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Disable memory-pressure induced cache spill during savepoint rollback.

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FossilOrigin-Name: a55eb4c3e9fa4ea43b8f8182eb9e39138df03f52
This commit is contained in:
drh
2010-06-24 14:52:25 +00:00
parent 0a6052ec51
commit 7cf4c7adf0
3 changed files with 45 additions and 35 deletions
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54
src/pager.c
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@@ -305,12 +305,13 @@ struct PagerSavepoint {
** master journal name is only written to the journal file the first
** time CommitPhaseOne() is called.
**
** doNotSync
** doNotSpill
**
** When enabled, cache spills are prohibited and the journal file cannot
** be synced. This variable is set and cleared by sqlite3PagerWrite()
** in order to prevent a journal sync from happening in between the
** journalling of two pages on the same sector.
** journalling of two pages on the same sector. It is also set to prevent
** pagerStress() from trying to use the journal during a rollback.
**
** needSync
**
@@ -354,7 +355,7 @@ struct Pager {
u8 journalStarted; /* True if header of journal is synced */
u8 changeCountDone; /* Set after incrementing the change-counter */
u8 setMaster; /* True if a m-j name has been written to jrnl */
u8 doNotSync; /* Boolean. While true, do not spill the cache */
u8 doNotSpill; /* Do not spill the cache when non-zero */
u8 dbSizeValid; /* Set when dbSize is correct */
u8 subjInMemory; /* True to use in-memory sub-journals */
Pgno dbSize; /* Number of pages in the database */
@@ -1690,9 +1691,12 @@ static int pager_playback_one_page(
** requiring a journal-sync before it is written.
*/
assert( isSavepnt );
if( (rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1))!=SQLITE_OK ){
return rc;
}
assert( pPager->doNotSpill==0 );
pPager->doNotSpill++;
rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1);
assert( pPager->doNotSpill==1 );
pPager->doNotSpill--;
if( rc!=SQLITE_OK ) return rc;
pPg->flags &= ~PGHDR_NEED_READ;
sqlite3PcacheMakeDirty(pPg);
}
@@ -3514,6 +3518,18 @@ static int pagerStress(void *p, PgHdr *pPg){
assert( pPg->pPager==pPager );
assert( pPg->flags&PGHDR_DIRTY );
/* The doNotSpill flag is set during times when writing to the journal
** is disallowed: (1) during calls to sqlite3PagerWrite() while it
** is journalling a set of two or more database pages that are stored
** on the same disk sector, and (2) while performing a rollback.
**
** Similarly, if the pager has already entered the error state, do not
** try to write the contents of pPg to disk.
*/
if( pPager->errCode || pPager->doNotSpill ){
return SQLITE_OK;
}
pPg->pDirty = 0;
if( pagerUseWal(pPager) ){
/* Write a single frame for this page to the log. */
@@ -3524,22 +3540,6 @@ static int pagerStress(void *p, PgHdr *pPg){
rc = pagerWalFrames(pPager, pPg, 0, 0, 0);
}
}else{
/* The doNotSync flag is set by the sqlite3PagerWrite() function while it
** is journalling a set of two or more database pages that are stored
** on the same disk sector. Syncing the journal is not allowed while
** this is happening as it is important that all members of such a
** set of pages are synced to disk together. So, if the page this function
** is trying to make clean will require a journal sync and the doNotSync
** flag is set, return without doing anything. The pcache layer will
** just have to go ahead and allocate a new page buffer instead of
** reusing pPg.
**
** Similarly, if the pager has already entered the error state, do not
** try to write the contents of pPg to disk.
*/
if( pPager->errCode || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC) ){
return SQLITE_OK;
}
/* Sync the journal file if required. */
if( pPg->flags&PGHDR_NEED_SYNC ){
@@ -4834,12 +4834,12 @@ int sqlite3PagerWrite(DbPage *pDbPage){
int ii; /* Loop counter */
int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */
/* Set the doNotSync flag to 1. This is because we cannot allow a journal
/* Set the doNotSpill flag to 1. This is because we cannot allow a journal
** header to be written between the pages journaled by this function.
*/
assert( !MEMDB );
assert( pPager->doNotSync==0 );
pPager->doNotSync = 1;
assert( pPager->doNotSpill==0 );
pPager->doNotSpill++;
/* This trick assumes that both the page-size and sector-size are
** an integer power of 2. It sets variable pg1 to the identifier
@@ -4901,8 +4901,8 @@ int sqlite3PagerWrite(DbPage *pDbPage){
assert(pPager->needSync);
}
assert( pPager->doNotSync==1 );
pPager->doNotSync = 0;
assert( pPager->doNotSpill==1 );
pPager->doNotSpill--;
}else{
rc = pager_write(pDbPage);
}