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Add variable pager.dbHintSize, used to limit the number of calls made to the xFileControl(FCNTL_SIZE_HINT) method.

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FossilOrigin-Name: eb3ac895bd92c880ac6acca58de8cf9643c2b5e4
This commit is contained in:
dan
2010-08-10 09:58:57 +00:00
parent de5fd22f3d
commit c864912ad1
3 changed files with 47 additions and 44 deletions
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77
src/pager.c
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@@ -565,7 +565,30 @@ struct PagerSavepoint {
** Throughout a write-transaction, dbFileSize contains the size of
** the file on disk in pages. It is set to a copy of dbSize when the
** write-transaction is first opened, and updated when VFS calls are made
** to write or truncate the database file on disk.
** to write or truncate the database file on disk.
**
** The only reason the dbFileSize variable is required is to suppress
** unnecessary calls to xTruncate() after committing a transaction. If,
** when a transaction is committed, the dbFileSize variable indicates
** that the database file is larger than the database image (Pager.dbSize),
** pager_truncate() is called. The pager_truncate() call uses xFilesize()
** to measure the database file on disk, and then truncates it if required.
** dbFileSize is not used when rolling back a transaction. In this case
** pager_truncate() is called unconditionally (which means there may be
** a call to xFilesize() that is not strictly required). In either case,
** pager_truncate() may cause the file to become smaller or larger.
**
** dbHintSize
**
** The dbHintSize variable is used to limit the number of calls made to
** the VFS xFileControl(FCNTL_SIZE_HINT) method.
**
** dbHintSize is set to a copy of the dbSize variable when a
** write-transaction is opened (at the same time as dbFileSize and
** dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called,
** dbHintSize is increased to the number of pages that correspond to the
** size-hint passed to the method call. See pager_write_pagelist() for
** details.
**
** errCode
**
@@ -619,6 +642,7 @@ struct Pager {
Pgno dbSize; /* Number of pages in the database */
Pgno dbOrigSize; /* dbSize before the current transaction */
Pgno dbFileSize; /* Number of pages in the database file */
Pgno dbHintSize; /* Value passed to FCNTL_SIZE_HINT call */
int errCode; /* One of several kinds of errors */
int nRec; /* Pages journalled since last j-header written */
u32 cksumInit; /* Quasi-random value added to every checksum */
@@ -831,6 +855,7 @@ static int assert_pager_state(Pager *p){
}
assert( pPager->dbSize==pPager->dbOrigSize );
assert( pPager->dbOrigSize==pPager->dbFileSize );
assert( pPager->dbOrigSize==pPager->dbHintSize );
assert( pPager->setMaster==0 );
break;
@@ -850,6 +875,7 @@ static int assert_pager_state(Pager *p){
);
}
assert( pPager->dbOrigSize==pPager->dbFileSize );
assert( pPager->dbOrigSize==pPager->dbHintSize );
break;
case PAGER_WRITER_DBMOD:
@@ -861,6 +887,7 @@ static int assert_pager_state(Pager *p){
|| p->journalMode==PAGER_JOURNALMODE_OFF
|| p->journalMode==PAGER_JOURNALMODE_WAL
);
assert( pPager->dbOrigSize<=pPager->dbHintSize );
break;
case PAGER_WRITER_FINISHED:
@@ -3829,41 +3856,12 @@ static int syncJournal(Pager *pPager, int newHdr){
** be obtained, SQLITE_BUSY is returned.
*/
static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
int rc; /* Return code */
int rc = SQLITE_OK; /* Return code */
/* Normally, this function is called in WRITER_DBMOD state.
**
** However it may be called in WRITER_CACHEMOD state if the page being
** written (and all other pages that reside on the same disk sector) was
** a free-list leaf page at the start of the transaction. In that case
** the database file is not really being modified, so it is Ok to write
** to it in CACHEMOD state.
*/
/* This function is only called for rollback pagers in WRITER_DBMOD state. */
assert( !pagerUseWal(pPager) );
assert( pPager->eState==PAGER_WRITER_DBMOD
|| pPager->eState==PAGER_WRITER_CACHEMOD
);
assert( pPager->eState==PAGER_WRITER_DBMOD
|| (pList->pDirty==0 && pList->pgno<=pPager->dbFileSize)
);
/* At this point there may be either a RESERVED or EXCLUSIVE lock on the
** database file. If there is already an EXCLUSIVE lock, the following
** call is a no-op.
**
** Moving the lock from RESERVED to EXCLUSIVE actually involves going
** through an intermediate state PENDING. A PENDING lock prevents new
** readers from attaching to the database but is unsufficient for us to
** write. The idea of a PENDING lock is to prevent new readers from
** coming in while we wait for existing readers to clear.
**
** While the pager is in the RESERVED state, the original database file
** is unchanged and we can rollback without having to playback the
** journal into the original database file. Once we transition to
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
assert( pPager->eState==PAGER_WRITER_DBMOD );
assert( pPager->eLock==EXCLUSIVE_LOCK );
/* If the file is a temp-file has not yet been opened, open it now. It
** is not possible for rc to be other than SQLITE_OK if this branch
@@ -3878,9 +3876,10 @@ static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
** file size will be.
*/
assert( rc!=SQLITE_OK || isOpen(pPager->fd) );
if( rc==SQLITE_OK && pPager->dbSize>pPager->dbOrigSize ){
if( rc==SQLITE_OK && pPager->dbSize>pPager->dbHintSize ){
sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
pPager->dbHintSize = pPager->dbSize;
}
while( rc==SQLITE_OK && pList ){
@@ -4062,7 +4061,9 @@ static int pagerStress(void *p, PgHdr *pPg){
}else{
/* Sync the journal file if required. */
if( pPg->flags&PGHDR_NEED_SYNC ){
if( pPg->flags&PGHDR_NEED_SYNC
|| pPager->eState==PAGER_WRITER_CACHEMOD
){
rc = syncJournal(pPager, 1);
}
@@ -5124,7 +5125,9 @@ int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
** WAL mode.
*/
pPager->eState = PAGER_WRITER_LOCKED;
pPager->dbFileSize = pPager->dbOrigSize = pPager->dbSize;
pPager->dbHintSize = pPager->dbSize;
pPager->dbFileSize = pPager->dbSize;
pPager->dbOrigSize = pPager->dbSize;
pPager->journalOff = 0;
}