/*
** 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 1.128 2004/06/15 11:40:09 danielk1977 Exp $
*/
#include "os.h" /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
/*
** Macros for troubleshooting. Normally turned off
*/
#if 0
static Pager *mainPager = 0;
#define SET_PAGER(X) if( mainPager==0 ) mainPager = (X)
#define CLR_PAGER(X) if( mainPager==(X) ) mainPager = 0
#define TRACE1(X) if( pPager==mainPager ) sqlite3DebugPrintf(X)
#define TRACE2(X,Y) if( pPager==mainPager ) sqlite3DebugPrintf(X,Y)
#define TRACE3(X,Y,Z) if( pPager==mainPager ) sqlite3DebugPrintf(X,Y,Z)
#else
#define SET_PAGER(X)
#define CLR_PAGER(X)
#define TRACE1(X)
#define TRACE2(X,Y)
#define TRACE3(X,Y,Z)
#endif
/*
** The page cache as a whole is always in one of the following
** states:
**
** PAGER_UNLOCK The page cache is not currently reading or
** writing the database file. There is no
** data held in memory. This is the initial
** state.
**
** PAGER_SHARED The page cache is reading the database.
** Writing is not permitted. There can be
** multiple readers accessing the same database
** file at the same time.
**
** PAGER_RESERVED This process has reserved the database for writing
** but has not yet made any changes. Only one process
** at a time can reserve the database. The original
** database file has not been modified so other
** processes may still be reading the on-disk
** database file.
**
** PAGER_EXCLUSIVE The page cache is writing the database.
** Access is exclusive. No other processes or
** threads can be reading or writing while one
** process is writing.
**
** PAGER_SYNCED The pager moves to this state from PAGER_EXCLUSIVE
** after all dirty pages have been written to the
** database file and the file has been synced to
** disk. All that remains to do is to remove the
** journal file and the transaction will be
** committed.
**
** The page cache comes up in PAGER_UNLOCK. The first time a
** sqlite3pager_get() occurs, the state transitions to PAGER_SHARED.
** After all pages have been released using sqlite_page_unref(),
** the state transitions back to PAGER_UNLOCK. The first time
** that sqlite3pager_write() is called, the state transitions to
** PAGER_RESERVED. (Note that sqlite_page_write() can only be
** called on an outstanding page which means that the pager must
** be in PAGER_SHARED before it transitions to PAGER_RESERVED.)
** The transition to PAGER_EXCLUSIVE occurs when before any changes
** are made to the database file. After an sqlite3pager_rollback()
** or sqlite_pager_commit(), the state goes back to PAGER_SHARED.
*/
#define PAGER_UNLOCK 0
#define PAGER_SHARED 1
#define PAGER_RESERVED 2
#define PAGER_EXCLUSIVE 3
#define PAGER_SYNCED 4
/*
** Each in-memory image of a page begins with the following header.
** This header is only visible to this pager module. The client
** code that calls pager sees only the data that follows the header.
**
** Client code should call sqlite3pager_write() on a page prior to making
** any modifications to that page. The first time sqlite3pager_write()
** is called, the original page contents are written into the rollback
** journal and PgHdr.inJournal and PgHdr.needSync are set. Later, once
** the journal page has made it onto the disk surface, PgHdr.needSync
** is cleared. The modified page cannot be written back into the original
** database file until the journal pages has been synced to disk and the
** PgHdr.needSync has been cleared.
**
** The PgHdr.dirty flag is set when sqlite3pager_write() is called and
** is cleared again when the page content is written back to the original
** database file.
*/
typedef struct PgHdr PgHdr;
struct PgHdr {
Pager *pPager; /* The pager to which this page belongs */
Pgno pgno; /* The page number for this page */
PgHdr *pNextHash, *pPrevHash; /* Hash collision chain for PgHdr.pgno */
PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */
PgHdr *pNextAll; /* A list of all pages */
PgHdr *pNextStmt, *pPrevStmt; /* List of pages in the statement journal */
u8 inJournal; /* TRUE if has been written to journal */
u8 inStmt; /* TRUE if in the statement subjournal */
u8 dirty; /* TRUE if we need to write back changes */
u8 needSync; /* Sync journal before writing this page */
u8 alwaysRollback; /* Disable dont_rollback() for this page */
short int nRef; /* Number of users of this page */
PgHdr *pDirty; /* Dirty pages sorted by PgHdr.pgno */
/* SQLITE_PAGE_SIZE bytes of page data follow this header */
/* Pager.nExtra bytes of local data follow the page data */
};
/*
** For an in-memory only database, some extra information is recorded about
** each page so that changes can be rolled back. (Journal files are not
** used for in-memory databases.) The following information is added to
** the end of every EXTRA block for in-memory databases.
**
** This information could have been added directly to the PgHdr structure.
** But then it would take up an extra 8 bytes of storage on every PgHdr
** even for disk-based databases. Splitting it out saves 8 bytes. This
** is only a savings of 0.8% but those percentages add up.
*/
typedef struct PgHistory PgHistory;
struct PgHistory {
u8 *pOrig; /* Original page text. Restore to this on a full rollback */
u8 *pStmt; /* Text as it was at the beginning of the current statement */
};
/*
** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC
# define CODEC(P,D,N,X) if( P->xCodec ){ P->xCodec(P->pCodecArg,D,N,X); }
#else
# define CODEC(P,D,N,X)
#endif
/*
** Convert a pointer to a PgHdr into a pointer to its data
** and back again.
*/
#define PGHDR_TO_DATA(P) ((void*)(&(P)[1]))
#define DATA_TO_PGHDR(D) (&((PgHdr*)(D))[-1])
#define PGHDR_TO_EXTRA(P) ((void*)&((char*)(&(P)[1]))[SQLITE_PAGE_SIZE])
#define PGHDR_TO_HIST(P,PGR) \
((PgHistory*)&((char*)(&(P)[1]))[(PGR)->pageSize+(PGR)->nExtra])
/*
** How big to make the hash table used for locating in-memory pages
** by page number.
*/
#define N_PG_HASH 2048
/*
** Hash a page number
*/
#define pager_hash(PN) ((PN)&(N_PG_HASH-1))
/*
** A open page cache is an instance of the following structure.
*/
struct Pager {
char *zFilename; /* Name of the database file */
char *zJournal; /* Name of the journal file */
char *zDirectory; /* Directory hold database and journal files */
OsFile fd, jfd; /* File descriptors for database and journal */
OsFile stfd; /* File descriptor for the statement subjournal*/
int dbSize; /* Number of pages in the file */
int origDbSize; /* dbSize before the current change */
int stmtSize; /* Size of database (in pages) at stmt_begin() */
off_t stmtJSize; /* Size of journal at stmt_begin() */
int nRec; /* Number of pages written to the journal */
u32 cksumInit; /* Quasi-random value added to every checksum */
int stmtNRec; /* Number of records in stmt subjournal */
int nExtra; /* Add this many bytes to each in-memory page */
void (*xDestructor)(void*,int); /* Call this routine when freeing pages */
void (*xReiniter)(void*,int); /* Call this routine when reloading pages */
int pageSize; /* Number of bytes in a page */
int nPage; /* Total number of in-memory pages */
int nRef; /* Number of in-memory pages with PgHdr.nRef>0 */
int mxPage; /* Maximum number of pages to hold in cache */
int nHit, nMiss, nOvfl; /* Cache hits, missing, and LRU overflows */
void (*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
void *pCodecArg; /* First argument to xCodec() */
u8 journalOpen; /* True if journal file descriptors is valid */
u8 journalStarted; /* True if header of journal is synced */
u8 useJournal; /* Use a rollback journal on this file */
u8 stmtOpen; /* True if the statement subjournal is open */
u8 stmtInUse; /* True we are in a statement subtransaction */
u8 stmtAutoopen; /* Open stmt journal when main journal is opened*/
u8 noSync; /* Do not sync the journal if true */
u8 fullSync; /* Do extra syncs of the journal for robustness */
u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */
u8 errMask; /* One of several kinds of errors */
u8 tempFile; /* zFilename is a temporary file */
u8 readOnly; /* True for a read-only database */
u8 needSync; /* True if an fsync() is needed on the journal */
u8 dirtyCache; /* True if cached pages have changed */
u8 alwaysRollback; /* Disable dont_rollback() for all pages */
u8 memDb; /* True to inhibit all file I/O */
u8 *aInJournal; /* One bit for each page in the database file */
u8 *aInStmt; /* One bit for each page in the database */
int nMaster; /* Number of bytes to reserve for master j.p */
BusyHandler *pBusyHandler; /* Pointer to sqlite.busyHandler */
PgHdr *pFirst, *pLast; /* List of free pages */
PgHdr *pFirstSynced; /* First free page with PgHdr.needSync==0 */
PgHdr *pAll; /* List of all pages */
PgHdr *pStmt; /* List of pages in the statement subjournal */
PgHdr *aHash[N_PG_HASH]; /* Hash table to map page number to PgHdr */
};
/*
** These are bits that can be set in Pager.errMask.
*/
#define PAGER_ERR_FULL 0x01 /* a write() failed */
#define PAGER_ERR_MEM 0x02 /* malloc() failed */
#define PAGER_ERR_LOCK 0x04 /* error in the locking protocol */
#define PAGER_ERR_CORRUPT 0x08 /* database or journal corruption */
#define PAGER_ERR_DISK 0x10 /* general disk I/O error - bad hard drive? */
/*
** Journal files begin with the following magic string. The data
** was obtained from /dev/random. It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
** checking information. If the power fails while the journal is begin
** written, semi-random garbage data might appear in the journal
** file after power is restored. If an attempt is then made
** to roll the journal back, the database could be corrupted. The additional
** sanity checking data is an attempt to discover the garbage in the
** journal and ignore it.
**
** The sanity checking information for the new journal format consists
** of a 32-bit checksum on each page of data. The checksum covers both
** the page number and the SQLITE_PAGE_SIZE bytes of data for the page.
** This cksum is initialized to a 32-bit random value that appears in the
** journal file right after the header. The random initializer is important,
** because garbage data that appears at the end of a journal is likely
** data that was once in other files that have now been deleted. If the
** garbage data came from an obsolete journal file, the checksums might
** be correct. But by initializing the checksum to random value which
** is different for every journal, we minimize that risk.
*/
static const unsigned char 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_HDR_SZ(pPager) (24 + (pPager)->nMaster)
#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8)
/*
** Enable reference count tracking (for debugging) here:
*/
#ifdef SQLITE_TEST
int pager3_refinfo_enable = 0;
static void pager_refinfo(PgHdr *p){
static int cnt = 0;
if( !pager3_refinfo_enable ) return;
printf(
"REFCNT: %4d addr=0x%08x nRef=%d\n",
p->pgno, (int)PGHDR_TO_DATA(p), p->nRef
);
cnt++; /* Something to set a breakpoint on */
}
# define REFINFO(X) pager_refinfo(X)
#else
# define REFINFO(X)
#endif
/*
** Read a 32-bit integer from the given file descriptor. Store the integer
** that is read in *pRes. Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
*/
static int read32bits(OsFile *fd, u32 *pRes){
u32 res;
int rc;
rc = sqlite3OsRead(fd, &res, sizeof(res));
if( rc==SQLITE_OK ){
unsigned char ac[4];
memcpy(ac, &res, 4);
res = (ac[0]<<24) | (ac[1]<<16) | (ac[2]<<8) | ac[3];
}
*pRes = res;
return rc;
}
/*
** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK
** on success or an error code is something goes wrong.
*/
static int write32bits(OsFile *fd, u32 val){
unsigned char ac[4];
ac[0] = (val>>24) & 0xff;
ac[1] = (val>>16) & 0xff;
ac[2] = (val>>8) & 0xff;
ac[3] = val & 0xff;
return sqlite3OsWrite(fd, ac, 4);
}
/*
** Write the 32-bit integer 'val' into the page identified by page header
** 'p' at offset 'offset'.
*/
static void store32bits(u32 val, PgHdr *p, int offset){
unsigned char *ac;
ac = &((unsigned char*)PGHDR_TO_DATA(p))[offset];
ac[0] = (val>>24) & 0xff;
ac[1] = (val>>16) & 0xff;
ac[2] = (val>>8) & 0xff;
ac[3] = val & 0xff;
}
/*
** Read a 32-bit integer at offset 'offset' from the page identified by
** page header 'p'.
*/
static u32 retrieve32bits(PgHdr *p, int offset){
unsigned char *ac;
ac = &((unsigned char*)PGHDR_TO_DATA(p))[offset];
return (ac[0]<<24) | (ac[1]<<16) | (ac[2]<<8) | ac[3];
}
/*
** Convert the bits in the pPager->errMask into an approprate
** return code.
*/
static int pager_errcode(Pager *pPager){
int rc = SQLITE_OK;
if( pPager->errMask & PAGER_ERR_LOCK ) rc = SQLITE_PROTOCOL;
if( pPager->errMask & PAGER_ERR_DISK ) rc = SQLITE_IOERR;
if( pPager->errMask & PAGER_ERR_FULL ) rc = SQLITE_FULL;
if( pPager->errMask & PAGER_ERR_MEM ) rc = SQLITE_NOMEM;
if( pPager->errMask & PAGER_ERR_CORRUPT ) rc = SQLITE_CORRUPT;
return rc;
}
/*
** Add or remove a page from the list of all pages that are in the
** statement journal.
**
** The Pager keeps a separate list of pages that are currently in
** the statement journal. This helps the sqlite3pager_stmt_commit()
** routine run MUCH faster for the common case where there are many
** pages in memory but only a few are in the statement journal.
*/
static void page_add_to_stmt_list(PgHdr *pPg){
Pager *pPager = pPg->pPager;
if( pPg->inStmt ) return;
assert( pPg->pPrevStmt==0 && pPg->pNextStmt==0 );
pPg->pPrevStmt = 0;
if( pPager->pStmt ){
pPager->pStmt->pPrevStmt = pPg;
}
pPg->pNextStmt = pPager->pStmt;
pPager->pStmt = pPg;
pPg->inStmt = 1;
}
static void page_remove_from_stmt_list(PgHdr *pPg){
if( !pPg->inStmt ) return;
if( pPg->pPrevStmt ){
assert( pPg->pPrevStmt->pNextStmt==pPg );
pPg->pPrevStmt->pNextStmt = pPg->pNextStmt;
}else{
assert( pPg->pPager->pStmt==pPg );
pPg->pPager->pStmt = pPg->pNextStmt;
}
if( pPg->pNextStmt ){
assert( pPg->pNextStmt->pPrevStmt==pPg );
pPg->pNextStmt->pPrevStmt = pPg->pPrevStmt;
}
pPg->pNextStmt = 0;
pPg->pPrevStmt = 0;
pPg->inStmt = 0;
}
/*
** Find a page in the hash table given its page number. Return
** a pointer to the page or NULL if not found.
*/
static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
PgHdr *p = pPager->aHash[pager_hash(pgno)];
while( p && p->pgno!=pgno ){
p = p->pNextHash;
}
return p;
}
/*
** Unlock the database and clear the in-memory cache. This routine
** sets the state of the pager back to what it was when it was first
** opened. Any outstanding pages are invalidated and subsequent attempts
** to access those pages will likely result in a coredump.
*/
static void pager_reset(Pager *pPager){
PgHdr *pPg, *pNext;
for(pPg=pPager->pAll; pPg; pPg=pNext){
pNext = pPg->pNextAll;
sqliteFree(pPg);
}
pPager->pFirst = 0;
pPager->pFirstSynced = 0;
pPager->pLast = 0;
pPager->pAll = 0;
memset(pPager->aHash, 0, sizeof(pPager->aHash));
pPager->nPage = 0;
if( pPager->state>=PAGER_RESERVED ){
sqlite3pager_rollback(pPager);
}
sqlite3OsUnlock(&pPager->fd, NO_LOCK);
pPager->state = PAGER_UNLOCK;
pPager->dbSize = -1;
pPager->nRef = 0;
assert( pPager->journalOpen==0 );
}
/*
** When this routine is called, the pager has the journal file open and
** a RESERVED or EXCLUSIVE lock on the database. This routine releases
** the database lock and acquires a SHARED lock in its place. The journal
** file is deleted and closed.
**
** TODO: Consider keeping the journal file open for temporary databases.
** This might give a performance improvement on windows where opening
** a file is an expensive operation.
*/
static int pager_unwritelock(Pager *pPager){
PgHdr *pPg;
if( pPager->state<PAGER_RESERVED ){
return SQLITE_OK;
}
sqlite3pager_stmt_commit(pPager);
if( pPager->stmtOpen ){
sqlite3OsClose(&pPager->stfd);
pPager->stmtOpen = 0;
}
if( pPager->journalOpen ){
sqlite3OsClose(&pPager->jfd);
pPager->journalOpen = 0;
sqlite3OsDelete(pPager->zJournal);
sqliteFree( pPager->aInJournal );
pPager->aInJournal = 0;
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
pPg->inJournal = 0;
pPg->dirty = 0;
pPg->needSync = 0;
}
}else{
assert( pPager->dirtyCache==0 || pPager->useJournal==0 );
}
sqlite3OsUnlock(&pPager->fd, SHARED_LOCK);
pPager->state = PAGER_SHARED;
return SQLITE_OK;
}
/*
** Compute and return a checksum for the page of data.
**
** This is not a real checksum. It is really just the sum of the
** random initial value and the page number. We experimented with
** a checksum of the entire data, but that was found to be too slow.
**
** Note that the page number is stored at the beginning of data and
** the checksum is stored at the end. This is important. If journal
** corruption occurs due to a power failure, the most likely scenario
** is that one end or the other of the record will be changed. It is
** much less likely that the two ends of the journal record will be
** correct and the middle be corrupt. Thus, this "checksum" scheme,
** though fast and simple, catches the mostly likely kind of corruption.
**
** FIX ME: Consider adding every 200th (or so) byte of the data to the
** checksum. That way if a single page spans 3 or more disk sectors and
** only the middle sector is corrupt, we will still have a reasonable
** chance of failing the checksum and thus detecting the problem.
*/
static u32 pager_cksum(Pager *pPager, Pgno pgno, const char *aData){
u32 cksum = pPager->cksumInit + pgno;
return cksum;
}
/*
** Read a single page from the journal file opened on file descriptor
** jfd. Playback this one page.
**
** If useCksum==0 it means this journal does not use checksums. Checksums
** are not used in statement journals because statement journals do not
** need to survive power failures.
*/
static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int useCksum){
int rc;
PgHdr *pPg; /* An existing page in the cache */
Pgno pgno; /* The page number of a page in journal */
u32 cksum; /* Checksum used for sanity checking */
u8 aData[SQLITE_PAGE_SIZE]; /* Store data here */
rc = read32bits(jfd, &pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(jfd, &aData, pPager->pageSize);
if( rc!=SQLITE_OK ) return rc;
/* Sanity checking on the page. This is more important that I originally
** thought. If a power failure occurs while the journal is being written,
** it could cause invalid data to be written into the journal. We need to
** detect this invalid data (with high probability) and ignore it.
*/
if( pgno==0 ){
return SQLITE_DONE;
}
if( pgno>(unsigned)pPager->dbSize ){
return SQLITE_OK;
}
if( useCksum ){
rc = read32bits(jfd, &cksum);
if( rc ) return rc;
if( pager_cksum(pPager, pgno, aData)!=cksum ){
return SQLITE_DONE;
}
}
assert( pPager->state==PAGER_RESERVED || pPager->state>=PAGER_EXCLUSIVE );
/* If the pager is in RESERVED state, then there must be a copy of this
** page in the pager cache. In this case just update the pager cache,
** not the database file. The page is left marked dirty in this case.
**
** FIX ME: Ideally the page would only be left marked dirty when the
** pager is in RESERVED state if it was dirty when this statement
** transaction was started.
**
** If in EXCLUSIVE state, then we update the pager cache if it exists
** and the main file. The page is then marked not dirty.
*/
pPg = pager_lookup(pPager, pgno);
assert( pPager->state>=PAGER_EXCLUSIVE || pPg );
TRACE2("PLAYBACK page %d\n", pgno);
if( pPager->state>=PAGER_EXCLUSIVE ){
sqlite3OsSeek(&pPager->fd, (pgno-1)*(off_t)SQLITE_PAGE_SIZE);
rc = sqlite3OsWrite(&pPager->fd, aData, SQLITE_PAGE_SIZE);
}
if( pPg ){
/* No page should ever be rolled back that is in use, except for page
** 1 which is held in use in order to keep the lock on the database
** active.
*/
void *pData;
assert( pPg->nRef==0 || pPg->pgno==1 );
pData = PGHDR_TO_DATA(pPg);
memcpy(pData, aData, pPager->pageSize);
if( pPager->xDestructor ){ /*** FIX ME: Should this be xReinit? ***/
pPager->xDestructor(pData, pPager->pageSize);
}
if( pPager->state>=PAGER_EXCLUSIVE ){
pPg->dirty = 0;
pPg->needSync = 0;
}
CODEC(pPager, pData, pPg->pgno, 3);
}
return rc;
}
/*
** Parameter zMaster is the name of a master journal file. A single journal
** file that referred to the master journal file has just been rolled back.
** This routine checks if it is possible to delete the master journal file,
** and does so if it is.
**
** The master journal file contains the names of all child journals.
** To tell if a master journal can be deleted, check to each of the
** children. If all children are either missing or do not refer to
** a different master journal, then this master journal can be deleted.
*/
static int pager_delmaster(const char *zMaster){
int rc;
int master_open = 0;
OsFile master;
char *zMasterJournal = 0; /* Contents of master journal file */
off_t nMasterJournal; /* Size of master journal file */
/* Open the master journal file exclusively in case some other process
** is running this routine also. Not that it makes too much difference.
*/
rc = sqlite3OsOpenExclusive(zMaster, &master, 0);
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;
int nMasterPtr; /* Number of bytes allocated at zMasterPtr */
/* Load the entire master journal file into space obtained from
** sqliteMalloc() and pointed to by zMasterJournal.
**
** Also allocate an extra (strlen(zMaster)+1) bytes. This space is used
** to load a master-journal filename from some other journal file to
** check if it points at this master journal file.
*/
nMasterPtr = strlen(zMaster) + 1;
zMasterJournal = (char *)sqliteMalloc(nMasterJournal) + nMasterPtr;
if( !zMasterJournal ){
rc = SQLITE_NOMEM;
goto delmaster_out;
}
zMasterPtr = &zMasterJournal[nMasterJournal];
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;
int nMaster;
off_t jsz;
rc = sqlite3OsOpenReadOnly(zJournal, &journal);
if( rc!=SQLITE_OK ){
sqlite3OsClose(&journal);
goto delmaster_out;
}
/* Check if the file is big enough to be a journal file
** with the required master journal name. If not, ignore it.
*/
rc = sqlite3OsFileSize(&journal, &jsz);
if( rc!=SQLITE_OK ){
sqlite3OsClose(&journal);
goto delmaster_out;
}
if( jsz<(25+strlen(zMaster)) ){
sqlite3OsClose(&journal);
continue;
}
/* Seek to the point in the journal where the master journal name
** is stored. Read the master journal name into memory obtained
** from malloc.
*/
rc = sqlite3OsSeek(&journal, 20);
if( rc!=SQLITE_OK ) goto delmaster_out;
rc = read32bits(&journal, (u32*)&nMaster);
if( rc!=SQLITE_OK ) goto delmaster_out;
if( nMaster>=nMasterPtr ){
rc = sqlite3OsRead(&journal, zMasterPtr, nMasterPtr);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
if( zMasterPtr[nMasterPtr-1]=='\0' && !strcmp(zMasterPtr, zMaster) ){
/* We have a match. Do not delete the master journal file. */
goto delmaster_out;
}
}
}
zJournal += (strlen(zJournal)+1);
}
}
sqlite3OsDelete(zMaster);
delmaster_out:
if( zMasterJournal ){
sqliteFree(zMasterJournal);
}
if( master_open ){
sqlite3OsClose(&master);
}
return rc;
}
/*
** Make every page in the cache agree with what is on disk. In other words,
** reread the disk to reset the state of the cache.
**
** This routine is called after a rollback in which some of the dirty cache
** pages had never been written out to disk. We need to roll back the
** cache content and the easiest way to do that is to reread the old content
** back from the disk.
*/
static int pager_reload_cache(Pager *pPager){
PgHdr *pPg;
int rc = SQLITE_OK;
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
char zBuf[SQLITE_PAGE_SIZE];
if( !pPg->dirty ) continue;
if( (int)pPg->pgno <= pPager->origDbSize ){
sqlite3OsSeek(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)(pPg->pgno-1));
rc = sqlite3OsRead(&pPager->fd, zBuf, SQLITE_PAGE_SIZE);
TRACE2("REFETCH page %d\n", pPg->pgno);
CODEC(pPager, zBuf, pPg->pgno, 2);
if( rc ) break;
}else{
memset(zBuf, 0, SQLITE_PAGE_SIZE);
}
if( pPg->nRef==0 || memcmp(zBuf, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE) ){
memcpy(PGHDR_TO_DATA(pPg), zBuf, SQLITE_PAGE_SIZE);
if( pPager->xReiniter ){
pPager->xReiniter(PGHDR_TO_DATA(pPg), pPager->pageSize);
}else{
memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
}
}
pPg->needSync = 0;
pPg->dirty = 0;
}
return rc;
}
/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.
**
** The journal file format is as follows:
**
** (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 the database will likely already be
** corrupted, so the PAGER_ERR_CORRUPT bit is set in pPager->errMask
** and SQLITE_CORRUPT is returned. If it all works, then this routine
** returns SQLITE_OK.
*/
static int pager_playback(Pager *pPager, int useJournalSize){
off_t szJ; /* Size of the journal file in bytes */
int nRec; /* Number of Records in the journal */
int i; /* Loop counter */
Pgno mxPg = 0; /* Size of the original file in pages */
unsigned char aMagic[8]; /* A buffer to hold the magic header */
int rc; /* Result code of a subroutine */
int nMaster; /* Number of bytes in the name of master journal */
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 );
sqlite3OsSeek(&pPager->jfd, 0);
rc = sqlite3OsFileSize(&pPager->jfd, &szJ);
if( rc!=SQLITE_OK ){
goto end_playback;
}
/* If the journal file is too small to contain a complete header,
** it must mean that the process that created the journal was just
** beginning to write the journal file when it died. In that case,
** the database file should have still been completely unchanged.
** Nothing needs to be rolled back. We can safely ignore this journal.
*/
if( szJ < 24 ){
goto end_playback;
}
/* (1) Read the beginning of the journal and verify the magic string
** at the beginning of the journal. */
rc = sqlite3OsRead(&pPager->jfd, aMagic, sizeof(aMagic));
if( rc!=SQLITE_OK || memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
rc = SQLITE_PROTOCOL;
goto end_playback;
}
/* (2) Read the number of pages stored in the journal. */
rc = read32bits(&pPager->jfd, (u32*)&nRec);
if( rc ) goto end_playback;
if( nRec==0xffffffff || useJournalSize ){
nRec = (szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager);
}
/* (3) Read the initial value for the sanity checksum */
rc = read32bits(&pPager->jfd, &pPager->cksumInit);
if( rc ) goto end_playback;
/* (4) Read the number of pages in the database file prior to the
** start of the transaction */
rc = read32bits(&pPager->jfd, &mxPg);
if( rc!=SQLITE_OK ){
goto end_playback;
}
/* (5) and (6): Check if a master journal file is specified. If one is
** specified, only proceed with the playback if it still exists. */
rc = read32bits(&pPager->jfd, &nMaster);
if( rc ) goto end_playback;
if( nMaster>0 ){
zMaster = sqliteMalloc(nMaster);
if( !zMaster ){
rc = SQLITE_NOMEM;
goto end_playback;
}
rc = sqlite3OsRead(&pPager->jfd, zMaster, nMaster);
if( rc!=SQLITE_OK || (zMaster[0] && !sqlite3OsFileExists(zMaster)) ){
goto end_playback;
}
}
/* Truncate the database file back to it's original size */
assert( pPager->origDbSize==0 || pPager->origDbSize==mxPg );
rc = sqlite3OsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)mxPg);
if( rc!=SQLITE_OK ){
goto end_playback;
}
pPager->dbSize = mxPg;
/* Copy original pages out of the journal and back into the database file.
*/
for(i=0; i<nRec; i++){
rc = pager_playback_one_page(pPager, &pPager->jfd, 1);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
}
break;
}
}
/* Pages that have been written to the journal but never synced
** where not restored by the loop above. We have to restore those
** pages by reading them back from the original database.
*/
if( rc==SQLITE_OK ){
pager_reload_cache(pPager);
}
end_playback:
if( zMaster ){
/* If there was a master journal and this routine will return true,
** see if it is possible to delete the master journal. If errors
** occur during this process, ignore them.
*/
if( rc==SQLITE_OK ){
pager_delmaster(zMaster);
}
sqliteFree(zMaster);
}
if( rc!=SQLITE_OK ){
/* FIX ME: We shouldn't delete the journal if an error occured during
** rollback. It may have been a transient error and the rollback may
** succeed next time it is attempted.
*/
pager_unwritelock(pPager);
pPager->errMask |= PAGER_ERR_CORRUPT;
rc = SQLITE_CORRUPT;
}else{
rc = pager_unwritelock(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){
off_t szJ; /* Size of the full journal */
int nRec; /* Number of Records */
int i; /* Loop counter */
int rc;
/* Truncate the database back to its original size.
*/
rc = sqlite3OsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)pPager->stmtSize);
pPager->dbSize = pPager->stmtSize;
/* Figure out how many records are in the statement journal.
*/
assert( pPager->stmtInUse && pPager->journalOpen );
sqlite3OsSeek(&pPager->stfd, 0);
nRec = pPager->stmtNRec;
/* Copy original pages out of the statement journal and back into the
** database file. Note that the statement journal omits checksums from
** each record since power-failure recovery is not important to statement
** journals.
*/
for(i=nRec-1; i>=0; i--){
rc = pager_playback_one_page(pPager, &pPager->stfd, 0);
assert( rc!=SQLITE_DONE );
if( rc!=SQLITE_OK ) goto end_stmt_playback;
}
/* Figure out how many pages need to be copied out of the transaction
** journal.
*/
rc = sqlite3OsSeek(&pPager->jfd, pPager->stmtJSize);
if( rc!=SQLITE_OK ){
goto end_stmt_playback;
}
rc = sqlite3OsFileSize(&pPager->jfd, &szJ);
if( rc!=SQLITE_OK ){
goto end_stmt_playback;
}
nRec = (szJ - pPager->stmtJSize)/JOURNAL_PG_SZ(pPager);
for(i=nRec-1; i>=0; i--){
rc = pager_playback_one_page(pPager, &pPager->jfd, 1);
if( rc!=SQLITE_OK ){
assert( rc!=SQLITE_DONE );
goto end_stmt_playback;
}
}
end_stmt_playback:
if( rc!=SQLITE_OK ){
pPager->errMask |= PAGER_ERR_CORRUPT;
rc = SQLITE_CORRUPT;
}
return rc;
}
/*
** Change the maximum number of in-memory pages that are allowed.
**
** The maximum number is the absolute value of the mxPage parameter.
** If mxPage is negative, the noSync flag is also set. noSync bypasses
** calls to sqlite3OsSync(). The pager runs much faster with noSync on,
** but if the operating system crashes or there is an abrupt power
** failure, the database file might be left in an inconsistent and
** unrepairable state.
*/
void sqlite3pager_set_cachesize(Pager *pPager, int mxPage){
if( mxPage>=0 ){
pPager->noSync = pPager->tempFile;
if( pPager->noSync ) pPager->needSync = 0;
}else{
pPager->noSync = 1;
mxPage = -mxPage;
}
if( mxPage>10 ){
pPager->mxPage = mxPage;
}
}
/*
** Adjust the robustness of the database to damage due to OS crashes
** or power failures by changing the number of syncs()s when writing
** the rollback journal. There are three levels:
**
** OFF sqlite3OsSync() is never called. This is the default
** for temporary and transient files.
**
** NORMAL The journal is synced once before writes begin on the
** database. This is normally adequate protection, but
** it is theoretically possible, though very unlikely,
** that an inopertune power failure could leave the journal
** in a state which would cause damage to the database
** when it is rolled back.
**
** FULL The journal is synced twice before writes begin on the
** database (with some additional information - the nRec field
** of the journal header - being written in between the two
** syncs). If we assume that writing a
** single disk sector is atomic, then this mode provides
** assurance that the journal will not be corrupted to the
** point of causing damage to the database during rollback.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
void sqlite3pager_set_safety_level(Pager *pPager, int level){
pPager->noSync = level==1 || pPager->tempFile;
pPager->fullSync = level==3 && !pPager->tempFile;
if( pPager->noSync ) pPager->needSync = 0;
}
/*
** Open a temporary file. Write the name of the file into zName
** (zName must be at least SQLITE_TEMPNAME_SIZE bytes long.) Write
** the file descriptor into *fd. Return SQLITE_OK on success or some
** other error code if we fail.
**
** The OS will automatically delete the temporary file when it is
** closed.
*/
static int sqlite3pager_opentemp(char *zFile, OsFile *fd){
int cnt = 8;
int rc;
do{
cnt--;
sqlite3OsTempFileName(zFile);
rc = sqlite3OsOpenExclusive(zFile, fd, 1);
}while( cnt>0 && rc!=SQLITE_OK );
return rc;
}
/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist. The file is not locked until
** the first call to sqlite3pager_get() and is only held open until the
** last page is released using sqlite3pager_unref().
**
** If zFilename is NULL then a randomly-named temporary file is created
** and used as the file to be cached. The file will be deleted
** automatically when it is closed.
*/
int sqlite3pager_open(
Pager **ppPager, /* Return the Pager structure here */
const char *zFilename, /* Name of the database file to open */
int mxPage, /* Max number of in-memory cache pages */
int nExtra, /* Extra bytes append to each in-memory page */
int useJournal, /* TRUE to use a rollback journal on this file */
void *pBusyHandler /* Busy callback */
){
Pager *pPager;
char *zFullPathname;
int nameLen;
OsFile fd;
int rc, i;
int tempFile;
int memDb = 0;
int readOnly = 0;
char zTemp[SQLITE_TEMPNAME_SIZE];
*ppPager = 0;
if( sqlite3_malloc_failed ){
return SQLITE_NOMEM;
}
if( zFilename && zFilename[0] ){
if( strcmp(zFilename,":memory:")==0 ){
memDb = 1;
zFullPathname = sqliteMalloc(4);
if( zFullPathname ) strcpy(zFullPathname, "");
rc = SQLITE_OK;
}else{
zFullPathname = sqlite3OsFullPathname(zFilename);
rc = sqlite3OsOpenReadWrite(zFullPathname, &fd, &readOnly);
tempFile = 0;
}
}else{
rc = sqlite3pager_opentemp(zTemp, &fd);
zFilename = zTemp;
zFullPathname = sqlite3OsFullPathname(zFilename);
tempFile = 1;
}
if( sqlite3_malloc_failed ){
return SQLITE_NOMEM;
}
if( rc!=SQLITE_OK ){
sqliteFree(zFullPathname);
return SQLITE_CANTOPEN;
}
nameLen = strlen(zFullPathname);
pPager = sqliteMalloc( sizeof(*pPager) + nameLen*3 + 30 );
if( pPager==0 ){
sqlite3OsClose(&fd);
sqliteFree(zFullPathname);
return SQLITE_NOMEM;
}
SET_PAGER(pPager);
pPager->zFilename = (char*)&pPager[1];
pPager->zDirectory = &pPager->zFilename[nameLen+1];
pPager->zJournal = &pPager->zDirectory[nameLen+1];
strcpy(pPager->zFilename, zFullPathname);
strcpy(pPager->zDirectory, zFullPathname);
for(i=nameLen; i>0 && pPager->zDirectory[i-1]!='/'; i--){}
if( i>0 ) pPager->zDirectory[i-1] = 0;
strcpy(pPager->zJournal, zFullPathname);
sqliteFree(zFullPathname);
strcpy(&pPager->zJournal[nameLen], "-journal");
pPager->fd = fd;
pPager->journalOpen = 0;
pPager->useJournal = useJournal && !memDb;
pPager->stmtOpen = 0;
pPager->stmtInUse = 0;
pPager->nRef = 0;
pPager->dbSize = memDb-1;
pPager->pageSize = SQLITE_PAGE_SIZE;
pPager->stmtSize = 0;
pPager->stmtJSize = 0;
pPager->nPage = 0;
pPager->mxPage = mxPage>5 ? mxPage : 10;
pPager->state = PAGER_UNLOCK;
pPager->errMask = 0;
pPager->tempFile = tempFile;
pPager->memDb = memDb;
pPager->readOnly = readOnly;
pPager->needSync = 0;
pPager->noSync = pPager->tempFile || !useJournal;
pPager->pFirst = 0;
pPager->pFirstSynced = 0;
pPager->pLast = 0;
pPager->nExtra = nExtra;
pPager->pBusyHandler = (BusyHandler *)pBusyHandler;
memset(pPager->aHash, 0, sizeof(pPager->aHash));
*ppPager = pPager;
return SQLITE_OK;
}
/*
** Set the destructor for this pager. If not NULL, the destructor is called
** when the reference count on each page reaches zero. The destructor can
** be used to clean up information in the extra segment appended to each page.
**
** The destructor is not called as a result sqlite3pager_close().
** Destructors are only called by sqlite3pager_unref().
*/
void sqlite3pager_set_destructor(Pager *pPager, void (*xDesc)(void*,int)){
pPager->xDestructor = xDesc;
}
/*
** Set the reinitializer for this pager. If not NULL, the reinitializer
** is called when the content of a page in cache is restored to its original
** value as a result of a rollback. The callback gives higher-level code
** an opportunity to restore the EXTRA section to agree with the restored
** page data.
*/
void sqlite3pager_set_reiniter(Pager *pPager, void (*xReinit)(void*,int)){
pPager->xReiniter = xReinit;
}
/*
** Return the total number of pages in the disk file associated with
** pPager.
*/
int sqlite3pager_pagecount(Pager *pPager){
off_t n;
assert( pPager!=0 );
if( pPager->dbSize>=0 ){
return pPager->dbSize;
}
if( sqlite3OsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
pPager->errMask |= PAGER_ERR_DISK;
return 0;
}
n /= SQLITE_PAGE_SIZE;
if( !pPager->memDb && n==PENDING_BYTE/SQLITE_PAGE_SIZE ){
n++;
}
if( pPager->state!=PAGER_UNLOCK ){
pPager->dbSize = n;
}
return n;
}
/*
** Forward declaration
*/
static int syncJournal(Pager*, const char*);
/*
** Unlink a page from the free list (the list of all pages where nRef==0)
** and from its hash collision chain.
*/
static void unlinkPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
/* Keep the pFirstSynced pointer pointing at the first synchronized page */
if( pPg==pPager->pFirstSynced ){
PgHdr *p = pPg->pNextFree;
while( p && p->needSync ){ p = p->pNextFree; }
pPager->pFirstSynced = p;
}
/* Unlink from the freelist */
if( pPg->pPrevFree ){
pPg->pPrevFree->pNextFree = pPg->pNextFree;
}else{
assert( pPager->pFirst==pPg );
pPager->pFirst = pPg->pNextFree;
}
if( pPg->pNextFree ){
pPg->pNextFree->pPrevFree = pPg->pPrevFree;
}else{
assert( pPager->pLast==pPg );
pPager->pLast = pPg->pPrevFree;
}
pPg->pNextFree = pPg->pPrevFree = 0;
/* Unlink from the pgno hash table */
if( pPg->pNextHash ){
pPg->pNextHash->pPrevHash = pPg->pPrevHash;
}
if( pPg->pPrevHash ){
pPg->pPrevHash->pNextHash = pPg->pNextHash;
}else{
int h = pager_hash(pPg->pgno);
assert( pPager->aHash[h]==pPg );
pPager->aHash[h] = pPg->pNextHash;
}
pPg->pNextHash = pPg->pPrevHash = 0;
}
/*
** This routine is used to truncate an in-memory database. Delete
** all pages whose pgno is larger than pPager->dbSize and is unreferenced.
** Referenced pages larger than pPager->dbSize are zeroed.
*/
static void memoryTruncate(Pager *pPager){
PgHdr *pPg;
PgHdr **ppPg;
int dbSize = pPager->dbSize;
ppPg = &pPager->pAll;
while( (pPg = *ppPg)!=0 ){
if( pPg->pgno<=dbSize ){
ppPg = &pPg->pNextAll;
}else if( pPg->nRef>0 ){
memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
ppPg = &pPg->pNextAll;
}else{
*ppPg = pPg->pNextAll;
unlinkPage(pPg);
sqliteFree(pPg);
pPager->nPage--;
}
}
}
/*
** Truncate the file to the number of pages specified.
*/
int sqlite3pager_truncate(Pager *pPager, Pgno nPage){
int rc;
if( pPager->dbSize<0 ){
sqlite3pager_pagecount(pPager);
}
if( pPager->errMask!=0 ){
rc = pager_errcode(pPager);
return rc;
}
if( nPage>=(unsigned)pPager->dbSize ){
return SQLITE_OK;
}
if( pPager->memDb ){
pPager->dbSize = nPage;
memoryTruncate(pPager);
return SQLITE_OK;
}
rc = syncJournal(pPager, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3OsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)nPage);
if( rc==SQLITE_OK ){
pPager->dbSize = nPage;
}
return rc;
}
/*
** Shutdown the page cache. Free all memory and close all files.
**
** If a transaction was in progress when this routine is called, that
** transaction is rolled back. All outstanding pages are invalidated
** and their memory is freed. Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
*/
int sqlite3pager_close(Pager *pPager){
PgHdr *pPg, *pNext;
switch( pPager->state ){
case PAGER_RESERVED:
case PAGER_SYNCED:
case PAGER_EXCLUSIVE: {
sqlite3pager_rollback(pPager);
if( !pPager->memDb ){
sqlite3OsUnlock(&pPager->fd, NO_LOCK);
}
assert( pPager->journalOpen==0 );
break;
}
case PAGER_SHARED: {
if( !pPager->memDb ){
sqlite3OsUnlock(&pPager->fd, NO_LOCK);
}
break;
}
default: {
/* Do nothing */
break;
}
}
for(pPg=pPager->pAll; pPg; pPg=pNext){
pNext = pPg->pNextAll;
sqliteFree(pPg);
}
if( !pPager->memDb ){
sqlite3OsClose(&pPager->fd);
}
assert( pPager->journalOpen==0 );
/* Temp files are automatically deleted by the OS
** if( pPager->tempFile ){
** sqlite3OsDelete(pPager->zFilename);
** }
*/
CLR_PAGER(pPager);
if( pPager->zFilename!=(char*)&pPager[1] ){
assert( 0 ); /* Cannot happen */
sqliteFree(pPager->zFilename);
sqliteFree(pPager->zJournal);
sqliteFree(pPager->zDirectory);
}
sqliteFree(pPager);
return SQLITE_OK;
}
/*
** Return the page number for the given page data.
*/
Pgno sqlite3pager_pagenumber(void *pData){
PgHdr *p = DATA_TO_PGHDR(pData);
return p->pgno;
}
/*
** The page_ref() function increments the reference count for a page.
** If the page is currently on the freelist (the reference count is zero) then
** remove it from the freelist.
**
** For non-test systems, page_ref() is a macro that calls _page_ref()
** online of the reference count is zero. For test systems, page_ref()
** is a real function so that we can set breakpoints and trace it.
*/
static void _page_ref(PgHdr *pPg){
if( pPg->nRef==0 ){
/* The page is currently on the freelist. Remove it. */
if( pPg==pPg->pPager->pFirstSynced ){
PgHdr *p = pPg->pNextFree;
while( p && p->needSync ){ p = p->pNextFree; }
pPg->pPager->pFirstSynced = p;
}
if( pPg->pPrevFree ){
pPg->pPrevFree->pNextFree = pPg->pNextFree;
}else{
pPg->pPager->pFirst = pPg->pNextFree;
}
if( pPg->pNextFree ){
pPg->pNextFree->pPrevFree = pPg->pPrevFree;
}else{
pPg->pPager->pLast = pPg->pPrevFree;
}
pPg->pPager->nRef++;
}
pPg->nRef++;
REFINFO(pPg);
}
#ifdef SQLITE_TEST
static void page_ref(PgHdr *pPg){
if( pPg->nRef==0 ){
_page_ref(pPg);
}else{
pPg->nRef++;
REFINFO(pPg);
}
}
#else
# define page_ref(P) ((P)->nRef==0?_page_ref(P):(void)(P)->nRef++)
#endif
/*
** Increment the reference count for a page. The input pointer is
** a reference to the page data.
*/
int sqlite3pager_ref(void *pData){
PgHdr *pPg = DATA_TO_PGHDR(pData);
page_ref(pPg);
return SQLITE_OK;
}
/*
** Sync the journal. In other words, make sure all the pages that have
** been written to the journal have actually reached the surface of the
** disk. It is not safe to modify the original database file until after
** the journal has been synced. If the original database is modified before
** the journal is synced and a power failure occurs, the unsynced journal
** data would be lost and we would be unable to completely rollback the
** database changes. Database corruption would occur.
**
** This routine also updates the nRec field in the header of the journal.
** (See comments on the pager_playback() routine for additional information.)
** If the sync mode is FULL, two syncs will occur. First the whole journal
** is synced, then the nRec field is updated, then a second sync occurs.
**
** For temporary databases, we do not care if we are able to rollback
** after a power failure, so sync occurs.
**
** This routine clears the needSync field of every page current held in
** memory.
*/
static int syncJournal(Pager *pPager, const char *zMaster){
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 || zMaster ){
if( !pPager->tempFile ){
assert( pPager->journalOpen );
/* assert( !pPager->noSync ); // noSync might be set if synchronous
** was turned off after the transaction was started. Ticket #615 */
#ifndef NDEBUG
{
/* Make sure the pPager->nRec counter we are keeping agrees
** with the nRec computed from the size of the journal file.
*/
off_t hdrSz, pgSz, jSz;
hdrSz = JOURNAL_HDR_SZ(pPager);
pgSz = JOURNAL_PG_SZ(pPager);
rc = sqlite3OsFileSize(&pPager->jfd, &jSz);
if( rc!=0 ) return rc;
assert( pPager->nRec*pgSz+hdrSz==jSz );
}
#endif
{
/* Write the nRec value into the journal file header */
off_t szJ;
if( pPager->fullSync ){
TRACE2("SYNC journal of %d\n", pPager->fd.h);
rc = sqlite3OsSync(&pPager->jfd);
if( rc!=0 ) return rc;
}
sqlite3OsSeek(&pPager->jfd, sizeof(aJournalMagic));
rc = write32bits(&pPager->jfd, pPager->nRec);
if( rc ) return rc;
/* Write the name of the master journal file if one is specified */
if( zMaster ){
assert( strlen(zMaster)<pPager->nMaster );
rc = sqlite3OsSeek(&pPager->jfd, 20);
if( rc ) return rc;
rc = sqlite3OsWrite(&pPager->jfd, zMaster, strlen(zMaster)+1);
if( rc ) return rc;
}
szJ = JOURNAL_HDR_SZ(pPager) + pPager->nRec*JOURNAL_PG_SZ(pPager);
sqlite3OsSeek(&pPager->jfd, szJ);
}
TRACE2("SYNC journal of %d\n", pPager->fd.h);
rc = sqlite3OsSync(&pPager->jfd);
if( rc!=0 ) return rc;
pPager->journalStarted = 1;
}
pPager->needSync = 0;
/* Erase the needSync flag from every page.
*/
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
pPg->needSync = 0;
}
pPager->pFirstSynced = pPager->pFirst;
}
#ifndef NDEBUG
/* If the Pager.needSync flag is clear then the PgHdr.needSync
** flag must also be clear for all pages. Verify that this
** invariant is true.
*/
else{
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
assert( pPg->needSync==0 );
}
assert( pPager->pFirstSynced==pPager->pFirst );
}
#endif
return rc;
}
/*
** Given a list of pages (connected by the PgHdr.pDirty pointer) write
** every one of those pages out to the database file and mark them all
** as clean.
*/
static int pager_write_pagelist(PgHdr *pList){
Pager *pPager;
int rc;
int busy = 1;
if( pList==0 ) return SQLITE_OK;
pPager = pList->pPager;
/* At this point there may be either a RESERVED or EXCLUSIVE lock on the
** database file. If there is already an EXCLUSIVE lock, the following
** calls to sqlite3OsLock() are no-ops.
**
** Moving the lock from RESERVED to EXCLUSIVE actually involves going
** through an intermediate state PENDING. A PENDING lock prevents new
** readers from attaching to the database but is unsufficient for us to
** write. The idea of a PENDING lock is to prevent new readers from
** coming in while we wait for existing readers to clear.
**
** While the pager is in the RESERVED state, the original database file
** is unchanged and we can rollback without having to playback the
** journal into the original database file. Once we transition to
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
do {
rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK);
}while( rc==SQLITE_BUSY &&
pPager->pBusyHandler &&
pPager->pBusyHandler->xFunc &&
pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
);
if( rc!=SQLITE_OK ){
return rc;
}
pPager->state = PAGER_EXCLUSIVE;
while( pList ){
assert( pList->dirty );
sqlite3OsSeek(&pPager->fd, (pList->pgno-1)*(off_t)SQLITE_PAGE_SIZE);
CODEC(pPager, PGHDR_TO_DATA(pList), pList->pgno, 6);
TRACE2("STORE page %d\n", pList->pgno);
rc = sqlite3OsWrite(&pPager->fd, PGHDR_TO_DATA(pList), SQLITE_PAGE_SIZE);
CODEC(pPager, PGHDR_TO_DATA(pList), pList->pgno, 0);
if( rc ) return rc;
pList->dirty = 0;
pList = pList->pDirty;
}
return SQLITE_OK;
}
/*
** Collect every dirty page into a dirty list and
** return a pointer to the head of that list. All pages are
** collected even if they are still in use.
*/
static PgHdr *pager_get_all_dirty_pages(Pager *pPager){
PgHdr *p, *pList;
pList = 0;
for(p=pPager->pAll; p; p=p->pNextAll){
if( p->dirty ){
p->pDirty = pList;
pList = p;
}
}
return pList;
}
/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired.
** This read lock is dropped when the last page is released.
**
** A _get works for any page number greater than 0. If the database
** file is smaller than the requested page, then no actual disk
** read occurs and the memory image of the page is initialized to
** all zeros. The extra data appended to a page is always initialized
** to zeros the first time a page is loaded into memory.
**
** The acquisition might fail for several reasons. In all cases,
** an appropriate error code is returned and *ppPage is set to NULL.
**
** See also sqlite3pager_lookup(). Both this routine and _lookup() attempt
** to find a page in the in-memory cache first. If the page is not already
** in memory, this routine goes to disk to read it in whereas _lookup()
** just returns 0. This routine acquires a read-lock the first time it
** has to go to disk, and could also playback an old journal if necessary.
** Since _lookup() never goes to disk, it never has to deal with locks
** or journal files.
*/
int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
PgHdr *pPg;
int rc;
/* Make sure we have not hit any critical errors.
*/
assert( pPager!=0 );
assert( pgno!=0 );
*ppPage = 0;
if( pPager->errMask & ~(PAGER_ERR_FULL) ){
return pager_errcode(pPager);
}
/* If this is the first page accessed, then get a SHARED lock
** on the database file.
*/
if( pPager->nRef==0 && !pPager->memDb ){
int busy = 1;
do {
rc = sqlite3OsLock(&pPager->fd, SHARED_LOCK);
}while( rc==SQLITE_BUSY &&
pPager->pBusyHandler &&
pPager->pBusyHandler->xFunc &&
pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
);
if( rc!=SQLITE_OK ){
return rc;
}
pPager->state = PAGER_SHARED;
/* If a journal file exists, and there is no RESERVED lock on the
** database file, then it either needs to be played back or deleted.
*/
if( pPager->useJournal &&
sqlite3OsFileExists(pPager->zJournal) &&
!sqlite3OsCheckReservedLock(&pPager->fd)
){
int rc;
/* Get an EXCLUSIVE lock on the database file. */
rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
sqlite3OsUnlock(&pPager->fd, NO_LOCK);
pPager->state = PAGER_UNLOCK;
return rc;
}
pPager->state = PAGER_EXCLUSIVE;
/* Open the journal for reading only. Return SQLITE_BUSY if
** we are unable to open the journal file.
**
** The journal file does not need to be locked itself. The
** journal file is never open unless the main database file holds
** a write lock, so there is never any chance of two or more
** processes opening the journal at the same time.
*/
rc = sqlite3OsOpenReadOnly(pPager->zJournal, &pPager->jfd);
if( rc!=SQLITE_OK ){
sqlite3OsUnlock(&pPager->fd, NO_LOCK);
pPager->state = PAGER_UNLOCK;
return SQLITE_BUSY;
}
pPager->journalOpen = 1;
pPager->journalStarted = 0;
/* Playback and delete the journal. Drop the database write
** lock and reacquire the read lock.
*/
rc = pager_playback(pPager, 0);
if( rc!=SQLITE_OK ){
return rc;
}
}
pPg = 0;
}else{
/* Search for page in cache */
pPg = pager_lookup(pPager, pgno);
if( pPager->memDb && pPager->state==PAGER_UNLOCK ){
pPager->state = PAGER_SHARED;
}
}
if( pPg==0 ){
/* The requested page is not in the page cache. */
int h;
pPager->nMiss++;
if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 || pPager->memDb ){
/* Create a new page */
pPg = sqliteMallocRaw( sizeof(*pPg) + SQLITE_PAGE_SIZE
+ sizeof(u32) + pPager->nExtra
+ pPager->memDb*sizeof(PgHistory) );
if( pPg==0 ){
pager_unwritelock(pPager);
pPager->errMask |= PAGER_ERR_MEM;
return SQLITE_NOMEM;
}
memset(pPg, 0, sizeof(*pPg));
if( pPager->memDb ){
memset(PGHDR_TO_HIST(pPg, pPager), 0, sizeof(PgHistory));
}
pPg->pPager = pPager;
pPg->pNextAll = pPager->pAll;
pPager->pAll = pPg;
pPager->nPage++;
}else{
/* Find a page to recycle. Try to locate a page that does not
** require us to do an fsync() on the journal.
*/
pPg = pPager->pFirstSynced;
/* If we could not find a page that does not require an fsync()
** on the journal file then fsync the journal file. This is a
** very slow operation, so we work hard to avoid it. But sometimes
** it can't be helped.
*/
if( pPg==0 ){
int rc = syncJournal(pPager, 0);
if( rc!=0 ){
sqlite3pager_rollback(pPager);
return SQLITE_IOERR;
}
pPg = pPager->pFirst;
}
assert( pPg->nRef==0 );
/* Write the page to the database file if it is dirty.
*/
if( pPg->dirty ){
assert( pPg->needSync==0 );
pPg->pDirty = 0;
rc = pager_write_pagelist( pPg );
if( rc!=SQLITE_OK ){
sqlite3pager_rollback(pPager);
return SQLITE_IOERR;
}
}
assert( pPg->dirty==0 );
/* If the page we are recycling is marked as alwaysRollback, then
** set the global alwaysRollback flag, thus disabling the
** sqlite_dont_rollback() optimization for the rest of this transaction.
** It is necessary to do this because the page marked alwaysRollback
** might be reloaded at a later time but at that point we won't remember
** that is was marked alwaysRollback. This means that all pages must
** be marked as alwaysRollback from here on out.
*/
if( pPg->alwaysRollback ){
pPager->alwaysRollback = 1;
}
/* Unlink the old page from the free list and the hash table
*/
unlinkPage(pPg);
pPager->nOvfl++;
}
pPg->pgno = pgno;
if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
sqlite3CheckMemory(pPager->aInJournal, pgno/8);
assert( pPager->journalOpen );
pPg->inJournal = (pPager->aInJournal[pgno/8] & (1<<(pgno&7)))!=0;
pPg->needSync = 0;
}else{
pPg->inJournal = 0;
pPg->needSync = 0;
}
if( pPager->aInStmt && (int)pgno<=pPager->stmtSize
&& (pPager->aInStmt[pgno/8] & (1<<(pgno&7)))!=0 ){
page_add_to_stmt_list(pPg);
}else{
page_remove_from_stmt_list(pPg);
}
pPg->dirty = 0;
pPg->nRef = 1;
REFINFO(pPg);
pPager->nRef++;
h = pager_hash(pgno);
pPg->pNextHash = pPager->aHash[h];
pPager->aHash[h] = pPg;
if( pPg->pNextHash ){
assert( pPg->pNextHash->pPrevHash==0 );
pPg->pNextHash->pPrevHash = pPg;
}
if( pPager->nExtra>0 ){
memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
}
if( pPager->dbSize<0 ) sqlite3pager_pagecount(pPager);
if( pPager->errMask!=0 ){
sqlite3pager_unref(PGHDR_TO_DATA(pPg));
rc = pager_errcode(pPager);
return rc;
}
if( pPager->dbSize<(int)pgno ){
memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
}else{
int rc;
assert( pPager->memDb==0 );
sqlite3OsSeek(&pPager->fd, (pgno-1)*(off_t)SQLITE_PAGE_SIZE);
rc = sqlite3OsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
TRACE2("FETCH page %d\n", pPg->pgno);
CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
if( rc!=SQLITE_OK ){
off_t fileSize;
if( sqlite3OsFileSize(&pPager->fd,&fileSize)!=SQLITE_OK
|| fileSize>=pgno*SQLITE_PAGE_SIZE ){
sqlite3pager_unref(PGHDR_TO_DATA(pPg));
return rc;
}else{
memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
}
}
}
}else{
/* The requested page is in the page cache. */
pPager->nHit++;
page_ref(pPg);
}
*ppPage = PGHDR_TO_DATA(pPg);
return SQLITE_OK;
}
/*
** Acquire a page if it is already in the in-memory cache. Do
** not read the page from disk. Return a pointer to the page,
** or 0 if the page is not in cache.
**
** See also sqlite3pager_get(). The difference between this routine
** and sqlite3pager_get() is that _get() will go to the disk and read
** in the page if the page is not already in cache. This routine
** returns NULL if the page is not in cache or if a disk I/O error
** has ever happened.
*/
void *sqlite3pager_lookup(Pager *pPager, Pgno pgno){
PgHdr *pPg;
assert( pPager!=0 );
assert( pgno!=0 );
if( pPager->errMask & ~(PAGER_ERR_FULL) ){
return 0;
}
pPg = pager_lookup(pPager, pgno);
if( pPg==0 ) return 0;
page_ref(pPg);
return PGHDR_TO_DATA(pPg);
}
/*
** Release a page.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list. When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
int sqlite3pager_unref(void *pData){
PgHdr *pPg;
/* Decrement the reference count for this page
*/
pPg = DATA_TO_PGHDR(pData);
assert( pPg->nRef>0 );
pPg->nRef--;
REFINFO(pPg);
/* When the number of references to a page reach 0, call the
** destructor and add the page to the freelist.
*/
if( pPg->nRef==0 ){
Pager *pPager;
pPager = pPg->pPager;
pPg->pNextFree = 0;
pPg->pPrevFree = pPager->pLast;
pPager->pLast = pPg;
if( pPg->pPrevFree ){
pPg->pPrevFree->pNextFree = pPg;
}else{
pPager->pFirst = pPg;
}
if( pPg->needSync==0 && pPager->pFirstSynced==0 ){
pPager->pFirstSynced = pPg;
}
if( pPager->xDestructor ){
pPager->xDestructor(pData, pPager->pageSize);
}
/* When all pages reach the freelist, drop the read lock from
** the database file.
*/
pPager->nRef--;
assert( pPager->nRef>=0 );
if( pPager->nRef==0 && !pPager->memDb ){
pager_reset(pPager);
}
}
return SQLITE_OK;
}
/*
** Create a journal file for pPager. There should already be a RESERVED
** or EXCLUSIVE lock on the database file when this routine is called.
**
** Return SQLITE_OK if everything. Return an error code and release the
** write lock if anything goes wrong.
*/
static int pager_open_journal(Pager *pPager){
int rc;
assert( pPager->state>=PAGER_RESERVED );
assert( pPager->journalOpen==0 );
assert( pPager->useJournal );
sqlite3pager_pagecount(pPager);
pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
if( pPager->aInJournal==0 ){
sqlite3OsUnlock(&pPager->fd, SHARED_LOCK);
pPager->state = PAGER_SHARED;
return SQLITE_NOMEM;
}
rc = sqlite3OsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile);
if( rc!=SQLITE_OK ){
sqliteFree(pPager->aInJournal);
pPager->aInJournal = 0;
sqlite3OsUnlock(&pPager->fd, SHARED_LOCK);
pPager->state = PAGER_SHARED;
return SQLITE_CANTOPEN;
}
sqlite3OsOpenDirectory(pPager->zDirectory, &pPager->jfd);
pPager->journalOpen = 1;
pPager->journalStarted = 0;
pPager->needSync = 0;
pPager->alwaysRollback = 0;
pPager->nRec = 0;
if( pPager->errMask!=0 ){
rc = pager_errcode(pPager);
return rc;
}
pPager->origDbSize = pPager->dbSize;
/* Create the header for the journal:
** - 8 bytes: Magic identifying journal format.
** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
** - 4 bytes: Magic used for page checksums.
** - 4 bytes: Initial database page count.
** - 4 bytes: Number of bytes reserved for master journal ptr (nMaster)
** - nMaster bytes: Space for a master journal pointer.
*/
rc = sqlite3OsWrite(&pPager->jfd, aJournalMagic, sizeof(aJournalMagic));
if( rc==SQLITE_OK ){
rc = write32bits(&pPager->jfd, pPager->noSync ? 0xffffffff : 0);
}
if( rc==SQLITE_OK ){
sqlite3Randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
rc = write32bits(&pPager->jfd, pPager->cksumInit);
}
if( rc==SQLITE_OK ){
rc = write32bits(&pPager->jfd, pPager->dbSize);
}
if( rc==SQLITE_OK ){
rc = write32bits(&pPager->jfd, pPager->nMaster);
}
if( rc==SQLITE_OK ){
sqlite3OsSeek(&pPager->jfd, 24 + pPager->nMaster - 1);
rc = sqlite3OsWrite(&pPager->jfd, "\000", 1);
}
if( pPager->stmtAutoopen && rc==SQLITE_OK ){
rc = sqlite3pager_stmt_begin(pPager);
}
if( rc!=SQLITE_OK ){
rc = pager_unwritelock(pPager);
if( rc==SQLITE_OK ){
rc = SQLITE_FULL;
}
}
return rc;
}
/*
** Acquire a write-lock on the database. The lock is removed when
** the any of the following happen:
**
** * sqlite3pager_commit() is called.
** * sqlite3pager_rollback() is called.
** * sqlite3pager_close() is called.
** * sqlite3pager_unref() is called to on every outstanding page.
**
** The first parameter to this routine is a pointer to any open page of the
** database file. Nothing changes about the page - it is used merely to
** acquire a pointer to the Pager structure and as proof that there is
** already a read-lock on the database.
**
** The second parameter indicates how much space in bytes to reserve for a
** master journal file-name at the start of the journal when it is created.
**
** A journal file is opened if this is not a temporary file. For temporary
** files, the opening of the journal file is deferred until there is an
** actual need to write to the journal.
**
** If the database is already reserved for writing, this routine is a no-op.
*/
int sqlite3pager_begin(void *pData, int nMaster){
PgHdr *pPg = DATA_TO_PGHDR(pData);
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
assert( pPg->nRef>0 );
assert( nMaster>=0 );
assert( pPager->state!=PAGER_UNLOCK );
if( pPager->state==PAGER_SHARED ){
assert( pPager->aInJournal==0 );
if( pPager->memDb ){
pPager->state = PAGER_EXCLUSIVE;
pPager->origDbSize = pPager->dbSize;
}else{
int busy = 1;
do {
rc = sqlite3OsLock(&pPager->fd, RESERVED_LOCK);
}while( rc==SQLITE_BUSY &&
pPager->pBusyHandler &&
pPager->pBusyHandler->xFunc &&
pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
);
if( rc!=SQLITE_OK ){
return rc;
}
pPager->nMaster = nMaster;
pPager->state = PAGER_RESERVED;
pPager->dirtyCache = 0;
TRACE3("TRANSACTION %d nMaster=%d\n", pPager->fd.h, nMaster);
if( pPager->useJournal && !pPager->tempFile ){
rc = pager_open_journal(pPager);
}
}
}
return rc;
}
/*
** Mark a data page as writeable. The page is written into the journal
** if it is not there already. This routine must be called before making
** changes to a page.
**
** The first time this routine is called, the pager creates a new
** journal and acquires a RESERVED lock on the database. If the RESERVED
** lock could not be acquired, this routine returns SQLITE_BUSY. The
** calling routine must check for that return value and be careful not to
** change any page data until this routine returns SQLITE_OK.
**
** If the journal file could not be written because the disk is full,
** then this routine returns SQLITE_FULL and does an immediate rollback.
** All subsequent write attempts also return SQLITE_FULL until there
** is a call to sqlite3pager_commit() or sqlite3pager_rollback() to
** reset.
*/
int sqlite3pager_write(void *pData){
PgHdr *pPg = DATA_TO_PGHDR(pData);
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
/* Check for errors
*/
if( pPager->errMask ){
return pager_errcode(pPager);
}
if( pPager->readOnly ){
return SQLITE_PERM;
}
/* Mark the page as dirty. If the page has already been written
** to the journal then we can return right away.
*/
pPg->dirty = 1;
if( pPg->inJournal && (pPg->inStmt || pPager->stmtInUse==0) ){
pPager->dirtyCache = 1;
return SQLITE_OK;
}
/* If we get this far, it means that the page needs to be
** written to the transaction journal or the ckeckpoint journal
** or both.
**
** First check to see that the transaction journal exists and
** create it if it does not.
*/
assert( pPager->state!=PAGER_UNLOCK );
rc = sqlite3pager_begin(pData, 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 || pPager->memDb) ){
if( (int)pPg->pgno <= pPager->origDbSize ){
int szPg;
u32 saved;
if( pPager->memDb ){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
TRACE2("JOURNAL page %d\n", pPg->pgno);
assert( pHist->pOrig==0 );
pHist->pOrig = sqliteMallocRaw( pPager->pageSize );
if( pHist->pOrig ){
memcpy(pHist->pOrig, PGHDR_TO_DATA(pPg), pPager->pageSize);
}
pPg->inJournal = 1;
}else{
u32 cksum = pager_cksum(pPager, pPg->pgno, pData);
saved = *(u32*)PGHDR_TO_EXTRA(pPg);
store32bits(cksum, pPg, SQLITE_PAGE_SIZE);
szPg = SQLITE_PAGE_SIZE+8;
store32bits(pPg->pgno, pPg, -4);
CODEC(pPager, pData, pPg->pgno, 7);
rc = sqlite3OsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
TRACE3("JOURNAL page %d needSync=%d\n", pPg->pgno, pPg->needSync);
CODEC(pPager, pData, pPg->pgno, 0);
*(u32*)PGHDR_TO_EXTRA(pPg) = saved;
if( rc!=SQLITE_OK ){
sqlite3pager_rollback(pPager);
pPager->errMask |= PAGER_ERR_FULL;
return rc;
}
pPager->nRec++;
assert( pPager->aInJournal!=0 );
pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
pPg->needSync = !pPager->noSync;
pPg->inJournal = 1;
if( pPager->stmtInUse ){
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
page_add_to_stmt_list(pPg);
}
}
}else{
pPg->needSync = !pPager->journalStarted && !pPager->noSync;
TRACE3("APPEND page %d needSync=%d\n", pPg->pgno, pPg->needSync);
}
if( pPg->needSync ){
pPager->needSync = 1;
}
}
/* If the statement journal is open and the page is not in it,
** then write the current page to the statement journal. Note that
** the statement journal format differs from the standard journal format
** in that it omits the checksums and the header.
*/
if( pPager->stmtInUse && !pPg->inStmt && (int)pPg->pgno<=pPager->stmtSize ){
assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
if( pPager->memDb ){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
assert( pHist->pStmt==0 );
pHist->pStmt = sqliteMallocRaw( pPager->pageSize );
if( pHist->pStmt ){
memcpy(pHist->pStmt, PGHDR_TO_DATA(pPg), pPager->pageSize);
}
TRACE2("STMT-JOURNAL page %d\n", pPg->pgno);
}else{
store32bits(pPg->pgno, pPg, -4);
CODEC(pPager, pData, pPg->pgno, 7);
rc = sqlite3OsWrite(&pPager->stfd, ((char*)pData)-4, SQLITE_PAGE_SIZE+4);
TRACE2("STMT-JOURNAL page %d\n", pPg->pgno);
CODEC(pPager, pData, pPg->pgno, 0);
if( rc!=SQLITE_OK ){
sqlite3pager_rollback(pPager);
pPager->errMask |= PAGER_ERR_FULL;
return rc;
}
pPager->stmtNRec++;
assert( pPager->aInStmt!=0 );
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
}
page_add_to_stmt_list(pPg);
}
/* Update the database size and return.
*/
if( pPager->dbSize<(int)pPg->pgno ){
pPager->dbSize = pPg->pgno;
if( !pPager->memDb && pPager->dbSize==PENDING_BYTE/pPager->pageSize ){
pPager->dbSize++;
}
}
return rc;
}
/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3pager_write(). In other words, return TRUE if it is ok
** to change the content of the page.
*/
int sqlite3pager_iswriteable(void *pData){
PgHdr *pPg = DATA_TO_PGHDR(pData);
return pPg->dirty;
}
/*
** Replace the content of a single page with the information in the third
** argument.
*/
int sqlite3pager_overwrite(Pager *pPager, Pgno pgno, void *pData){
void *pPage;
int rc;
rc = sqlite3pager_get(pPager, pgno, &pPage);
if( rc==SQLITE_OK ){
rc = sqlite3pager_write(pPage);
if( rc==SQLITE_OK ){
memcpy(pPage, pData, SQLITE_PAGE_SIZE);
}
sqlite3pager_unref(pPage);
}
return rc;
}
/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page "pgno" back to the disk, even though
** that page might be marked as dirty.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused. The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization, together with the
** sqlite3pager_dont_rollback() below, more than double the speed
** of large INSERT operations and quadruple the speed of large DELETEs.
**
** When this routine is called, set the alwaysRollback flag to true.
** Subsequent calls to sqlite3pager_dont_rollback() for the same page
** will thereafter be ignored. This is necessary to avoid a problem
** where a page with data is added to the freelist during one part of
** a transaction then removed from the freelist during a later part
** of the same transaction and reused for some other purpose. When it
** is first added to the freelist, this routine is called. When reused,
** the dont_rollback() routine is called. But because the page contains
** critical data, we still need to be sure it gets rolled back in spite
** of the dont_rollback() call.
*/
void sqlite3pager_dont_write(Pager *pPager, Pgno pgno){
PgHdr *pPg;
pPg = pager_lookup(pPager, pgno);
pPg->alwaysRollback = 1;
if( pPg && pPg->dirty ){
if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
/* If this pages is the last page in the file and the file has grown
** during the current transaction, then do NOT mark the page as clean.
** When the database file grows, we must make sure that the last page
** gets written at least once so that the disk file will be the correct
** size. If you do not write this page and the size of the file
** on the disk ends up being too small, that can lead to database
** corruption during the next transaction.
*/
}else{
TRACE3("DONT_WRITE page %d of %d\n", pgno, pPager->fd.h);
pPg->dirty = 0;
}
}
}
/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page. This
** means that the pager does not have to record the given page in the
** rollback journal.
*/
void sqlite3pager_dont_rollback(void *pData){
PgHdr *pPg = DATA_TO_PGHDR(pData);
Pager *pPager = pPg->pPager;
if( pPager->state!=PAGER_EXCLUSIVE || pPager->journalOpen==0 ) return;
if( pPg->alwaysRollback || pPager->alwaysRollback || pPager->memDb ) return;
if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){
assert( pPager->aInJournal!=0 );
pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
pPg->inJournal = 1;
if( pPager->stmtInUse ){
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
page_add_to_stmt_list(pPg);
}
TRACE3("DONT_ROLLBACK page %d of %d\n", pPg->pgno, pPager->fd.h);
}
if( pPager->stmtInUse && !pPg->inStmt && (int)pPg->pgno<=pPager->stmtSize ){
assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
assert( pPager->aInStmt!=0 );
pPager->aInStmt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
page_add_to_stmt_list(pPg);
}
}
/*
** Clear a PgHistory block
*/
static void clearHistory(PgHistory *pHist){
sqliteFree(pHist->pOrig);
sqliteFree(pHist->pStmt);
pHist->pOrig = 0;
pHist->pStmt = 0;
}
/*
** Commit all changes to the database and release the write lock.
**
** If the commit fails for any reason, a rollback attempt is made
** and an error code is returned. If the commit worked, SQLITE_OK
** is returned.
*/
int sqlite3pager_commit(Pager *pPager){
int rc;
PgHdr *pPg;
if( pPager->errMask==PAGER_ERR_FULL ){
rc = sqlite3pager_rollback(pPager);
if( rc==SQLITE_OK ){
rc = SQLITE_FULL;
}
return rc;
}
if( pPager->errMask!=0 ){
rc = pager_errcode(pPager);
return rc;
}
if( pPager->state<PAGER_RESERVED ){
return SQLITE_ERROR;
}
TRACE2("COMMIT %d\n", pPager->fd.h);
if( pPager->memDb ){
pPg = pager_get_all_dirty_pages(pPager);
while( pPg ){
clearHistory(PGHDR_TO_HIST(pPg, pPager));
pPg->dirty = 0;
pPg->inJournal = 0;
pPg->inStmt = 0;
pPg->pPrevStmt = pPg->pNextStmt = 0;
pPg = pPg->pDirty;
}
pPager->pStmt = 0;
pPager->state = PAGER_SHARED;
return SQLITE_OK;
}
if( pPager->dirtyCache==0 ){
/* Exit early (without doing the time-consuming sqlite3OsSync() calls)
** if there have been no changes to the database file. */
assert( pPager->needSync==0 );
rc = pager_unwritelock(pPager);
pPager->dbSize = -1;
return rc;
}
assert( pPager->journalOpen );
#if 0
rc = syncJournal(pPager, 0);
if( rc!=SQLITE_OK ){
goto commit_abort;
}
pPg = pager_get_all_dirty_pages(pPager);
if( pPg ){
rc = pager_write_pagelist(pPg);
if( rc || (!pPager->noSync && sqlite3OsSync(&pPager->fd)!=SQLITE_OK) ){
goto commit_abort;
}
}
#endif
rc = sqlite3pager_sync(pPager, 0);
if( rc!=SQLITE_OK ){
goto commit_abort;
}
rc = pager_unwritelock(pPager);
pPager->dbSize = -1;
return rc;
/* Jump here if anything goes wrong during the commit process.
*/
commit_abort:
rc = sqlite3pager_rollback(pPager);
if( rc==SQLITE_OK ){
rc = SQLITE_FULL;
}
return rc;
}
/*
** Rollback all changes. The database falls back to PAGER_SHARED mode.
** All in-memory cache pages revert to their original data contents.
** The journal is deleted.
**
** This routine cannot fail unless some other process is not following
** the correct locking protocol (SQLITE_PROTOCOL) or unless some other
** process is writing trash into the journal file (SQLITE_CORRUPT) or
** unless a prior malloc() failed (SQLITE_NOMEM). Appropriate error
** codes are returned for all these occasions. Otherwise,
** SQLITE_OK is returned.
*/
int sqlite3pager_rollback(Pager *pPager){
int rc;
TRACE2("ROLLBACK %d\n", pPager->fd.h);
if( pPager->memDb ){
PgHdr *p;
for(p=pPager->pAll; p; p=p->pNextAll){
PgHistory *pHist;
if( !p->alwaysRollback && !p->dirty ) continue;
pHist = PGHDR_TO_HIST(p, pPager);
if( pHist->pOrig ){
memcpy(PGHDR_TO_DATA(p), pHist->pOrig, pPager->pageSize);
TRACE2("ROLLBACK-PAGE %d\n", p->pgno);
}else{
TRACE2("PAGE %d is clean\n", p->pgno);
}
clearHistory(pHist);
p->dirty = 0;
p->inJournal = 0;
p->inStmt = 0;
p->pPrevStmt = p->pNextStmt = 0;
if( pPager->xReiniter ){
pPager->xReiniter(PGHDR_TO_DATA(p), pPager->pageSize);
}
}
pPager->pStmt = 0;
pPager->dbSize = pPager->origDbSize;
memoryTruncate(pPager);
pPager->stmtInUse = 0;
pPager->state = PAGER_SHARED;
return SQLITE_OK;
}
if( !pPager->dirtyCache || !pPager->journalOpen ){
rc = pager_unwritelock(pPager);
pPager->dbSize = -1;
return rc;
}
if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){
if( pPager->state>=PAGER_EXCLUSIVE ){
pager_playback(pPager, 1);
}
return pager_errcode(pPager);
}
if( pPager->state==PAGER_RESERVED ){
int rc2;
rc = pager_reload_cache(pPager);
rc2 = pager_unwritelock(pPager);
if( rc==SQLITE_OK ){
rc = rc2;
}
}else{
rc = pager_playback(pPager, 1);
}
if( rc!=SQLITE_OK ){
rc = SQLITE_CORRUPT;
pPager->errMask |= PAGER_ERR_CORRUPT;
}
pPager->dbSize = -1;
return rc;
}
/*
** Return TRUE if the database file is opened read-only. Return FALSE
** if the database is (in theory) writable.
*/
int sqlite3pager_isreadonly(Pager *pPager){
return pPager->readOnly;
}
/*
** This routine is used for testing and analysis only.
*/
int *sqlite3pager_stats(Pager *pPager){
static int a[9];
a[0] = pPager->nRef;
a[1] = pPager->nPage;
a[2] = pPager->mxPage;
a[3] = pPager->dbSize;
a[4] = pPager->state;
a[5] = pPager->errMask;
a[6] = pPager->nHit;
a[7] = pPager->nMiss;
a[8] = pPager->nOvfl;
return a;
}
/*
** Set the statement rollback point.
**
** This routine should be called with the transaction journal already
** open. A new statement journal is created that can be used to rollback
** changes of a single SQL command within a larger transaction.
*/
int sqlite3pager_stmt_begin(Pager *pPager){
int rc;
char zTemp[SQLITE_TEMPNAME_SIZE];
assert( !pPager->stmtInUse );
TRACE2("STMT-BEGIN %d\n", pPager->fd.h);
if( pPager->memDb ){
pPager->stmtInUse = 1;
pPager->stmtSize = pPager->dbSize;
return SQLITE_OK;
}
if( !pPager->journalOpen ){
pPager->stmtAutoopen = 1;
return SQLITE_OK;
}
assert( pPager->journalOpen );
pPager->aInStmt = sqliteMalloc( pPager->dbSize/8 + 1 );
if( pPager->aInStmt==0 ){
sqlite3OsLock(&pPager->fd, SHARED_LOCK);
return SQLITE_NOMEM;
}
#ifndef NDEBUG
rc = sqlite3OsFileSize(&pPager->jfd, &pPager->stmtJSize);
if( rc ) goto stmt_begin_failed;
assert( pPager->stmtJSize ==
pPager->nRec*JOURNAL_PG_SZ(pPager) + JOURNAL_HDR_SZ(pPager) );
#endif
pPager->stmtJSize =
pPager->nRec*JOURNAL_PG_SZ(pPager) + JOURNAL_HDR_SZ(pPager);
pPager->stmtSize = pPager->dbSize;
if( !pPager->stmtOpen ){
rc = sqlite3pager_opentemp(zTemp, &pPager->stfd);
if( rc ) goto stmt_begin_failed;
pPager->stmtOpen = 1;
pPager->stmtNRec = 0;
}
pPager->stmtInUse = 1;
return SQLITE_OK;
stmt_begin_failed:
if( pPager->aInStmt ){
sqliteFree(pPager->aInStmt);
pPager->aInStmt = 0;
}
return rc;
}
/*
** Commit a statement.
*/
int sqlite3pager_stmt_commit(Pager *pPager){
if( pPager->stmtInUse ){
PgHdr *pPg, *pNext;
TRACE2("STMT-COMMIT %d\n", pPager->fd.h);
if( !pPager->memDb ){
sqlite3OsSeek(&pPager->stfd, 0);
/* sqlite3OsTruncate(&pPager->stfd, 0); */
sqliteFree( pPager->aInStmt );
pPager->aInStmt = 0;
}
for(pPg=pPager->pStmt; pPg; pPg=pNext){
pNext = pPg->pNextStmt;
assert( pPg->inStmt );
pPg->inStmt = 0;
pPg->pPrevStmt = pPg->pNextStmt = 0;
if( pPager->memDb ){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
sqliteFree(pHist->pStmt);
pHist->pStmt = 0;
}
}
pPager->stmtNRec = 0;
pPager->stmtInUse = 0;
pPager->pStmt = 0;
}
pPager->stmtAutoopen = 0;
return SQLITE_OK;
}
/*
** Rollback a statement.
*/
int sqlite3pager_stmt_rollback(Pager *pPager){
int rc;
if( pPager->stmtInUse ){
TRACE2("STMT-ROLLBACK %d\n", pPager->fd.h);
if( pPager->memDb ){
PgHdr *pPg;
for(pPg=pPager->pStmt; pPg; pPg=pPg->pNextStmt){
PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
if( pHist->pStmt ){
memcpy(PGHDR_TO_DATA(pPg), pHist->pStmt, pPager->pageSize);
sqliteFree(pHist->pStmt);
pHist->pStmt = 0;
}
}
pPager->dbSize = pPager->stmtSize;
memoryTruncate(pPager);
rc = SQLITE_OK;
}else{
rc = pager_stmt_playback(pPager);
}
sqlite3pager_stmt_commit(pPager);
}else{
rc = SQLITE_OK;
}
pPager->stmtAutoopen = 0;
return rc;
}
/*
** Return the full pathname of the database file.
*/
const char *sqlite3pager_filename(Pager *pPager){
return pPager->zFilename;
}
/*
** Return the directory of the database file.
*/
const char *sqlite3pager_dirname(Pager *pPager){
return pPager->zDirectory;
}
/*
** Return the full pathname of the journal file.
*/
const char *sqlite3pager_journalname(Pager *pPager){
return pPager->zJournal;
}
/*
** Set the codec for this pager
*/
void sqlite3pager_set_codec(
Pager *pPager,
void (*xCodec)(void*,void*,Pgno,int),
void *pCodecArg
){
pPager->xCodec = xCodec;
pPager->pCodecArg = pCodecArg;
}
/*
** This routine is called to increment the database file change-counter,
** stored at byte 24 of the pager file.
*/
static int pager_incr_changecounter(Pager *pPager){
void *pPage;
PgHdr *pPgHdr;
u32 change_counter;
int rc;
/* Open page 1 of the file for writing. */
rc = sqlite3pager_get(pPager, 1, &pPage);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3pager_write(pPage);
if( rc!=SQLITE_OK ) return rc;
/* Read the current value at byte 24. */
pPgHdr = DATA_TO_PGHDR(pPage);
change_counter = retrieve32bits(pPgHdr, 24);
/* Increment the value just read and write it back to byte 24. */
change_counter++;
store32bits(change_counter, pPgHdr, 24);
/* Release the page reference. */
sqlite3pager_unref(pPage);
return SQLITE_OK;
}
/*
** Sync the database file for the pager pPager. zMaster points to the name
** of a master journal file that should be written into the individual
** journal file. zMaster may be NULL, which is interpreted as no master
** journal (a single database transaction).
**
** This routine ensures that the journal is synced, all dirty pages written
** to the database file and the database file synced. The only thing that
** remains to commit the transaction is to delete the journal file (or
** master journal file if specified).
**
** Note that if zMaster==NULL, this does not overwrite a previous value
** passed to an sqlite3pager_sync() call.
*/
int sqlite3pager_sync(Pager *pPager, const char *zMaster){
int rc = SQLITE_OK;
/* If this is an in-memory db, or no pages have been written to, or this
** function has already been called, it is a no-op.
*/
if( pPager->state!=PAGER_SYNCED && !pPager->memDb && pPager->dirtyCache ){
PgHdr *pPg;
assert( pPager->journalOpen );
rc = pager_incr_changecounter(pPager);
if( rc!=SQLITE_OK ) goto sync_exit;
/* Sync the journal file */
rc = syncJournal(pPager, zMaster);
if( rc!=SQLITE_OK ) goto sync_exit;
/* Write all dirty pages to the database file */
pPg = pager_get_all_dirty_pages(pPager);
rc = pager_write_pagelist(pPg);
if( rc!=SQLITE_OK ) goto sync_exit;
/* Sync the database file. */
if( !pPager->noSync ){
rc = sqlite3OsSync(&pPager->fd);
}
pPager->state = PAGER_SYNCED;
}
sync_exit:
return rc;
}
#ifdef SQLITE_DEBUG
/*
** Return the current state of the file lock for the given pager.
** The return value is one of NO_LOCK, SHARED_LOCK, RESERVED_LOCK,
** PENDING_LOCK, or EXCLUSIVE_LOCK.
*/
int sqlite3pager_lockstate(Pager *pPager){
return pPager->fd.locktype;
}
#endif
#ifdef SQLITE_TEST
/*
** Print a listing of all referenced pages and their ref count.
*/
void sqlite3pager_refdump(Pager *pPager){
PgHdr *pPg;
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
if( pPg->nRef<=0 ) continue;
printf("PAGE %3d addr=0x%08x nRef=%d\n",
pPg->pgno, (int)PGHDR_TO_DATA(pPg), pPg->nRef);
}
}
#endif