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Overview
| Comment: | Enhance sqlite3PcacheTruncate() to run faster in the common case where the cutoff is just a few pages less than the page number highwater mark. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | branch-3.14 |
| Files: | files | file ages | folders |
| SHA1: |
03dceaea15aa357097a4615ef6044be3 |
| User & Date: | drh 2016-08-11 13:03:51 |
Context
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2016-08-11
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| 13:08 | Increase the version number to 3.14.1. check-in: 34aed3a3 user: drh tags: branch-3.14 | |
| 13:03 | Enhance sqlite3PcacheTruncate() to run faster in the common case where the cutoff is just a few pages less than the page number highwater mark. check-in: 03dceaea user: drh tags: branch-3.14 | |
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2016-08-10
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| 15:02 | Tweaks to pcache1TruncateUnsafe() to make it slightly smaller and faster and easier to test. check-in: 059f4e2e user: drh tags: trunk | |
| 11:50 | Fix pcache1TruncateUnsafe() run faster for the case where iLimit is very close to iMaxKey. check-in: b07a26df user: drh tags: trunk | |
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2016-08-08
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| 13:40 | Version 3.14 check-in: d5e98057 user: drh tags: trunk, release, version-3.14.0 | |
Changes
Changes to src/pcache1.c.
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**
** The PCache mutex must be held when this function is called.
*/
static void pcache1TruncateUnsafe(
PCache1 *pCache, /* The cache to truncate */
unsigned int iLimit /* Drop pages with this pgno or larger */
){
TESTONLY( unsigned int nPage = 0; ) /* To assert pCache->nPage is correct */
unsigned int h;
assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
for(h=0; h<pCache->nHash; h++){
PgHdr1 **pp = &pCache->apHash[h];
PgHdr1 *pPage;
while( (pPage = *pp)!=0 ){
if( pPage->iKey>=iLimit ){
pCache->nPage--;
*pp = pPage->pNext;
if( !pPage->isPinned ) pcache1PinPage(pPage);
pcache1FreePage(pPage);
}else{
pp = &pPage->pNext;
TESTONLY( nPage++; )
}
}
}
assert( pCache->nPage==nPage );
}
/******************************************************************************/
/******** sqlite3_pcache Methods **********************************************/
/*
** Implementation of the sqlite3_pcache.xInit method.
................................................................................
** Destroy a cache allocated using pcache1Create().
*/
static void pcache1Destroy(sqlite3_pcache *p){
PCache1 *pCache = (PCache1 *)p;
PGroup *pGroup = pCache->pGroup;
assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
pcache1EnterMutex(pGroup);
pcache1TruncateUnsafe(pCache, 0);
assert( pGroup->nMaxPage >= pCache->nMax );
pGroup->nMaxPage -= pCache->nMax;
assert( pGroup->nMinPage >= pCache->nMin );
pGroup->nMinPage -= pCache->nMin;
pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
pcache1EnforceMaxPage(pCache);
pcache1LeaveMutex(pGroup);
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**
** The PCache mutex must be held when this function is called.
*/
static void pcache1TruncateUnsafe(
PCache1 *pCache, /* The cache to truncate */
unsigned int iLimit /* Drop pages with this pgno or larger */
){
TESTONLY( int nPage = 0; ) /* To assert pCache->nPage is correct */
unsigned int h, iStop;
assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
assert( pCache->iMaxKey >= iLimit );
assert( pCache->nHash > 0 );
if( pCache->iMaxKey - iLimit < pCache->nHash ){
/* If we are just shaving the last few pages off the end of the
** cache, then there is no point in scanning the entire hash table.
** Only scan those hash slots that might contain pages that need to
** be removed. */
h = iLimit % pCache->nHash;
iStop = pCache->iMaxKey % pCache->nHash;
TESTONLY( nPage = -10; ) /* Disable the pCache->nPage validity check */
}else{
/* This is the general case where many pages are being removed.
** It is necessary to scan the entire hash table */
h = pCache->nHash/2;
iStop = h - 1;
}
for(;;){
PgHdr1 **pp;
PgHdr1 *pPage;
assert( h<pCache->nHash );
pp = &pCache->apHash[h];
while( (pPage = *pp)!=0 ){
if( pPage->iKey>=iLimit ){
pCache->nPage--;
*pp = pPage->pNext;
if( !pPage->isPinned ) pcache1PinPage(pPage);
pcache1FreePage(pPage);
}else{
pp = &pPage->pNext;
TESTONLY( if( nPage>=0 ) nPage++; )
}
}
if( h==iStop ) break;
h = (h+1) % pCache->nHash;
}
assert( nPage<0 || pCache->nPage==(unsigned)nPage );
}
/******************************************************************************/
/******** sqlite3_pcache Methods **********************************************/
/*
** Implementation of the sqlite3_pcache.xInit method.
................................................................................
** Destroy a cache allocated using pcache1Create().
*/
static void pcache1Destroy(sqlite3_pcache *p){
PCache1 *pCache = (PCache1 *)p;
PGroup *pGroup = pCache->pGroup;
assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
pcache1EnterMutex(pGroup);
if( pCache->nPage ) pcache1TruncateUnsafe(pCache, 0);
assert( pGroup->nMaxPage >= pCache->nMax );
pGroup->nMaxPage -= pCache->nMax;
assert( pGroup->nMinPage >= pCache->nMin );
pGroup->nMinPage -= pCache->nMin;
pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
pcache1EnforceMaxPage(pCache);
pcache1LeaveMutex(pGroup);
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