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Conjecture: a journal header with nRec==0 must be the last header in the

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journal.  Add asserts to make this conjecture explicit. (CVS 6132)

FossilOrigin-Name: 15b5b5f90c2ffa79155cdc2dbc4fb5583cb72017
This commit is contained in:
drh
2009-01-07 15:33:45 +00:00
parent f90b7260b3
commit ee03d629f5
4 changed files with 34 additions and 23 deletions
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32
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 1.538 2009/01/07 15:18:21 danielk1977 Exp $
** @(#) $Id: pager.c,v 1.539 2009/01/07 15:33:46 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
@@ -1315,7 +1315,7 @@ static int pager_playback_one_page(
return rc;
}
#if /* !defined(NDEBUG) || */ defined(SQLITE_COVERAGE_TEST)
#if !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST)
/*
** This routine looks ahead into the main journal file and determines
** whether or not the next record (the record that begins at file
@@ -1646,12 +1646,15 @@ static int pager_playback(Pager *pPager, int isHot){
** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
** the journal, it means that the journal might contain additional
** pages that need to be rolled back and that the number of pages
** should be computed based on the journal file size.
** should be computed based on the journal file size.
**
** 2009-01-07: We think #2565 is now unreachable due to changes
** in the pcache. The assert that follows will fire if we are wrong.
*/
testcase( nRec==0 && !isHot
assert( !(nRec==0 && !isHot
&& pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff
&& ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0
&& pagerNextJournalPageIsValid(pPager)
&& pagerNextJournalPageIsValid(pPager))
);
if( nRec==0 && !isHot &&
pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
@@ -1784,10 +1787,10 @@ static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
** test is related to ticket #2565. See the discussion in the
** pager_playback() function for additional information.
*/
testcase( nJRec==0
assert( !(nJRec==0
&& pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff
&& ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0
&& pagerNextJournalPageIsValid(pPager)
&& pagerNextJournalPageIsValid(pPager))
);
if( nJRec==0
&& pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
@@ -3574,18 +3577,27 @@ int sqlite3PagerWrite(DbPage *pDbPage){
}
}
/* If the PgHdr.needSync flag is set for any of the nPage pages
/* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages
** starting at pg1, then it needs to be set for all of them. Because
** writing to any of these nPage pages may damage the others, the
** journal file must contain sync()ed copies of all of them
** before any of them can be written out to the database file.
**
** 2009-01-07: This block of code appears to be a no-op. I do not
** believe it is possible for any page on the sector to not have
** the PGHDR_NEED_SYNC flag set. The "pPage->flags |= PGHDR_NEED_SYNC"
** line below does nothing, I think. But it does no harm to leave
** this code in place until we can definitively prove this is the case.
*/
if( needSync ){
assert( !MEMDB && pPager->noSync==0 );
for(ii=0; ii<nPage && needSync; ii++){
PgHdr *pPage = pager_lookup(pPager, pg1+ii);
if( pPage ) pPage->flags |= PGHDR_NEED_SYNC;
sqlite3PagerUnref(pPage);
if( pPage ){
assert( pPage->flags & PGHDR_NEED_SYNC ); /* 2009-01-07 conjecture */
pPage->flags |= PGHDR_NEED_SYNC;
sqlite3PagerUnref(pPage);
}
}
assert(pPager->needSync);
}