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Add code for the atomic-write optimisation. Disabled by default. (CVS 4268)

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FossilOrigin-Name: 581fadfe31757e3fb97b12f93c1e3c085e4b6009
This commit is contained in:
danielk1977
2007-08-22 11:22:03 +00:00
parent 1f12f9aa30
commit c7b6017c8a
7 changed files with 356 additions and 30 deletions
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112
src/pager.c
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@@ -18,7 +18,7 @@
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.365 2007/08/22 00:39:20 drh Exp $
** @(#) $Id: pager.c,v 1.366 2007/08/22 11:22:04 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
@@ -603,6 +603,42 @@ static int osUnlock(sqlite3_file *pFd, int eLock){
return sqlite3OsUnlock(pFd, eLock);
}
/*
** This function determines whether or not the atomic-write optimization
** can be used with this pager. The optimization can be used if:
**
** (a) the value returned by OsDeviceCharacteristics() indicates that
** a database page may be written atomically, and
** (b) the value returned by OsSectorSize() is less than or equal
** to the page size.
**
** If the optimization cannot be used, 0 is returned. If it can be used,
** then the value returned is the size of the journal file when it
** contains rollback data for exactly one page.
*/
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
static int jrnlBufferSize(Pager *pPager){
int dc; /* Device characteristics */
int nSector; /* Sector size */
int nPage; /* Page size */
sqlite3_file *fd = pPager->fd;
if( fd->pMethods ){
dc = sqlite3OsDeviceCharacteristics(fd);
nSector = sqlite3OsSectorSize(fd);
nPage = pPager->pageSize;
}
assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
if( !fd->pMethods || (dc&(SQLITE_IOCAP_ATOMIC|(nPage<<8))&&nSector<=nPage) ){
return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
}
return 0;
}
#endif
/*
** This function should be called when an error occurs within the pager
** code. The first argument is a pointer to the pager structure, the
@@ -1820,6 +1856,7 @@ int sqlite3PagerOpen(
int readOnly = 0;
int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
int journalFileSize = sqlite3JournalSize(pVfs);
/* The default return is a NULL pointer */
*ppPager = 0;
@@ -1827,7 +1864,8 @@ int sqlite3PagerOpen(
/* Allocate memory for the pager structure */
pPager = sqlite3MallocZero(
sizeof(*pPager) + /* Pager structure */
pVfs->szOsFile * 3 + /* The db, journal and stmt journal files */
journalFileSize + /* The journal file structure */
pVfs->szOsFile * 2 + /* The db and stmt journal files */
pVfs->mxPathname * 3 + 30 /* zFilename, zDirectory, zJournal */
);
if( !pPager ){
@@ -1835,9 +1873,9 @@ int sqlite3PagerOpen(
}
pPtr = (u8 *)&pPager[1];
pPager->fd = (sqlite3_file*)&pPtr[pVfs->szOsFile*0];
pPager->jfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*1];
pPager->stfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*2];
pPager->zFilename = (char*)&pPtr[pVfs->szOsFile*3];
pPager->stfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*1];
pPager->jfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*2];
pPager->zFilename = (char*)&pPtr[pVfs->szOsFile*2+journalFileSize];
pPager->zDirectory = &pPager->zFilename[pVfs->mxPathname];
pPager->zJournal = &pPager->zDirectory[pVfs->mxPathname];
pPager->pVfs = pVfs;
@@ -1871,7 +1909,6 @@ int sqlite3PagerOpen(
** In this case we accept the default page size and delay actually
** opening the file until the first call to OsWrite().
*/
/* rc = sqlite3PagerOpentemp(pVfs, pPager->fd, pPager->zFilename); */
tempFile = 1;
pPager->state = PAGER_EXCLUSIVE;
}
@@ -2998,7 +3035,7 @@ static int pagerSharedLock(Pager *pPager){
int fout = 0;
int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
assert( !pPager->tempFile );
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, &fout);
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags,&fout);
assert( rc!=SQLITE_OK || pPager->jfd->pMethods );
if( fout&SQLITE_OPEN_READONLY ){
rc = SQLITE_BUSY;
@@ -3460,7 +3497,13 @@ static int pager_open_journal(Pager *pPager){
}else{
flags |= (SQLITE_OPEN_MAIN_JOURNAL);
}
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
rc = sqlite3JournalOpen(
pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
);
#else
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
#endif
assert( rc!=SQLITE_OK || pPager->jfd->pMethods );
pPager->journalOff = 0;
pPager->setMaster = 0;
@@ -4010,27 +4053,36 @@ void sqlite3PagerDontRollback(DbPage *pPg){
** 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){
static int pager_incr_changecounter(Pager *pPager, int isDirect){
PgHdr *pPgHdr;
u32 change_counter;
int rc;
int rc = SQLITE_OK;
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;
if( !isDirect ){
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);
if( isDirect && pPager->fd->pMethods ){
const void *zBuf = PGHDR_TO_DATA(pPgHdr);
rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
}
/* Release the page reference. */
sqlite3PagerUnref(pPgHdr);
pPager->changeCountDone = 1;
}
return SQLITE_OK;
return rc;
}
/*
@@ -4064,6 +4116,36 @@ int sqlite3PagerCommitPhaseOne(Pager *pPager, const char *zMaster, Pgno nTrunc){
PgHdr *pPg;
assert( pPager->journalOpen );
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
/* The atomic-write optimization can be used if all of the
** following are true:
**
** + The file-system supports the atomic-write property for
** blocks of size page-size, and
** + This commit is not part of a multi-file transaction, and
** + Exactly one page has been modified and store in the journal file.
**
** If the optimization can be used, then the journal file will never
** be created for this transaction.
*/
if( !zMaster && pPager->journalOff==jrnlBufferSize(pPager) && nTrunc==0
&& (0==pPager->pDirty || 0==pPager->pDirty->pDirty)
){
/* Update the nRec field in the journal file. */
int offset = pPager->journalHdr + sizeof(aJournalMagic);
assert(pPager->nRec==1);
rc = write32bits(pPager->jfd, offset, pPager->nRec);
/* Update the db file change counter. The following call will modify
** the in-memory representation of page 1 to include the updated
** change counter and then write page 1 directly to the database
** file. Because of the atomic-write property of the host file-system,
** this is safe.
*/
rc = pager_incr_changecounter(pPager, 1);
}else
#endif
/* 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
@@ -4071,7 +4153,7 @@ int sqlite3PagerCommitPhaseOne(Pager *pPager, const char *zMaster, Pgno nTrunc){
** transaction the m-j name will have already been written.
*/
if( !pPager->setMaster ){
rc = pager_incr_changecounter(pPager);
rc = pager_incr_changecounter(pPager, 0);
if( rc!=SQLITE_OK ) goto sync_exit;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( nTrunc!=0 ){
@@ -4095,8 +4177,8 @@ int sqlite3PagerCommitPhaseOne(Pager *pPager, const char *zMaster, Pgno nTrunc){
rc = writeMasterJournal(pPager, zMaster);
if( rc!=SQLITE_OK ) goto sync_exit;
rc = syncJournal(pPager);
if( rc!=SQLITE_OK ) goto sync_exit;
}
if( rc!=SQLITE_OK ) goto sync_exit;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( nTrunc!=0 ){