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Size and performance optimization the readDbPage() routine in the pager.

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FossilOrigin-Name: ca9e1875c3a893321d70a131fc4ffc76d169ad05e0b48b7006f53b6b467db4be
This commit is contained in:
drh
2017-08-18 21:14:50 +00:00
parent c68886bb9e
commit 56520ab848
3 changed files with 18 additions and 25 deletions
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29
src/pager.c
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@@ -2982,7 +2982,8 @@ end_playback:
/*
** Read the content for page pPg out of the database file and into
** Read the content for page pPg out of the database file (or out of
** the WAL if that is where the most recent copy if found) into
** pPg->pData. A shared lock or greater must be held on the database
** file before this function is called.
**
@@ -2992,22 +2993,23 @@ end_playback:
** If an IO error occurs, then the IO error is returned to the caller.
** Otherwise, SQLITE_OK is returned.
*/
static int readDbPage(PgHdr *pPg, u32 iFrame){
static int readDbPage(PgHdr *pPg){
Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
Pgno pgno = pPg->pgno; /* Page number to read */
int rc = SQLITE_OK; /* Return code */
int pgsz = pPager->pageSize; /* Number of bytes to read */
u32 iFrame = 0; /* Frame of WAL containing pgno */
assert( pPager->eState>=PAGER_READER && !MEMDB );
assert( isOpen(pPager->fd) );
#ifndef SQLITE_OMIT_WAL
if( pagerUseWal(pPager) ){
rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
if( rc ) return rc;
}
if( iFrame ){
/* Try to pull the page from the write-ahead log. */
rc = sqlite3WalReadFrame(pPager->pWal, iFrame, pgsz, pPg->pData);
}else
#endif
{
}else{
i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
if( rc==SQLITE_IOERR_SHORT_READ ){
@@ -3092,11 +3094,7 @@ static int pagerUndoCallback(void *pCtx, Pgno iPg){
if( sqlite3PcachePageRefcount(pPg)==1 ){
sqlite3PcacheDrop(pPg);
}else{
u32 iFrame = 0;
rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame);
if( rc==SQLITE_OK ){
rc = readDbPage(pPg, iFrame);
}
rc = readDbPage(pPg);
if( rc==SQLITE_OK ){
pPager->xReiniter(pPg);
}
@@ -5489,14 +5487,9 @@ static int getPageNormal(
memset(pPg->pData, 0, pPager->pageSize);
IOTRACE(("ZERO %p %d\n", pPager, pgno));
}else{
u32 iFrame = 0; /* Frame to read from WAL file */
if( pagerUseWal(pPager) ){
rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
if( rc!=SQLITE_OK ) goto pager_acquire_err;
}
assert( pPg->pPager==pPager );
pPager->aStat[PAGER_STAT_MISS]++;
rc = readDbPage(pPg, iFrame);
rc = readDbPage(pPg);
if( rc!=SQLITE_OK ){
goto pager_acquire_err;
}