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More changes for ticket #1171 after additional analysis. (CVS 2403)

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FossilOrigin-Name: 0471d6b86fd67c22da832beb280b31305c5aa812
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drh
2005-03-20 22:47:56 +00:00
parent 41712ef171
commit 9636284e32
3 changed files with 31 additions and 16 deletions
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33
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 1.195 2005/03/20 19:10:12 drh Exp $
** @(#) $Id: pager.c,v 1.196 2005/03/20 22:47:57 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
@@ -935,6 +935,12 @@ static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int useCksum){
u32 cksum; /* Checksum used for sanity checking */
u8 aData[SQLITE_MAX_PAGE_SIZE]; /* Temp storage for a page */
/* useCksum should be true for the main journal and false for
** statement journals. Verify that this is always the case
*/
assert( jfd == (useCksum ? &pPager->jfd : &pPager->stfd) );
rc = read32bits(jfd, &pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(jfd, &aData, pPager->pageSize);
@@ -969,14 +975,27 @@ static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int useCksum){
**
** If in EXCLUSIVE state, then we update the pager cache if it exists
** and the main file. The page is then marked not dirty.
**
** Ticket #1171: The statement journal might contain page content that is
** different from the page content at the start of the transaction.
** This occurs when a page is changed prior to the start of a statement
** then changed again within the statement. When rolling back such a
** statement we must not write to the original database unless we know
** for certain that original page contents are in the main rollback
** journal. Otherwise, if a full ROLLBACK occurs after the statement
** rollback the full ROLLBACK will not restore the page to its original
** content. Two conditions must be met before writing to the database
** files. (1) the database must be locked. (2) we know that the original
** page content is in the main journal either because the page is not in
** cache or else it is marked as needSync==0.
*/
pPg = pager_lookup(pPager, pgno);
assert( pPager->state>=PAGER_EXCLUSIVE || pPg );
assert( pPager->state>=PAGER_EXCLUSIVE || pPg!=0 );
TRACE3("PLAYBACK %d page %d\n", PAGERID(pPager), pgno);
assert( jfd == (useCksum ? &pPager->jfd : &pPager->stfd) );
if( pPager->state>=PAGER_EXCLUSIVE && (useCksum || !pPg || !pPg->needSync) ){
if( pPager->state>=PAGER_EXCLUSIVE && (pPg==0 || pPg->needSync==0) ){
sqlite3OsSeek(&pPager->fd, (pgno-1)*(i64)pPager->pageSize);
rc = sqlite3OsWrite(&pPager->fd, aData, pPager->pageSize);
if( pPg ) pPg->dirty = 0;
}
if( pPg ){
/* No page should ever be explicitly rolled back that is in use, except
@@ -992,13 +1011,9 @@ static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int useCksum){
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;
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
pPg->pageHash = pager_pagehash(pPg);
#endif
}
CODEC(pPager, pData, pPg->pgno, 3);
}
return rc;