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Simplify the pcache by not keeping continuous track of page 1 but instead

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just loading page 1 on the rare occasions when it is actually needed.

FossilOrigin-Name: 015302f15e46a087ec92f3644c6741600dbf4306
This commit is contained in:
drh
2015-06-26 02:41:31 +00:00
parent 591909c344
commit 39065c60b3
3 changed files with 15 additions and 21 deletions
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22
src/pcache.c
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@@ -28,7 +28,6 @@ struct PCache {
int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */
void *pStress; /* Argument to xStress */
sqlite3_pcache *pCache; /* Pluggable cache module */
PgHdr *pPage1; /* Reference to page 1 */
};
/********************************** Linked List Management ********************/
@@ -106,9 +105,6 @@ static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){
*/
static void pcacheUnpin(PgHdr *p){
if( p->pCache->bPurgeable ){
if( p->pgno==1 ){
p->pCache->pPage1 = 0;
}
sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0);
}
}
@@ -201,7 +197,6 @@ int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
}
pCache->pCache = pNew;
pCache->pPage1 = 0;
pCache->szPage = szPage;
}
return SQLITE_OK;
@@ -359,9 +354,6 @@ PgHdr *sqlite3PcacheFetchFinish(
pCache->nRef++;
}
pPgHdr->nRef++;
if( pgno==1 ){
pCache->pPage1 = pPgHdr;
}
return pPgHdr;
}
@@ -402,9 +394,6 @@ void sqlite3PcacheDrop(PgHdr *p){
pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
}
p->pCache->nRef--;
if( p->pgno==1 ){
p->pCache->pPage1 = 0;
}
sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1);
}
@@ -495,9 +484,14 @@ void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
sqlite3PcacheMakeClean(p);
}
}
if( pgno==0 && pCache->pPage1 ){
memset(pCache->pPage1->pData, 0, pCache->szPage);
pgno = 1;
if( pgno==0 && pCache->nRef ){
sqlite3_pcache_page *pPage1;
pPage1 = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache,1,0);
if( ALWAYS(pPage1) ){ /* Page 1 is always available in cache, because
** pCache->nRef>0 */
memset(pPage1->pBuf, 0, pCache->szPage);
pgno = 1;
}
}
sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);
}