/*
** Dereference a page. When the reference count reaches zero,
** move the page to the LRU list if it is clean.
*/
void sqlite3PcacheRelease(PgHdr *p) {
assert( p->nRef>0 );
p->nRef--;
if( p->nRef==0 ) {
PCache *pCache = p->pCache;
if( p->pCache->xDestroy ) {
p->pCache->xDestroy(p);
}
pCache->nRef--;
if( (p->flags&PGHDR_DIRTY)==0 ) {
pCache->nPinned--;
pcacheEnterMutex();
if( pcache.nCurrentPage>pcache.nMaxPage ) {
pcacheRemoveFromList(&pCache->pClean, p);
pcacheRemoveFromHash(p);
pcachePageFree(p);
} else {
pcacheAddToLruList(p);
}
pcacheExitMutex();
} else {
/* Move the page to the head of the caches dirty list. */
pcacheRemoveFromList(&pCache->pDirty, p);
pcacheAddToList(&pCache->pDirty, p);
}
}
}
static void pcacheMakeClean(PgHdr *p){
PCache *pCache = p->pCache;
assert( p->flags & PGHDR_DIRTY );
pcacheRemoveFromList(&pCache->pDirty, p);
pcacheAddToList(&pCache->pClean, p);
p->flags &= ~PGHDR_DIRTY;
if( p->nRef==0 ){
pcacheAddToLruList(p);
pCache->nPinned--;
}
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
}
/*
** Make sure the page is marked as dirty. If it isn't dirty already,
** make it so.
*/
void sqlite3PcacheMakeDirty(PgHdr *p){
PCache *pCache;
p->flags &= ~PGHDR_DONT_WRITE;
if( p->flags & PGHDR_DIRTY ) return;
assert( (p->flags & PGHDR_DIRTY)==0 );
assert( p->nRef>0 );
pCache = p->pCache;
pcacheEnterMutex();
pcacheRemoveFromList(&pCache->pClean, p);
pcacheAddToList(&pCache->pDirty, p);
pcacheExitMutex();
p->flags |= PGHDR_DIRTY;
}
/*
** Make every page in the cache clean.
*/
void sqlite3PcacheCleanAll(PCache *pCache){
PgHdr *p;
pcacheEnterMutex();
while( (p = pCache->pDirty)!=0 ){
pcacheRemoveFromList(&pCache->pDirty, p);
p->flags &= ~PGHDR_DIRTY;
pcacheAddToList(&pCache->pClean, p);
if( p->nRef==0 ){
pcacheAddToLruList(p);
pCache->nPinned--;
}
}
sqlite3PcacheAssertFlags(pCache, 0, PGHDR_DIRTY);
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
pcacheExitMutex();
}
/*
** Try to obtain a page from the cache.
*/
int sqlite3PcacheFetch(
PCache *pCache, /* Obtain the page from this cache */
Pgno pgno, /* Page number to obtain */
int createFlag, /* If true, create page if it does not exist already */
PgHdr **ppPage /* Write the page here */
){
int rc = SQLITE_OK;
PgHdr *pPage = 0;
assert( pcache_g.isInit );
assert( pCache!=0 );
assert( pgno>0 );
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
pcacheEnterMutex();
/* Search the hash table for the requested page. Exit early if it is found. */
if( pCache->apHash ){
u32 h = pgno % pCache->nHash;
for(pPage=pCache->apHash[h]; pPage; pPage=pPage->pNextHash){
if( pPage->pgno==pgno ){
if( pPage->nRef==0 ){
if( 0==(pPage->flags&PGHDR_DIRTY) ){
pcacheRemoveFromLruList(pPage);
pCache->nPinned++;
}
pCache->nRef++;
}
pPage->nRef++;
break;
}
}
}
if( !pPage && createFlag ){
if( pCache->nHash<=pCache->nPage ){
rc = pcacheResizeHash(pCache, pCache->nHash<256 ? 256 : pCache->nHash*2);
}
if( rc==SQLITE_OK ){
rc = pcacheRecycleOrAlloc(pCache, &pPage);
}
if( rc==SQLITE_OK ){
pPage->pPager = 0;
pPage->flags = 0;
pPage->pDirty = 0;
pPage->pgno = pgno;
pPage->pCache = pCache;
pPage->nRef = 1;
pCache->nRef++;
pCache->nPinned++;
pcacheAddToList(&pCache->pClean, pPage);
pcacheAddToHash(pPage);
}
}
pcacheExitMutex();
*ppPage = pPage;
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
assert( pPage || !createFlag || rc!=SQLITE_OK );
return rc;
}
