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Clarification of the pagerFlushOnCommit() logic.

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FossilOrigin-Name: 3401d9dcdbec390564574e8d2972c944c204e025
This commit is contained in:
drh
2016-05-13 12:12:38 +00:00
parent 935c4d8484
commit 4bf7d21f56
3 changed files with 22 additions and 18 deletions
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26
src/pager.c
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@@ -1876,20 +1876,24 @@ static int pager_error(Pager *pPager, int rc){
static int pager_truncate(Pager *pPager, Pgno nPage);
/*
** The write transaction open on the pager passed as the only argument is
** being committed. This function returns true if all dirty pages should
** be flushed to disk, or false otherwise. Pages should be flushed to disk
** unless one of the following is true:
** The write transaction open on pPager is being committed (bCommit==1)
** or rolled back (bCommit==0).
**
** * The db is an in-memory database.
** Return TRUE if and only if all dirty pages should be flushed to disk.
**
** * The db is a temporary database and the db file has not been opened.
** Rules:
**
** * The db is a temporary database and the cache contains less than
** C/4 dirty pages, where C is the configured cache-size.
** * For non-TEMP databases, always sync to disk. This is necessary
** for transactions to be durable.
**
** * Sync TEMP database only on a COMMIT (not a ROLLBACK) when the backing
** file has been created already (via a spill on pagerStress()) and
** when the number of dirty pages in memory exceeds 25% of the total
** cache size.
*/
static int pagerFlushOnCommit(Pager *pPager){
static int pagerFlushOnCommit(Pager *pPager, int bCommit){
if( pPager->tempFile==0 ) return 1;
if( !bCommit ) return 0;
if( !isOpen(pPager->fd) ) return 0;
return (sqlite3PCachePercentDirty(pPager->pPCache)>=25);
}
@@ -2033,7 +2037,7 @@ static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
pPager->pInJournal = 0;
pPager->nRec = 0;
if( rc==SQLITE_OK ){
if( !pPager->tempFile || (bCommit && pagerFlushOnCommit(pPager)) ){
if( pagerFlushOnCommit(pPager, bCommit) ){
sqlite3PcacheCleanAll(pPager->pPCache);
}else{
sqlite3PcacheClearWritable(pPager->pPCache);
@@ -6206,7 +6210,7 @@ int sqlite3PagerCommitPhaseOne(
assert( MEMDB==0 || pPager->tempFile );
assert( isOpen(pPager->fd) || pPager->tempFile );
if( 0==pagerFlushOnCommit(pPager) ){
if( 0==pagerFlushOnCommit(pPager, 1) ){
/* If this is an in-memory db, or no pages have been written to, or this
** function has already been called, it is mostly a no-op. However, any
** backup in progress needs to be restarted. */