result;
while( pA && pB ){
if( pA->pgno<pB->pgno ){
pTail->pDirty = pA;
pTail = pA;
pA = pA->pDirty;
}else{
pTail->pDirty = pB;
pTail = pB;
pB = pB->pDirty;
}
}
if( pA ){
pTail->pDirty = pA;
}else if( pB ){
pTail->pDirty = pB;
}else{
pTail->pDirty = 0;
}
return result.pDirty;
}
/*
** Sort the list of pages in accending order by pgno. Pages are
** connected by pDirty pointers. The pPrevDirty pointers are
** corrupted by this sort.
*/
#define N_SORT_BUCKET_ALLOC 25
#define N_SORT_BUCKET 25
#ifdef SQLITE_TEST
int sqlite3_pager_n_sort_bucket = 0;
#undef N_SORT_BUCKET
#define N_SORT_BUCKET \
(sqlite3_pager_n_sort_bucket?sqlite3_pager_n_sort_bucket:N_SORT_BUCKET_ALLOC)
#endif
static PgHdr *sort_pagelist(PgHdr *pIn){
PgHdr *a[N_SORT_BUCKET_ALLOC], *p;
int i;
memset(a, 0, sizeof(a));
while( pIn ){
p = pIn;
pIn = p->pDirty;
p->pDirty = 0;
for(i=0; i<N_SORT_BUCKET-1; i++){
if( a[i]==0 ){
a[i] = p;
break;
}else{
p = merge_pagelist(a[i], p);
a[i] = 0;
}
}
if( i==N_SORT_BUCKET-1 ){
/* Coverage: To get here, there need to be 2^(N_SORT_BUCKET)
** elements in the input list. This is possible, but impractical.
** Testing this line is the point of global variable
** sqlite3_pager_n_sort_bucket.
*/
a[i] = merge_pagelist(a[i], p);
}
}
p = a[0];
for(i=1; i<N_SORT_BUCKET; i++){
p = merge_pagelist(p, a[i]);
}
return p;
}
/*
** Given a list of pages (connected by the PgHdr.pDirty pointer) write
** every one of those pages out to the database file and mark them all
** as clean.
*/
static int pager_write_pagelist(PgHdr *pList){
Pager *pPager;
int rc;
if( pList==0 ) return SQLITE_OK;
pPager = pList->pPager;
/* At this point there may be either a RESERVED or EXCLUSIVE lock on the
** database file. If there is already an EXCLUSIVE lock, the following
** calls to sqlite3OsLock() are no-ops.
**
** Moving the lock from RESERVED to EXCLUSIVE actually involves going
** through an intermediate state PENDING. A PENDING lock prevents new
** readers from attaching to the database but is unsufficient for us to
** write. The idea of a PENDING lock is to prevent new readers from
** coming in while we wait for existing readers to clear.
**
** While the pager is in the RESERVED state, the original database file
** is unchanged and we can rollback without having to playback the
** journal into the original database file. Once we transition to
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
return rc;
}
pList = sort_pagelist(pList);
while( pList ){
assert( pList->dirty );
rc = sqlite3OsSeek(pPager->fd, (pList->pgno-1)*(i64)pPager->pageSize);
if( rc ) return rc;
/* If there are dirty pages in the page cache with page numbers greater
** than Pager.dbSize, this means sqlite3PagerTruncate() was called to
** make the file smaller (presumably by auto-vacuum code). Do not write
** any such pages to the file.
*/
if( pList->pgno<=pPager->dbSize ){
char *pData = CODEC2(pPager, PGHDR_TO_DATA(pList), pList->pgno, 6);
PAGERTRACE4("STORE %d page %d hash(%08x)\n",
PAGERID(pPager), pList->pgno, pager_pagehash(pList));
IOTRACE(("PGOUT %p %d\n", pPager, pList->pgno));
rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize);
PAGER_INCR(sqlite3_pager_writedb_count);
PAGER_INCR(pPager->nWrite);
if( pList->pgno==1 ){
memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
}
}
#ifndef NDEBUG
else{
PAGERTRACE3("NOSTORE %d page %d\n", PAGERID(pPager), pList->pgno);
}
#endif
if( rc ) return rc;
pList->dirty = 0;
#ifdef SQLITE_CHECK_PAGES
pList->pageHash = pager_pagehash(pList);
#endif
pList = pList->pDirty;
}
return SQLITE_OK;
}
/*
** Collect every dirty page into a dirty list and
** return a pointer to the head of that list. All pages are
** collected even if they are still in use.
*/
static PgHdr *pager_get_all_dirty_pages(Pager *pPager){
return pPager->pDirty;
}
/*
** Return TRUE if there is a hot journal on the given pager.
** A hot journal is one that needs to be played back.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
** database with the same name. Just delete the journal.
*/
static int hasHotJournal(Pager *pPager){
if( !pPager->useJournal ) return 0;
if( !sqlite3OsFileExists(pPager->zJournal) ){
return 0;
}
if( sqlite3OsCheckReservedLock(pPager->fd) ){
return 0;
}
if( sqlite3PagerPagecount(pPager)==0 ){
sqlite3OsDelete(pPager->zJournal);
return 0;
}else{
return 1;
}
}
/*
** Try to find a page in the cache that can be recycled.
**
** This routine may return SQLITE_IOERR, SQLITE_FULL or SQLITE_OK. It
** does not set the pPager->errCode variable.
*/
static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
PgHdr *pPg;
*ppPg = 0;
assert(!MEMDB);
/* Find a page to recycle. Try to locate a page that does not
** require us to do an fsync() on the journal.
*/
pPg = pPager->pFirstSynced;
/* If we could not find a page that does not require an fsync()
** on the journal file then fsync the journal file. This is a
** very slow operation, so we work hard to avoid it. But sometimes
** it can't be helped.
*/
if( pPg==0 && pPager->pFirst && syncOk && !MEMDB){
int rc = syncJournal(pPager);
if( rc!=0 ){
return rc;
}
if( pPager->fullSync ){
/* If in full-sync mode, write a new journal header into the
** journal file. This is done to avoid ever modifying a journal
** header that is involved in the rollback of pages that have
** already been written to the database (in case the header is
** trashed when the nRec field is updated).
*/
pPager->nRec = 0;
assert( pPager->journalOff > 0 );
assert( pPager->doNotSync==0 );
rc = writeJournalHdr(pPager);
if( rc!=0 ){
return rc;
}
}
pPg = pPager->pFirst;
}
if( pPg==0 ){
return SQLITE_OK;
}
assert( pPg->nRef==0 );
/* Write the page to the database file if it is dirty.
*/
if( pPg->dirty ){
int rc;
assert( pPg->needSync==0 );
makeClean(pPg);
pPg->dirty = 1;
pPg->pDirty = 0;
rc = pager_write_pagelist( pPg );
if( rc!=SQLITE_OK ){
return rc;
}
}
assert( pPg->dirty==0 );
/* If the page we are recycling is marked as alwaysRollback, then
** set the global alwaysRollback flag, thus disabling the
** sqlite3PagerDontRollback() optimization for the rest of this transaction.
** It is necessary to do this because the page marked alwaysRollback
** might be reloaded at a later time but at that point we won't remember
** that is was marked alwaysRollback. This means that all pages must
** be marked as alwaysRollback from here on out.
*/
if( pPg->alwaysRollback ){
IOTRACE(("ALWAYS_ROLLBACK %p\n", pPager))
pPager->alwaysRollback = 1;
}
/* Unlink the old page from the free list and the hash table
*/
unlinkPage(pPg);
assert( pPg->pgno==0 );
*ppPg = pPg;
return SQLITE_OK;
}
/*
** This function is called to free superfluous dynamically allocated memory
** held by the pager system. Memory in use by any SQLite pager allocated
** by the current thread may be sqliteFree()ed.
**
** nReq is the number of bytes of memory required. Once this much has
** been released, the function returns. A negative value for nReq means
** free as much memory as possible. The return value is the total number
** of bytes of memory released.
*/
#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
int sqlite3PagerReleaseMemory(int nReq){
const ThreadData *pTsdro = sqlite3ThreadDataReadOnly();
int nReleased = 0;
int i;
/* If the the global mutex is held, this subroutine becomes a
** o-op; zero bytes of memory are freed. This is because
** some of the code invoked by this function may also
** try to obtain the mutex, resulting in a deadlock.
*/
if( sqlite3OsInMutex(0) ){
return 0;
}
/* Outermost loop runs for at most two iterations. First iteration we
** try to find memory that can be released without calling fsync(). Second
** iteration (which only runs if the first failed to free nReq bytes of
** memory) is permitted to call fsync(). This is of course much more
** expensive.
*/
for(i=0; i<=1; i++){
/* Loop through all the SQLite pagers opened by the current thread. */
Pager *pPager = pTsdro->pPager;
for( ; pPager && (nReq<0 || nReleased<nReq); pPager=pPager->pNext){
PgHdr *pPg;
int rc;
if( MEMDB ){
continue;
}
/* For each pager, try to free as many pages as possible (without
** calling fsync() if this is the first iteration of the outermost
** loop).
*/
while( SQLITE_OK==(rc = pager_recycle(pPager, i, &pPg)) && pPg) {
/* We've found a page to free. At this point the page has been
** removed from the page hash-table, free-list and synced-list
** (pFirstSynced). It is still in the all pages (pAll) list.
** Remove it from this list before freeing.
**
** Todo: Check the Pager.pStmt list to make sure this is Ok. It
** probably is though.
*/
PgHdr *pTmp;
assert( pPg );
if( pPg==pPager->pAll ){
pPager->pAll = pPg->pNextAll;
}else{
for( pTmp=pPager->pAll; pTmp->pNextAll!=pPg; pTmp=pTmp->pNextAll ){}
pTmp->pNextAll = pPg->pNextAll;
}
nReleased += sqliteAllocSize(pPg);
IOTRACE(("PGFREE %p %d *\n", pPager, pPg->pgno));
PAGER_INCR(sqlite3_pager_pgfree_count);
sqliteFree(pPg);
}
if( rc!=SQLITE_OK ){
/* An error occured whilst writing to the database file or
** journal in pager_recycle(). The error is not returned to the
** caller of this function. Instead, set the Pager.errCode variable.
** The error will be returned to the user (or users, in the case
** of a shared pager cache) of the pager for which the error occured.
*/
assert(
(rc&0xff)==SQLITE_IOERR ||
rc==SQLITE_FULL ||
rc==SQLITE_BUSY
);
assert( pPager->state>=PAGER_RESERVED );
pager_error(pPager, rc);
}
}
}
return nReleased;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT && !SQLITE_OMIT_DISKIO */
/*
** Read the content of page pPg out of the database file.
*/
static int readDbPage(Pager *pPager, PgHdr *pPg, Pgno pgno){
int rc;
assert( MEMDB==0 );
rc = sqlite3OsSeek(pPager->fd, (pgno-1)*(i64)pPager->pageSize);
if( rc==SQLITE_OK ){
rc = sqlite3OsRead(pPager->fd, PGHDR_TO_DATA(pPg),
pPager->pageSize);
}
PAGER_INCR(sqlite3_pager_readdb_count);
PAGER_INCR(pPager->nRead);
IOTRACE(("PGIN %p %d\n", pPager, pgno));
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &((u8*)PGHDR_TO_DATA(pPg))[24],
sizeof(pPager->dbFileVers));
}
CODEC1(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
PAGERTRACE4("FETCH %d page %d hash(%08x)\n",
PAGERID(pPager), pPg->pgno, pager_pagehash(pPg));
return rc;
}
/*
** This function is called to obtain the shared lock required before
** data may be read from the pager cache. If the shared lock has already
** been obtained, this function is a no-op.
**
** Immediately after obtaining the shared lock (if required), this function
** checks for a hot-journal file. If one is found, an emergency rollback
** is performed immediately.
*/
static int pagerSharedLock(Pager *pPager){
int rc = SQLITE_OK;
if( pPager->state==PAGER_UNLOCK ){
if( !MEMDB ){
assert( pPager->nRef==0 );
if( !pPager->noReadlock ){
rc = pager_wait_on_lock(pPager, SHARED_LOCK);
if( rc!=SQLITE_OK ){
return pager_error(pPager, rc);
}
assert( pPager->state>=SHARED_LOCK );
}
/* If a journal file exists, and there is no RESERVED lock on the
** database file, then it either needs to be played back or deleted.
*/
if( hasHotJournal(pPager) ){
/* Get an EXCLUSIVE lock on the database file. At this point it is
** important that a RESERVED lock is not obtained on the way to the
** EXCLUSIVE lock. If it were, another process might open the
** database file, detect the RESERVED lock, and conclude that the
** database is safe to read while this process is still rolling it
** back.
**
** Because the intermediate RESERVED lock is not requested, the
** second process will get to this point in the code and fail to
** obtain it's own EXCLUSIVE lock on the database file.
*/
rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
pager_unlock(pPager);
return pager_error(pPager, rc);
}
pPager->state = PAGER_EXCLUSIVE;
/* Open the journal for reading only. Return SQLITE_BUSY if
** we are unable to open the journal file.
**
** The journal file does not need to be locked itself. The
** journal file is never open unless the main database file holds
** a write lock, so there is never any chance of two or more
** processes opening the journal at the same time.
**
** Open the journal for read/write access. This is because in
** exclusive-access mode the file descriptor will be kept open and
** possibly used for a transaction later on. On some systems, the
** OsTruncate() call used in exclusive-access mode also requires
** a read/write file handle.
*/
rc = SQLITE_BUSY;
if( sqlite3OsFileExists(pPager->zJournal) ){
int ro;
assert( !pPager->tempFile );
rc = sqlite3OsOpenReadWrite(pPager->zJournal, &pPager->jfd, &ro);
assert( rc!=SQLITE_OK || pPager->jfd );
if( ro ){
rc = SQLITE_BUSY;
sqlite3OsClose(&pPager->jfd);
}
}
if( rc!=SQLITE_OK ){
pager_unlock(pPager);
return SQLITE_BUSY;
}
pPager->journalOpen = 1;
pPager->journalStarted = 0;
pPager->journalOff = 0;
pPager->setMaster = 0;
pPager->journalHdr = 0;
/* Playback and delete the journal. Drop the database write
** lock and reacquire the read lock.
*/
rc = pager_playback(pPager, 1);
if( rc!=SQLITE_OK ){
return pager_error(pPager, rc);
}
assert(pPager->state==PAGER_SHARED ||
(pPager->exclusiveMode && pPager->state>PAGER_SHARED)
);
}
if( pPager->pAll ){
/* The shared-lock has just been acquired on the database file
** and there are already pages in the cache (from a previous
** read or write transaction). Check to see if the database
** has been modified. If the database has changed, flush the
** cache.
**
** Database changes is detected by looking at 15 bytes beginning
** at offset 24 into the file. The first 4 of these 16 bytes are
** a 32-bit counter that is incremented with each change. The
** other bytes change randomly with each file change when
** a codec is in use.
**
** There is a vanishingly small chance that a change will not be
** detected. The chance of an undetected change is so small that
** it can be neglected.
*/
char dbFileVers[sizeof(pPager->dbFileVers)];
sqlite3PagerPagecount(pPager);
if( pPager->errCode ){
return pPager->errCode;
}
if( pPager->dbSize>0 ){
IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
rc = sqlite3OsSeek(pPager->fd, 24);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers));
if( rc!=SQLITE_OK ){
return rc;
}
}else{
memset(dbFileVers, 0, sizeof(dbFileVers));
}
if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
pager_reset(pPager);
}
}
}
assert( pPager->exclusiveMode || pPager->state<=PAGER_SHARED );
if( pPager->state==PAGER_UNLOCK ){
pPager->state = PAGER_SHARED;
}
}
return rc;
}
/*
** Allocate a PgHdr object. Either create a new one or reuse
** an existing one that is not otherwise in use.
**
** A new PgHdr structure is created if any of the following are
** true:
**
** (1) We have not exceeded our maximum allocated cache size
** as set by the "PRAGMA cache_size" command.
**
** (2) There are no unused PgHdr objects available at this time.
**
** (3) This is an in-memory database.
**
** (4) There are no PgHdr objects that do not require a journal
** file sync and a sync of the journal file is currently
** prohibited.
**
** Otherwise, reuse an existing PgHdr. In other words, reuse an
** existing PgHdr if all of the following are true:
**
** (1) We have reached or exceeded the maximum cache size
** allowed by "PRAGMA cache_size".
**
** (2) There is a PgHdr available with PgHdr->nRef==0
**
** (3) We are not in an in-memory database
**
** (4) Either there is an available PgHdr that does not need
** to be synced to disk or else disk syncing is currently
** allowed.
*/
static int pagerAllocatePage(Pager *pPager, PgHdr **ppPg){
int rc = SQLITE_OK;
PgHdr *pPg;
/* Create a new PgHdr if any of the four conditions defined
** above is met: */
if( pPager->nPage<pPager->mxPage
|| pPager->pFirst==0
|| MEMDB
|| (pPager->pFirstSynced==0 && pPager->doNotSync)
){
if( pPager->nPage>=pPager->nHash ){
pager_resize_hash_table(pPager,
pPager->nHash<256 ? 256 : pPager->nHash*2);
if( pPager->nHash==0 ){
rc = SQLITE_NOMEM;
goto pager_allocate_out;
}
}
pPg = sqliteMallocRaw( sizeof(*pPg) + pPager->pageSize
+ sizeof(u32) + pPager->nExtra
+ MEMDB*sizeof(PgHistory) );
if( pPg==0 ){
rc = SQLITE_NOMEM;
goto pager_allocate_out;
}
memset(pPg, 0, sizeof(*pPg));
if( MEMDB ){
memset(PGHDR_TO_HIST(pPg, pPager), 0, sizeof(PgHistory));
}
pPg->pPager = pPager;
pPg->pNextAll = pPager->pAll;
pPager->pAll = pPg;
pPager->nPage++;
}else{
/* Recycle an existing page with a zero ref-count. */
rc = pager_recycle(pPager, 1, &pPg);
if( rc==SQLITE_BUSY ){
rc = SQLITE_IOERR_BLOCKED;
}
if( rc!=SQLITE_OK ){
goto pager_allocate_out;
}
assert( pPager->state>=SHARED_LOCK );
assert(pPg);
}
*ppPg = pPg;
pager_allocate_out:
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->needRead ){
int rc = readDbPage(pPg->pPager, pPg, pPg->pgno);
if( rc==SQLITE_OK ){
pPg->needRead = 0;
}else{
return rc;
}
}
return SQLITE_OK;
}
/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired.
** This read lock is dropped when the last page is released.
**
** This routine works for any page number greater than 0. If the database
** file is smaller than the requested page, then no actual disk
** read occurs and the memory image of the page is initialized to
** all zeros. The extra data appended to a page is always initialized
** to zeros the first time a page is loaded into memory.
**
** The acquisition might fail for several reasons. In all cases,
** an appropriate error code is returned and *ppPage is set to NULL.
**
** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt
** to find a page in the in-memory cache first. If the page is not already
** in memory, this routine goes to disk to read it in whereas Lookup()
** just returns 0. This routine acquires a read-lock the first time it
** has to go to disk, and could also playback an old journal if necessary.
** Since Lookup() never goes to disk, it never has to deal with locks
** or journal files.
**
** If noContent is false, the page contents are actually read from disk.
** If noContent is true, it means that we do not care about the contents
** of the page at this time, so do not do a disk read. Just fill in the
** page content with zeros. But mark the fact that we have not read the
** content by setting the PgHdr.needRead flag. Later on, if
** sqlite3PagerWrite() is called on this page or if this routine is
** called again with noContent==0, that means that the content is needed
** and the disk read should occur at that point.
*/
int sqlite3PagerAcquire(
Pager *pPager, /* The pager open on the database file */
Pgno pgno, /* Page number to fetch */
DbPage **ppPage, /* Write a pointer to the page here */
int noContent /* Do not bother reading content from disk if true */
){
PgHdr *pPg;
int rc;
assert( pPager->state==PAGER_UNLOCK || pPager->nRef>0 || pgno==1 );
/* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
** number greater than this, or zero, is requested.
*/
if( pgno>PAGER_MAX_PGNO || pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
return SQLITE_CORRUPT_BKPT;
}
/* Make sure we have not hit any critical errors.
*/
assert( pPager!=0 );
*ppPage = 0;
if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
return pPager->errCode;
}
/* If this is the first page accessed, then get a SHARED lock
** on the database file. pagerSharedLock() is a no-op if
** a database lock is already held.
*/
rc = pagerSharedLock(pPager);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pPager->state!=PAGER_UNLOCK );
pPg = pager_lookup(pPager, pgno);
if( pPg==0 ){
/* The requested page is not in the page cache. */
int nMax;
int h;
PAGER_INCR(pPager->nMiss);
rc = pagerAllocatePage(pPager, &pPg);
if( rc!=SQLITE_OK ){
return rc;
}
pPg->pgno = pgno;
assert( !MEMDB || pgno>pPager->stmtSize );
if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
sqlite3CheckMemory(pPager->aInJournal, pgno/8);
assert( pPager->journalOpen );
pPg->inJournal = (pPager->aInJournal[pgno/8] & (1<<(pgno&7)))!=0;
pPg->needSync = 0;
}else{
pPg->inJournal = 0;
pPg->needSync = 0;
}
makeClean(pPg);
pPg->nRef = 1;
REFINFO(pPg);
pPager->nRef++;
if( pPager->nExtra>0 ){
memset(PGHDR_TO_EXTRA(pPg, pPager), 0, pPager->nExtra);
}
nMax = sqlite3PagerPagecount(pPager);
if( pPager->errCode ){
sqlite3PagerUnref(pPg);
rc = pPager->errCode;
return rc;
}
/* Populate the page with data, either by reading from the database
** file, or by setting the entire page to zero.
*/
if( nMax<(int)pgno || MEMDB || (noContent && !pPager->alwaysRollback) ){
if( pgno>pPager->mxPgno ){
sqlite3PagerUnref(pPg);
return SQLITE_FULL;
}
memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
pPg->needRead = noContent && !pPager->alwaysRollback;
IOTRACE(("ZERO %p %d\n", pPager, pgno));
}else{
rc = readDbPage(pPager, pPg, pgno);
if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
pPg->pgno = 0;
sqlite3PagerUnref(pPg);
return rc;
}
pPg->needRead = 0;
}
/* Link the page into the page hash table */
h = pgno & (pPager->nHash-1);
assert( pgno!=0 );
pPg->pNextHash = pPager->aHash[h];
pPager->aHash[h] = pPg;
if( pPg->pNextHash ){
assert( pPg->pNextHash->pPrevHash==0 );
pPg->pNextHash->pPrevHash = pPg;
}
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
}else{
/* The requested page is in the page cache. */
assert(pPager->nRef>0 || pgno==1);
PAGER_INCR(pPager->nHit);
if( !noContent ){
rc = pager_get_content(pPg);
if( rc ){
return rc;
}
}
page_ref(pPg);
}
*ppPage = pPg;
return SQLITE_OK;
}
/*
** Acquire a page if it is already in the in-memory cache. Do
** not read the page from disk. Return a pointer to the page,
** or 0 if the page is not in cache.
**
** See also sqlite3PagerGet(). The difference between this routine
** and sqlite3PagerGet() is that _get() will go to the disk and read
** in the page if the page is not already in cache. This routine
** returns NULL if the page is not in cache or if a disk I/O error
** has ever happened.
*/
DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
PgHdr *pPg;
assert( pPager!=0 );
assert( pgno!=0 );
if( pPager->state==PAGER_UNLOCK ){
assert( !pPager->pAll || pPager->exclusiveMode );
return 0;
}
if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
return 0;
}
pPg = pager_lookup(pPager, pgno);
if( pPg==0 ) return 0;
page_ref(pPg);
return pPg;
}
/*
** Release a page.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list. When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
int sqlite3PagerUnref(DbPage *pPg){
/* Decrement the reference count for this page
*/
assert( pPg->nRef>0 );
pPg->nRef--;
REFINFO(pPg);
CHECK_PAGE(pPg);
/* When the number of references to a page reach 0, call the
** destructor and add the page to the freelist.
*/
if( pPg->nRef==0 ){
Pager *pPager;
pPager = pPg->pPager;
pPg->pNextFree = 0;
pPg->pPrevFree = pPager->pLast;
pPager->pLast = pPg;
if( pPg->pPrevFree ){
pPg->pPrevFree->pNextFree = pPg;
}else{
pPager->pFirst = pPg;
}
if( pPg->needSync==0 && pPager->pFirstSynced==0 ){
pPager->pFirstSynced = pPg;
}
if( pPager->xDestructor ){
pPager->xDestructor(pPg, pPager->pageSize);
}
/* When all pages reach the freelist, drop the read lock from
** the database file.
*/
pPager->nRef--;
assert( pPager->nRef>=0 );
if( pPager->nRef==0 && (!pPager->exclusiveMode || pPager->journalOff>0) ){
pagerUnlockAndRollback(pPager);
}
}
return SQLITE_OK;
}
/*
** Create a journal file for pPager. There should already be a RESERVED
** or EXCLUSIVE lock on the database file when this routine is called.
**
** Return SQLITE_OK if everything. Return an error code and release the
** write lock if anything goes wrong.
*/
static int pager_open_journal(Pager *pPager){
int rc;
assert( !MEMDB );
assert( pPager->state>=PAGER_RESERVED );
assert( pPager->journalOpen==0 );
assert( pPager->useJournal );
assert( pPager->aInJournal==0 );
sqlite3PagerPagecount(pPager);
pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
if( pPager->aInJournal==0 ){
rc = SQLITE_NOMEM;
goto failed_to_open_journal;
}
rc = sqlite3OsOpenExclusive(pPager->zJournal, &pPager->jfd,
pPager->tempFile);
assert( rc!=SQLITE_OK || pPager->jfd );
pPager->journalOff = 0;
pPager->setMaster = 0;
pPager->journalHdr = 0;
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM ){
sqlite3OsDelete(pPager->zJournal);
}
goto failed_to_open_journal;
}
sqlite3OsSetFullSync(pPager->jfd, pPager->full_fsync);
sqlite3OsSetFullSync(pPager->fd, pPager->full_fsync);
sqlite3OsOpenDirectory(pPager->jfd, pPager->zDirectory);
pPager->journalOpen = 1;
pPager->journalStarted = 0;
pPager->needSync = 0;
pPager->alwaysRollback = 0;
pPager->nRec = 0;
if( pPager->errCode ){
rc = pPager->errCode;
goto failed_to_open_journal;
}
pPager->origDbSize = pPager->dbSize;
rc = writeJournalHdr(pPager);
if( pPager->stmtAutoopen && rc==SQLITE_OK ){
rc = sqlite3PagerStmtBegin(pPager);
}
if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM ){
rc = pager_end_transaction(pPager);
if( rc==SQLITE_OK ){
rc = SQLITE_FULL;
}
}
return rc;
failed_to_open_journal:
sqliteFree(pPager->aInJournal);
pPager->aInJournal = 0;
return rc;
}
/*
** Acquire a write-lock on the database. The lock is removed when
** the any of the following happen:
**
** * sqlite3PagerCommitPhaseTwo() is called.
** * sqlite3PagerRollback() is called.
** * sqlite3PagerClose() is called.
** * sqlite3PagerUnref() is called to on every outstanding page.
**
** The first parameter to this routine is a pointer to any open page of the
** database file. Nothing changes about the page - it is used merely to
** acquire a pointer to the Pager structure and as proof that there is
** already a read-lock on the database.
**
** The second parameter indicates how much space in bytes to reserve for a
** master journal file-name at the start of the journal when it is created.
**
** A journal file is opened if this is not a temporary file. For temporary
** files, the opening of the journal file is deferred until there is an
** actual need to write to the journal.
**
** If the database is already reserved for writing, this routine is a no-op.
**
** If exFlag is true, go ahead and get an EXCLUSIVE lock on the file
** immediately instead of waiting until we try to flush the cache. The
** exFlag is ignored if a transaction is already active.
*/
int sqlite3PagerBegin(DbPage *pPg, int exFlag){
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
assert( pPg->nRef>0 );
assert( pPager->state!=PAGER_UNLOCK );
if( pPager->state==PAGER_SHARED ){
assert( pPager->aInJournal==0 );
if( MEMDB ){
pPager->state = PAGER_EXCLUSIVE;
pPager->origDbSize = pPager->dbSize;
}else{
rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
if( rc==SQLITE_OK ){
pPager->state = PAGER_RESERVED;
if( exFlag ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
if( rc!=SQLITE_OK ){
return rc;
}
pPager->dirtyCache = 0;
PAGERTRACE2("TRANSACTION %d\n", PAGERID(pPager));
if( pPager->useJournal && !pPager->tempFile ){
rc = pager_open_journal(pPager);
}
}
}else if( pPager->journalOpen && pPager->journalOff==0 ){
/* This happens when the pager was in exclusive-access mode last
** time a (read or write) transaction was successfully concluded
** by this connection. Instead of deleting the journal file it was
** kept open and truncated to 0 bytes.
*/
assert( pPager->nRec==0 );
assert( pPager->origDbSize==0 );
assert( pPager->aInJournal==0 );
sqlite3PagerPagecount(pPager);
pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
if( !pPager->aInJournal ){
rc = SQLITE_NOMEM;
}else{
pPager->origDbSize = pPager->dbSize;
rc = writeJournalHdr(pPager);
}
}
assert( !pPager->journalOpen || pPager->journalOff>0 || rc!=SQLITE_OK );
return rc;
}
/*
** Make a page dirty. Set its dirty flag and add it to the dirty
** page list.
*/
static void makeDirty(PgHdr *pPg){
if( pPg->dirty==0 ){
Pager *pPager = pPg->pPager;
pPg->dirty = 1;
pPg->pDirty = pPager->pDirty;
if( pPager->pDirty ){
pPager->pDirty->pPrevDirty = pPg;
}
pPg->pPrevDirty = 0;
pPager->pDirty = pPg;
}
}
/*
** Make a page clean. Clear its dirty bit and remove it from the
** dirty page list.
*/
static void makeClean(PgHdr *pPg){
if( pPg->dirty ){
pPg->dirty = 0;
if( pPg->pDirty ){
pPg->pDirty->pPrevDirty = pPg->pPrevDirty;
}
if( pPg->pPrevDirty ){
pPg->pPrevDirty->pDirty = pPg->pDirty;
}else{
pPg->pPager->pDirty = pPg->pDirty;
}
}
}
/*
** Mark a data page as writeable. The page is written into the journal
** if it is not there already. This routine must be called before making
** changes to a page.
**
** The first time this routine is called, the pager creates a new
** journal and acquires a RESERVED lock on the database. If the RESERVED
** lock could not be acquired, this routine returns SQLITE_BUSY. The
** calling routine must check for that return value and be careful not to
** change any page data until this routine returns SQLITE_OK.
**
** If the journal file could not be written because the disk is full,
** then this routine returns SQLITE_FULL and does an immediate rollback.
** All subsequent write attempts also return SQLITE_FULL until there
** is a call to sqlite3PagerCommit() or sqlite3PagerRollback() to
** reset.
*/
static int pager_write(PgHdr *pPg){
void *pData = PGHDR_TO_DATA(pPg);
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
/* Check for errors
*/
if( pPager->errCode ){
return pPager->errCode;
}
if( pPager->readOnly ){
return SQLITE_PERM;
}
assert( !pPager->setMaster );
CHECK_PAGE(pPg);
/* If this page was previously acquired with noContent==1, that means
** we didn't really read in the content of the page. This can happen
** (for example) when the page is being moved to the freelist. But
** now we are (perhaps) moving the page off of the freelist for
** reuse and we need to know its original content so that content
** can be stored in the rollback journal. So do the read at this
** time.
*/
rc = pager_get_content(pPg);
if( rc ){
return rc;
}
/* Mark the page as dirty. If the page has already been written
** to the journal then we can return right away.
*/
makeDirty(pPg);
if( pPg->inJournal && (pageInStatement(pPg) || pPager->stmtInUse==0) ){
pPager->dirtyCache = 1;
}else{
/* If we get this far, it means that the page needs to be
** written to the transaction journal or the ckeckpoint journal
** or both.
**
** First check to see that the transaction journal exists and
** create it if it does not.
*/
assert( pPager->state!=PAGER_UNLOCK );
rc = sqlite3PagerBegin(pPg, 0);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pPager->state>=PAGER_RESERVED );
if( !pPager->journalOpen && pPager->useJournal ){
rc = pager_open_journal(pPager);
if( rc!=SQLITE_OK ) return rc;
}
assert( pPager->journalOpen || !pPager->useJournal );
pPager->dirtyCache = 1;
/* The transaction journal now exists and we have a RESERVED or an
** EXCLUSIVE lock on the main database file. Write the current page to
** the transaction journal if it is not there already.
*/
if( !pPg->inJournal && (pPager->useJournal || MEMDB) ){
if( (int)pPg->pgno <= pPager->origDbSize ){
int szPg;
if( MEMDB ){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
PAGERTRACE3("JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);
assert( pHist->pOrig==0 );
pHist->pOrig = sqliteMallocRaw( pPager->pageSize );
if( pHist->pOrig ){
memcpy(pHist->pOrig, PGHDR_TO_DATA(pPg), pPager->pageSize);
}
}else{
u32 cksum, saved;
char *pData2, *pEnd;
/* We should never write to the journal file the page that
** contains the database locks. The following assert verifies
** that we do not. */
assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
cksum = pager_cksum(pPager, (u8*)pData2);
pEnd = pData2 + pPager->pageSize;
pData2 -= 4;
saved = *(u32*)pEnd;
put32bits(pEnd, cksum);
szPg = pPager->pageSize+8;
put32bits(pData2, pPg->pgno);
rc = sqlite3OsWrite(pPager->jfd, pData2, szPg);
IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno,
pPager->journalOff, szPg));
PAGER_INCR(sqlite3_pager_writej_count);
pPager->journalOff += szPg;
PAGERTRACE5("JOURNAL %d page %d needSync=%d hash(%08x)\n",
PAGERID(pPager), pPg->pgno, pPg->needSync, pager_pagehash(pPg));
*(u32*)pEnd = saved;
/* An error has occured writing to the journal file. The
** transaction will be rolled back by the layer above.
*/
if( rc!=SQLITE_OK ){
return rc;
}
pPager->nRec++;
assert( pPager->aInJournal!=0 );
pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
pPg->needSync = !pPager->noSync;
if( pPager->stmtInUse ){
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
}
}
}else{
pPg->needSync = !pPager->journalStarted && !pPager->noSync;
PAGERTRACE4("APPEND %d page %d needSync=%d\n",
PAGERID(pPager), pPg->pgno, pPg->needSync);
}
if( pPg->needSync ){
pPager->needSync = 1;
}
pPg->inJournal = 1;
}
/* If the statement journal is open and the page is not in it,
** then write the current page to the statement journal. Note that
** the statement journal format differs from the standard journal format
** in that it omits the checksums and the header.
*/
if( pPager->stmtInUse
&& !pageInStatement(pPg)
&& (int)pPg->pgno<=pPager->stmtSize
){
assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
if( MEMDB ){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
assert( pHist->pStmt==0 );
pHist->pStmt = sqliteMallocRaw( pPager->pageSize );
if( pHist->pStmt ){
memcpy(pHist->pStmt, PGHDR_TO_DATA(pPg), pPager->pageSize);
}
PAGERTRACE3("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);
page_add_to_stmt_list(pPg);
}else{
char *pData2 = CODEC2(pPager, pData, pPg->pgno, 7)-4;
put32bits(pData2, pPg->pgno);
rc = sqlite3OsWrite(pPager->stfd, pData2, pPager->pageSize+4);
PAGERTRACE3("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);
if( rc!=SQLITE_OK ){
return rc;
}
pPager->stmtNRec++;
assert( pPager->aInStmt!=0 );
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
}
}
}
/* Update the database size and return.
*/
assert( pPager->state>=PAGER_SHARED );
if( pPager->dbSize<(int)pPg->pgno ){
pPager->dbSize = pPg->pgno;
if( !MEMDB && pPager->dbSize==PENDING_BYTE/pPager->pageSize ){
pPager->dbSize++;
}
}
return rc;
}
/*
** This function is used to mark a data-page as writable. It uses
** pager_write() to open a journal file (if it is not already open)
** and write the page *pData to the journal.
**
** The difference between this function and pager_write() is that this
** function also deals with the special case where 2 or more pages
** fit on a single disk sector. In this case all co-resident pages
** must have been written to the journal file before returning.
*/
int sqlite3PagerWrite(DbPage *pDbPage){
int rc = SQLITE_OK;
PgHdr *pPg = pDbPage;
Pager *pPager = pPg->pPager;
Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
if( !MEMDB && nPagePerSector>1 ){
Pgno nPageCount; /* Total number of pages in database file */
Pgno pg1; /* First page of the sector pPg is located on. */
int nPage; /* Number of pages starting at pg1 to journal */
int ii;
/* Set the doNotSync flag to 1. This is because we cannot allow a journal
** header to be written between the pages journaled by this function.
*/
assert( pPager->doNotSync==0 );
pPager->doNotSync = 1;
/* This trick assumes that both the page-size and sector-size are
** an integer power of 2. It sets variable pg1 to the identifier
** of the first page of the sector pPg is located on.
*/
pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
nPageCount = sqlite3PagerPagecount(pPager);
if( pPg->pgno>nPageCount ){
nPage = (pPg->pgno - pg1)+1;
}else if( (pg1+nPagePerSector-1)>nPageCount ){
nPage = nPageCount+1-pg1;
}else{
nPage = nPagePerSector;
}
assert(nPage>0);
assert(pg1<=pPg->pgno);
assert((pg1+nPage)>pPg->pgno);
for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
Pgno pg = pg1+ii;
if( !pPager->aInJournal || pg==pPg->pgno ||
pg>pPager->origDbSize || !(pPager->aInJournal[pg/8]&(1<<(pg&7)))
) {
if( pg!=PAGER_MJ_PGNO(pPager) ){
PgHdr *pPage;
rc = sqlite3PagerGet(pPager, pg, &pPage);
if( rc==SQLITE_OK ){
rc = pager_write(pPage);
sqlite3PagerUnref(pPage);
}
}
}
}
assert( pPager->doNotSync==1 );
pPager->doNotSync = 0;
}else{
rc = pager_write(pDbPage);
}
return rc;
}
/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3PagerWrite(). In other words, return TRUE if it is ok
** to change the content of the page.
*/
#ifndef NDEBUG
int sqlite3PagerIswriteable(DbPage *pPg){
return pPg->dirty;
}
#endif
#ifndef SQLITE_OMIT_VACUUM
/*
** Replace the content of a single page with the information in the third
** argument.
*/
int sqlite3PagerOverwrite(Pager *pPager, Pgno pgno, void *pData){
PgHdr *pPg;
int rc;
rc = sqlite3PagerGet(pPager, pgno, &pPg);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pPg);
if( rc==SQLITE_OK ){
memcpy(sqlite3PagerGetData(pPg), pData, pPager->pageSize);
}
sqlite3PagerUnref(pPg);
}
return rc;
}
#endif
/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page pPg back to the disk, even though
** that page might be marked as dirty.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused. The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization, together with the
** sqlite3PagerDontRollback() below, more than double the speed
** of large INSERT operations and quadruple the speed of large DELETEs.
**
** When this routine is called, set the alwaysRollback flag to true.
** Subsequent calls to sqlite3PagerDontRollback() for the same page
** will thereafter be ignored. This is necessary to avoid a problem
** where a page with data is added to the freelist during one part of
** a transaction then removed from the freelist during a later part
** of the same transaction and reused for some other purpose. When it
** is first added to the freelist, this routine is called. When reused,
** the sqlite3PagerDontRollback() routine is called. But because the
** page contains critical data, we still need to be sure it gets
** rolled back in spite of the sqlite3PagerDontRollback() call.
*/
void sqlite3PagerDontWrite(DbPage *pDbPage){
PgHdr *pPg = pDbPage;
Pager *pPager = pPg->pPager;
if( MEMDB ) return;
pPg->alwaysRollback = 1;
if( pPg->dirty && !pPager->stmtInUse ){
assert( pPager->state>=PAGER_SHARED );
if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
/* If this pages is the last page in the file and the file has grown
** during the current transaction, then do NOT mark the page as clean.
** When the database file grows, we must make sure that the last page
** gets written at least once so that the disk file will be the correct
** size. If you do not write this page and the size of the file
** on the disk ends up being too small, that can lead to database
** corruption during the next transaction.
*/
}else{
PAGERTRACE3("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager));
IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
makeClean(pPg);
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
}
}
}
/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page. This
** means that the pager does not have to record the given page in the
** rollback journal.
**
** If we have not yet actually read the content of this page (if
** the PgHdr.needRead flag is set) then this routine acts as a promise
** that we will never need to read the page content in the future.
** so the needRead flag can be cleared at this point.
*/
void sqlite3PagerDontRollback(DbPage *pPg){
Pager *pPager = pPg->pPager;
assert( pPager->state>=PAGER_RESERVED );
if( pPager->journalOpen==0 ) return;
if( pPg->alwaysRollback || pPager->alwaysRollback || MEMDB ) return;
if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){
assert( pPager->aInJournal!=0 );
pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
pPg->inJournal = 1;
pPg->needRead = 0;
if( pPager->stmtInUse ){
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
}
PAGERTRACE3("DONT_ROLLBACK page %d of %d\n", pPg->pgno, PAGERID(pPager));
IOTRACE(("GARBAGE %p %d\n", pPager, pPg->pgno))
}
if( pPager->stmtInUse
&& !pageInStatement(pPg)
&& (int)pPg->pgno<=pPager->stmtSize
){
assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
assert( pPager->aInStmt!=0 );
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
}
}
/*
** This routine is called to increment the database file change-counter,
** stored at byte 24 of the pager file.
*/
static int pager_incr_changecounter(Pager *pPager){
PgHdr *pPgHdr;
u32 change_counter;
int rc;
if( !pPager->changeCountDone ){
/* Open page 1 of the file for writing. */
rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3PagerWrite(pPgHdr);
if( rc!=SQLITE_OK ) return rc;
/* Increment the value just read and write it back to byte 24. */
change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers);
change_counter++;
put32bits(((char*)PGHDR_TO_DATA(pPgHdr))+24, change_counter);
/* Release the page reference. */
sqlite3PagerUnref(pPgHdr);
pPager->changeCountDone = 1;
}
return SQLITE_OK;
}
/*
** Sync the database file for the pager pPager. zMaster points to the name
** of a master journal file that should be written into the individual
** journal file. zMaster may be NULL, which is interpreted as no master
** journal (a single database transaction).
**
** This routine ensures that the journal is synced, all dirty pages written
** to the database file and the database file synced. The only thing that
** remains to commit the transaction is to delete the journal file (or
** master journal file if specified).
**
** Note that if zMaster==NULL, this does not overwrite a previous value
** passed to an sqlite3PagerCommitPhaseOne() call.
**
** If parameter nTrunc is non-zero, then the pager file is truncated to
** nTrunc pages (this is used by auto-vacuum databases).
*/
int sqlite3PagerCommitPhaseOne(Pager *pPager, const char *zMaster, Pgno nTrunc){
int rc = SQLITE_OK;
PAGERTRACE4("DATABASE SYNC: File=%s zMaster=%s nTrunc=%d\n",
pPager->zFilename, zMaster, nTrunc);
/* If this is an in-memory db, or no pages have been written to, or this
** function has already been called, it is a no-op.
*/
if( pPager->state!=PAGER_SYNCED && !MEMDB && pPager->dirtyCache ){
PgHdr *pPg;
assert( pPager->journalOpen );
/* If a master journal file name has already been written to the
** journal file, then no sync is required. This happens when it is
** written, then the process fails to upgrade from a RESERVED to an
** EXCLUSIVE lock. The next time the process tries to commit the
** transaction the m-j name will have already been written.
*/
if( !pPager->setMaster ){
rc = pager_incr_changecounter(pPager);
if( rc!=SQLITE_OK ) goto sync_exit;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( nTrunc!=0 ){
/* If this transaction has made the database smaller, then all pages
** being discarded by the truncation must be written to the journal
** file.
*/
Pgno i;
int iSkip = PAGER_MJ_PGNO(pPager);
for( i=nTrunc+1; i<=pPager->origDbSize; i++ ){
if( !(pPager->aInJournal[i/8] & (1<<(i&7))) && i!=iSkip ){
rc = sqlite3PagerGet(pPager, i, &pPg);
if( rc!=SQLITE_OK ) goto sync_exit;
rc = sqlite3PagerWrite(pPg);
sqlite3PagerUnref(pPg);
if( rc!=SQLITE_OK ) goto sync_exit;
}
}
}
#endif
rc = writeMasterJournal(pPager, zMaster);
if( rc!=SQLITE_OK ) goto sync_exit;
rc = syncJournal(pPager);
if( rc!=SQLITE_OK ) goto sync_exit;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
if( nTrunc!=0 ){
rc = sqlite3PagerTruncate(pPager, nTrunc);
if( rc!=SQLITE_OK ) goto sync_exit;
}
#endif
/* Write all dirty pages to the database file */
pPg = pager_get_all_dirty_pages(pPager);
rc = pager_write_pagelist(pPg);
if( rc!=SQLITE_OK ) goto sync_exit;
pPager->pDirty = 0;
/* Sync the database file. */
if( !pPager->noSync ){
rc = sqlite3OsSync(pPager->fd, 0);
}
IOTRACE(("DBSYNC %p\n", pPager))
pPager->state = PAGER_SYNCED;
}else if( MEMDB && nTrunc!=0 ){
rc = sqlite3PagerTruncate(pPager, nTrunc);
}
sync_exit:
if( rc==SQLITE_IOERR_BLOCKED ){
/* pager_incr_changecounter() may attempt to obtain an exclusive
* lock to spill the cache and return IOERR_BLOCKED. But since
* there is no chance the cache is inconsistent, it's
* better to return SQLITE_BUSY.
*/
rc = SQLITE_BUSY;
}
return rc;
}
/*
** Commit all changes to the database and release the write lock.
**
** If the commit fails for any reason, a rollback attempt is made
** and an error code is returned. If the commit worked, SQLITE_OK
** is returned.
*/
int sqlite3PagerCommitPhaseTwo(Pager *pPager){
int rc;
PgHdr *pPg;
if( pPager->errCode ){
return pPager->errCode;
}
if( pPager->state<PAGER_RESERVED ){
return SQLITE_ERROR;
}
PAGERTRACE2("COMMIT %d\n", PAGERID(pPager));
if( MEMDB ){
pPg = pager_get_all_dirty_pages(pPager);
while( pPg ){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
clearHistory(pHist);
pPg->dirty = 0;
pPg->inJournal = 0;
pHist->inStmt = 0;
pPg->needSync = 0;
pHist->pPrevStmt = pHist->pNextStmt = 0;
pPg = pPg->pDirty;
}
pPager->pDirty = 0;
#ifndef NDEBUG
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
assert( !pPg->alwaysRollback );
assert( !pHist->pOrig );
assert( !pHist->pStmt );
}
#endif
pPager->pStmt = 0;
pPager->state = PAGER_SHARED;
return SQLITE_OK;
}
assert( pPager->journalOpen || !pPager->dirtyCache );
assert( pPager->state==PAGER_SYNCED || !pPager->dirtyCache );
rc = pager_end_transaction(pPager);
return pager_error(pPager, rc);
}
/*
** Rollback all changes. The database falls back to PAGER_SHARED mode.
** All in-memory cache pages revert to their original data contents.
** The journal is deleted.
**
** This routine cannot fail unless some other process is not following
** the correct locking protocol or unless some other
** process is writing trash into the journal file (SQLITE_CORRUPT) or
** unless a prior malloc() failed (SQLITE_NOMEM). Appropriate error
** codes are returned for all these occasions. Otherwise,
** SQLITE_OK is returned.
*/
int sqlite3PagerRollback(Pager *pPager){
int rc;
PAGERTRACE2("ROLLBACK %d\n", PAGERID(pPager));
if( MEMDB ){
PgHdr *p;
for(p=pPager->pAll; p; p=p->pNextAll){
PgHistory *pHist;
assert( !p->alwaysRollback );
if( !p->dirty ){
assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pOrig );
assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pStmt );
continue;
}
pHist = PGHDR_TO_HIST(p, pPager);
if( pHist->pOrig ){
memcpy(PGHDR_TO_DATA(p), pHist->pOrig, pPager->pageSize);
PAGERTRACE3("ROLLBACK-PAGE %d of %d\n", p->pgno, PAGERID(pPager));
}else{
PAGERTRACE3("PAGE %d is clean on %d\n", p->pgno, PAGERID(pPager));
}
clearHistory(pHist);
p->dirty = 0;
p->inJournal = 0;
pHist->inStmt = 0;
pHist->pPrevStmt = pHist->pNextStmt = 0;
if( pPager->xReiniter ){
pPager->xReiniter(p, pPager->pageSize);
}
}
pPager->pDirty = 0;
pPager->pStmt = 0;
pPager->dbSize = pPager->origDbSize;
pager_truncate_cache(pPager);
pPager->stmtInUse = 0;
pPager->state = PAGER_SHARED;
return SQLITE_OK;
}
if( !pPager->dirtyCache || !pPager->journalOpen ){
rc = pager_end_transaction(pPager);
return rc;
}
if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
if( pPager->state>=PAGER_EXCLUSIVE ){
pager_playback(pPager, 0);
}
return pPager->errCode;
}
if( pPager->state==PAGER_RESERVED ){
int rc2;
rc = pager_playback(pPager, 0);
rc2 = pager_end_transaction(pPager);
if( rc==SQLITE_OK ){
rc = rc2;
}
}else{
rc = pager_playback(pPager, 0);
}
/* pager_reset(pPager); */
pPager->dbSize = -1;
/* If an error occurs during a ROLLBACK, we can no longer trust the pager
** cache. So call pager_error() on the way out to make any error
** persistent.
*/
return pager_error(pPager, rc);
}
/*
** Return TRUE if the database file is opened read-only. Return FALSE
** if the database is (in theory) writable.
*/
int sqlite3PagerIsreadonly(Pager *pPager){
return pPager->readOnly;
}
/*
** Return the number of references to the pager.
*/
int sqlite3PagerRefcount(Pager *pPager){
return pPager->nRef;
}
#ifdef SQLITE_TEST
/*
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
static int a[11];
a[0] = pPager->nRef;
a[1] = pPager->nPage;
a[2] = pPager->mxPage;
a[3] = pPager->dbSize;
a[4] = pPager->state;
a[5] = pPager->errCode;
a[6] = pPager->nHit;
a[7] = pPager->nMiss;
a[8] = 0; /* Used to be pPager->nOvfl */
a[9] = pPager->nRead;
a[10] = pPager->nWrite;
return a;
}
#endif
/*
** Set the statement rollback point.
**
** This routine should be called with the transaction journal already
** open. A new statement journal is created that can be used to rollback
** changes of a single SQL command within a larger transaction.
*/
int sqlite3PagerStmtBegin(Pager *pPager){
int rc;
assert( !pPager->stmtInUse );
assert( pPager->state>=PAGER_SHARED );
assert( pPager->dbSize>=0 );
PAGERTRACE2("STMT-BEGIN %d\n", PAGERID(pPager));
if( MEMDB ){
pPager->stmtInUse = 1;
pPager->stmtSize = pPager->dbSize;
return SQLITE_OK;
}
if( !pPager->journalOpen ){
pPager->stmtAutoopen = 1;
return SQLITE_OK;
}
assert( pPager->journalOpen );
pPager->aInStmt = sqliteMalloc( pPager->dbSize/8 + 1 );
if( pPager->aInStmt==0 ){
/* sqlite3OsLock(pPager->fd, SHARED_LOCK); */
return SQLITE_NOMEM;
}
#ifndef NDEBUG
rc = sqlite3OsFileSize(pPager->jfd, &pPager->stmtJSize);
if( rc ) goto stmt_begin_failed;
assert( pPager->stmtJSize == pPager->journalOff );
#endif
pPager->stmtJSize = pPager->journalOff;
pPager->stmtSize = pPager->dbSize;
pPager->stmtHdrOff = 0;
pPager->stmtCksum = pPager->cksumInit;
if( !pPager->stmtOpen ){
rc = sqlite3PagerOpentemp(&pPager->stfd);
if( rc ) goto stmt_begin_failed;
pPager->stmtOpen = 1;
pPager->stmtNRec = 0;
}
pPager->stmtInUse = 1;
return SQLITE_OK;
stmt_begin_failed:
if( pPager->aInStmt ){
sqliteFree(pPager->aInStmt);
pPager->aInStmt = 0;
}
return rc;
}
/*
** Commit a statement.
*/
int sqlite3PagerStmtCommit(Pager *pPager){
if( pPager->stmtInUse ){
PgHdr *pPg, *pNext;
PAGERTRACE2("STMT-COMMIT %d\n", PAGERID(pPager));
if( !MEMDB ){
sqlite3OsSeek(pPager->stfd, 0);
/* sqlite3OsTruncate(pPager->stfd, 0); */
sqliteFree( pPager->aInStmt );
pPager->aInStmt = 0;
}else{
for(pPg=pPager->pStmt; pPg; pPg=pNext){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
pNext = pHist->pNextStmt;
assert( pHist->inStmt );
pHist->inStmt = 0;
pHist->pPrevStmt = pHist->pNextStmt = 0;
sqliteFree(pHist->pStmt);
pHist->pStmt = 0;
}
}
pPager->stmtNRec = 0;
pPager->stmtInUse = 0;
pPager->pStmt = 0;
}
pPager->stmtAutoopen = 0;
return SQLITE_OK;
}
/*
** Rollback a statement.
*/
int sqlite3PagerStmtRollback(Pager *pPager){
int rc;
if( pPager->stmtInUse ){
PAGERTRACE2("STMT-ROLLBACK %d\n", PAGERID(pPager));
if( MEMDB ){
PgHdr *pPg;
PgHistory *pHist;
for(pPg=pPager->pStmt; pPg; pPg=pHist->pNextStmt){
pHist = PGHDR_TO_HIST(pPg, pPager);
if( pHist->pStmt ){
memcpy(PGHDR_TO_DATA(pPg), pHist->pStmt, pPager->pageSize);
sqliteFree(pHist->pStmt);
pHist->pStmt = 0;
}
}
pPager->dbSize = pPager->stmtSize;
pager_truncate_cache(pPager);
rc = SQLITE_OK;
}else{
rc = pager_stmt_playback(pPager);
}
sqlite3PagerStmtCommit(pPager);
}else{
rc = SQLITE_OK;
}
pPager->stmtAutoopen = 0;
return rc;
}
/*
** Return the full pathname of the database file.
*/
const char *sqlite3PagerFilename(Pager *pPager){
return pPager->zFilename;
}
/*
** Return the directory of the database file.
*/
const char *sqlite3PagerDirname(Pager *pPager){
return pPager->zDirectory;
}
/*
** Return the full pathname of the journal file.
*/
const char *sqlite3PagerJournalname(Pager *pPager){
return pPager->zJournal;
}
/*
** Return true if fsync() calls are disabled for this pager. Return FALSE
** if fsync()s are executed normally.
*/
int sqlite3PagerNosync(Pager *pPager){
return pPager->noSync;
}
#ifdef SQLITE_HAS_CODEC
/*
** Set the codec for this pager
*/
void sqlite3PagerSetCodec(
Pager *pPager,
void *(*xCodec)(void*,void*,Pgno,int),
void *pCodecArg
){
pPager->xCodec = xCodec;
pPager->pCodecArg = pCodecArg;
}
#endif
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Move the page pPg to location pgno in the file.
**
** There must be no references to the page previously located at
** pgno (which we call pPgOld) though that page is allowed to be
** in cache. If the page previous located at pgno is not already
** in the rollback journal, it is not put there by by this routine.
**
** References to the page pPg remain valid. Updating any
** meta-data associated with pPg (i.e. data stored in the nExtra bytes
** allocated along with the page) is the responsibility of the caller.
**
** A transaction must be active when this routine is called. It used to be
** required that a statement transaction was not active, but this restriction
** has been removed (CREATE INDEX needs to move a page when a statement
** transaction is active).
*/
int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno){
PgHdr *pPgOld; /* The page being overwritten. */
int h;
Pgno needSyncPgno = 0;
assert( pPg->nRef>0 );
PAGERTRACE5("MOVE %d page %d (needSync=%d) moves to %d\n",
PAGERID(pPager), pPg->pgno, pPg->needSync, pgno);
IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
pager_get_content(pPg);
if( pPg->needSync ){
needSyncPgno = pPg->pgno;
assert( pPg->inJournal || (int)pgno>pPager->origDbSize );
assert( pPg->dirty );
assert( pPager->needSync );
}
/* Unlink pPg from it's hash-chain */
unlinkHashChain(pPager, pPg);
/* If the cache contains a page with page-number pgno, remove it
** from it's hash chain. Also, if the PgHdr.needSync was set for
** page pgno before the 'move' operation, it needs to be retained
** for the page moved there.
*/
pPg->needSync = 0;
pPgOld = pager_lookup(pPager, pgno);
if( pPgOld ){
assert( pPgOld->nRef==0 );
unlinkHashChain(pPager, pPgOld);
makeClean(pPgOld);
pPg->needSync = pPgOld->needSync;
}else{
pPg->needSync = 0;
}
if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
pPg->inJournal = (pPager->aInJournal[pgno/8] & (1<<(pgno&7)))!=0;
}else{
pPg->inJournal = 0;
assert( pPg->needSync==0 || (int)pgno>pPager->origDbSize );
}
/* Change the page number for pPg and insert it into the new hash-chain. */
assert( pgno!=0 );
pPg->pgno = pgno;
h = pgno & (pPager->nHash-1);
if( pPager->aHash[h] ){
assert( pPager->aHash[h]->pPrevHash==0 );
pPager->aHash[h]->pPrevHash = pPg;
}
pPg->pNextHash = pPager->aHash[h];
pPager->aHash[h] = pPg;
pPg->pPrevHash = 0;
makeDirty(pPg);
pPager->dirtyCache = 1;
if( needSyncPgno ){
/* If needSyncPgno is non-zero, then the journal file needs to be
** sync()ed before any data is written to database file page needSyncPgno.
** Currently, no such page exists in the page-cache and the
** Pager.aInJournal bit has been set. This needs to be remedied by loading
** the page into the pager-cache and setting the PgHdr.needSync flag.
**
** The sqlite3PagerGet() call may cause the journal to sync. So make
** sure the Pager.needSync flag is set too.
*/
int rc;
PgHdr *pPgHdr;
assert( pPager->needSync );
rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr);
if( rc!=SQLITE_OK ) return rc;
pPager->needSync = 1;
pPgHdr->needSync = 1;
pPgHdr->inJournal = 1;
makeDirty(pPgHdr);
sqlite3PagerUnref(pPgHdr);
}
return SQLITE_OK;
}
#endif
/*
** Return a pointer to the data for the specified page.
*/
void *sqlite3PagerGetData(DbPage *pPg){
return PGHDR_TO_DATA(pPg);
}
/*
** Return a pointer to the Pager.nExtra bytes of "extra" space
** allocated along with the specified page.
*/
void *sqlite3PagerGetExtra(DbPage *pPg){
Pager *pPager = pPg->pPager;
return (pPager?PGHDR_TO_EXTRA(pPg, pPager):0);
}
/*
** Get/set the locking-mode for this pager. Parameter eMode must be one
** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
** the locking-mode is set to the value specified.
**
** The returned value is either PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
** locking-mode.
*/
int sqlite3PagerLockingMode(Pager *pPager, int eMode){
assert( eMode==PAGER_LOCKINGMODE_QUERY
|| eMode==PAGER_LOCKINGMODE_NORMAL
|| eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_QUERY<0 );
assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
if( eMode>=0 && !pPager->tempFile ){
pPager->exclusiveMode = eMode;
}
return (int)pPager->exclusiveMode;
}
#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
/*
** Return the current state of the file lock for the given pager.
** The return value is one of NO_LOCK, SHARED_LOCK, RESERVED_LOCK,
** PENDING_LOCK, or EXCLUSIVE_LOCK.
*/
int sqlite3PagerLockstate(Pager *pPager){
return sqlite3OsLockState(pPager->fd);
}
#endif
#ifdef SQLITE_DEBUG
/*
** Print a listing of all referenced pages and their ref count.
*/
void sqlite3PagerRefdump(Pager *pPager){
PgHdr *pPg;
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
if( pPg->nRef<=0 ) continue;
sqlite3DebugPrintf("PAGE %3d addr=%p nRef=%d\n",
pPg->pgno, PGHDR_TO_DATA(pPg), pPg->nRef);
}
}
#endif
#endif /* SQLITE_OMIT_DISKIO */