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Add code to reduce rollback journal i/o based on IOCAP flags. As yet untested. (CVS 4278)

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FossilOrigin-Name: 595568492e63822caed5b6970542dcee4615dc4d
This commit is contained in:
danielk1977
2007-08-23 14:48:23 +00:00
parent 863c0f9b87
commit 4cd2cd5c69
3 changed files with 67 additions and 31 deletions
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84
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 1.370 2007/08/23 11:47:59 danielk1977 Exp $
** @(#) $Id: pager.c,v 1.371 2007/08/23 14:48:24 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
@@ -822,17 +822,37 @@ static int writeJournalHdr(Pager *pPager){
seekJournalHdr(pPager);
pPager->journalHdr = pPager->journalOff;
/* 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);
/*
** Write the nRec Field - the number of page records that follow this
** journal header. Normally, zero is written to this value at this time.
** After the records are added to the journal (and the journal synced,
** if in full-sync mode), the zero is overwritten with the true number
** of records (see syncJournal()).
**
** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
** reading the journal this value tells SQLite to assume that the
** rest of the journal file contains valid page records. This assumption
** is dangerous, as if a failure occured whilst writing to the journal
** file it may contain some garbage data. There are two scenarios
** where this risk can be ignored:
**
** * When the pager is in no-sync mode. Corruption can follow a
** power failure in this case anyway.
**
** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
** that garbage data is never appended to the journal file.
*/
assert(pPager->fd->pMethods||pPager->noSync);
if( (pPager->noSync)
|| (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
){
put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
}else{
put32bits(&zHeader[sizeof(aJournalMagic)], 0);
}
/* The random check-hash initialiser */
sqlite3Randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
@@ -2484,7 +2504,12 @@ int sqlite3PagerRef(DbPage *pPg){
** 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.
** after a power failure, so no sync occurs.
**
** If the IOCAP_SEQUENTIAL flag is set for the persistent media on which
** the database is stored, then OsSync() is never called on the journal
** file. In this case all that is required is to update the nRec field in
** the journal header.
**
** This routine clears the needSync field of every page current held in
** memory.
@@ -2493,12 +2518,15 @@ 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 ){
int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
assert( pPager->journalOpen );
/* assert( !pPager->noSync ); // noSync might be set if synchronous
** was turned off after the transaction was started. Ticket #615 */
#ifndef NDEBUG
@@ -2512,15 +2540,20 @@ static int syncJournal(Pager *pPager){
assert( pPager->journalOff==jSz );
}
#endif
{
i64 jrnlOff;
if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
/* 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.
** it as a candidate for rollback.
**
** This is not required if the persistent media supports the
** SAFE_APPEND property. Because in this case it is not possible
** for garbage data to be appended to the file, the nRec field
** is populated with 0xFFFFFFFF when the journal header is written
** and never needs to be updated.
*/
if( pPager->fullSync ){
i64 jrnlOff;
if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags);
@@ -2532,12 +2565,14 @@ static int syncJournal(Pager *pPager){
rc = write32bits(pPager->jfd, jrnlOff, pPager->nRec);
if( rc ) return rc;
}
PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags|
(pPager->sync_flags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
);
if( rc!=0 ) return rc;
if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags|
(pPager->sync_flags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
);
if( rc!=0 ) return rc;
}
pPager->journalStarted = 1;
}
pPager->needSync = 0;
@@ -2774,11 +2809,12 @@ static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
** it can't be helped.
*/
if( pPg==0 && pPager->pFirst && syncOk && !MEMDB){
int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
int rc = syncJournal(pPager);
if( rc!=0 ){
return rc;
}
if( pPager->fullSync ){
if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
/* 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