database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-08-07 02:42:48 +03:00
Code Activity

Add a complex assert() that checks a pager invariant. (CVS 6934)

Browse Source 
FossilOrigin-Name: 2e08ad7bf629485a79ccebcf4c413e9dcc0d3ccf
This commit is contained in:
danielk1977
2009-07-25 11:40:07 +00:00
parent 8a938f9808
commit 9f0b6be85c
3 changed files with 45 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
src/pager.c
View File

@@ -18,7 +18,7 @@
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.620 2009/07/25 04:12:02 drh Exp $
** @(#) $Id: pager.c,v 1.621 2009/07/25 11:40:08 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
@@ -2625,6 +2625,40 @@ static int pager_wait_on_lock(Pager *pPager, int locktype){
return rc;
}
/*
** Function assertTruncateConstraint(pPager) checks that one of the
** following is true for all dirty pages currently in the page-cache:
**
** a) The page number is less than or equal to the size of the
** current database image, in pages, OR
**
** b) if the page content were written at this time, it would not
** be necessary to write the current content out to the sub-journal
** (as determined by function subjRequiresPage()).
**
** If the condition asserted by this function were not true, and the
** dirty page were to be discarded from the cache via the pagerStress()
** routine, pagerStress() would not write the current page content to
** the database file. If a savepoint transaction were rolled back after
** this happened, the correct behaviour would be to restore the current
** content of the page. However, since this content is not present in either
** the database file or the portion of the rollback journal and
** sub-journal rolled back the content could not be restored and the
** database image would become corrupt. It is therefore fortunate that
** this circumstance cannot arise.
*/
#if defined(SQLITE_DEBUG)
static void assertTruncateConstraintCb(PgHdr *pPg){
assert( pPg->flags&PGHDR_DIRTY );
assert( !subjRequiresPage(pPg) || pPg->pgno<=pPg->pPager->dbSize );
}
static void assertTruncateConstraint(Pager *pPager){
sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb);
}
#else
# define assertTruncateConstraint(pPager)
#endif
/*
** Truncate the in-memory database file image to nPage pages. This
** function does not actually modify the database file on disk. It
@@ -2636,6 +2670,7 @@ void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
assert( pPager->dbSize>=nPage );
assert( pPager->state>=PAGER_RESERVED );
pPager->dbSize = nPage;
assertTruncateConstraint(pPager);
}
/*
@@ -4963,6 +4998,7 @@ int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
/* Open the sub-journal, if it is not already opened. */
rc = openSubJournal(pPager);
assertTruncateConstraint(pPager);
}
return rc;