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Create a new pager type, PAGER_SORTER, for use in the external merge sort.

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Such pagers are always held in memory but do report when they are under
memory pressure by calling pagerStress.

FossilOrigin-Name: c71d73201d950355862dd8d5de142c9673888755
This commit is contained in:
drh
2011-08-26 00:34:45 +00:00
parent c5dbffe741
commit 2a5d9908f9
9 changed files with 76 additions and 19 deletions
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30
src/pager.c
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@@ -620,6 +620,8 @@ struct Pager {
u8 tempFile; /* zFilename is a temporary file */
u8 readOnly; /* True for a read-only database */
u8 memDb; /* True to inhibit all file I/O */
u8 hasSeenStress; /* pagerStress() called one or more times */
u8 isSorter; /* True for a PAGER_SORTER */
/**************************************************************************
** The following block contains those class members that change during
@@ -843,6 +845,15 @@ static int assert_pager_state(Pager *p){
assert( pagerUseWal(p)==0 );
}
/* A sorter is a temp file that never spills to disk and always has
** the doNotSpill flag set
*/
if( p->isSorter ){
assert( p->tempFile );
assert( p->doNotSpill );
assert( p->fd->pMethods==0 );
}
/* If changeCountDone is set, a RESERVED lock or greater must be held
** on the file.
*/
@@ -3739,6 +3750,7 @@ static int pagerSyncHotJournal(Pager *pPager){
int sqlite3PagerClose(Pager *pPager){
u8 *pTmp = (u8 *)pPager->pTmpSpace;
assert( assert_pager_state(pPager) );
disable_simulated_io_errors();
sqlite3BeginBenignMalloc();
/* pPager->errCode = 0; */
@@ -4173,6 +4185,7 @@ static int pagerStress(void *p, PgHdr *pPg){
** be called in the error state. Nevertheless, we include a NEVER()
** test for the error state as a safeguard against future changes.
*/
pPager->hasSeenStress = 1;
if( NEVER(pPager->errCode) ) return SQLITE_OK;
if( pPager->doNotSpill ) return SQLITE_OK;
if( pPager->doNotSyncSpill && (pPg->flags & PGHDR_NEED_SYNC)!=0 ){
@@ -4544,6 +4557,12 @@ int sqlite3PagerOpen(
/* pPager->pBusyHandlerArg = 0; */
pPager->xReiniter = xReinit;
/* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
#ifndef SQLITE_OMIT_MERGE_SORT
if( flags & PAGER_SORTER ){
pPager->doNotSpill = 1;
pPager->isSorter = 1;
}
#endif
*ppPager = pPager;
return SQLITE_OK;
@@ -6088,6 +6107,17 @@ int sqlite3PagerIsMemdb(Pager *pPager){
return MEMDB;
}
#ifndef SQLITE_OMIT_MERGE_SORT
/*
** Return true if the pager has seen a pagerStress callback.
*/
int sqlite3PagerUnderStress(Pager *pPager){
assert( pPager->isSorter );
assert( pPager->doNotSpill );
return pPager->hasSeenStress;
}
#endif
/*
** Check that there are at least nSavepoint savepoints open. If there are
** currently less than nSavepoints open, then open one or more savepoints