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https://github.com/sqlite/sqlite.git
synced 2025-08-07 02:42:48 +03:00
Refactoring the btree and pager routines into distinct two-phase commit
routines. We've always done a two-phase commit - this change is just making that more apparent in the code. (CVS 3762) FossilOrigin-Name: 66b3ad09ea657d25d48cb75ec2671ea2dc1b6005
This commit is contained in:
drh
298
src/pager.c
298
src/pager.c
@@ -18,7 +18,7 @@
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** file simultaneously, or one process from reading the database while
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** another is writing.
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**
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** @(#) $Id: pager.c,v 1.306 2007/03/29 18:19:52 drh Exp $
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** @(#) $Id: pager.c,v 1.307 2007/03/30 14:06:34 drh Exp $
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*/
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#ifndef SQLITE_OMIT_DISKIO
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#include "sqliteInt.h"
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@@ -160,7 +160,7 @@ struct PgHdr {
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u8 inStmt; /* TRUE if in the statement subjournal */
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u8 dirty; /* TRUE if we need to write back changes */
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u8 needSync; /* Sync journal before writing this page */
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u8 alwaysRollback; /* Disable dont_rollback() for this page */
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u8 alwaysRollback; /* Disable DontRollback() for this page */
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short int nRef; /* Number of users of this page */
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PgHdr *pDirty, *pPrevDirty; /* Dirty pages */
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u32 notUsed; /* Buffer space */
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@@ -236,9 +236,12 @@ struct Pager {
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u8 readOnly; /* True for a read-only database */
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u8 needSync; /* True if an fsync() is needed on the journal */
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u8 dirtyCache; /* True if cached pages have changed */
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u8 alwaysRollback; /* Disable dont_rollback() for all pages */
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u8 alwaysRollback; /* Disable DontRollback() for all pages */
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u8 memDb; /* True to inhibit all file I/O */
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u8 setMaster; /* True if a m-j name has been written to jrnl */
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u8 doNotSync; /* Boolean. While true, do not spill the cache */
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u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
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u8 changeCountDone; /* Set after incrementing the change-counter */
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int errCode; /* One of several kinds of errors */
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int dbSize; /* Number of pages in the file */
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int origDbSize; /* dbSize before the current change */
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@@ -286,9 +289,6 @@ struct Pager {
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#endif
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char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */
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u32 iChangeCount; /* Db change-counter for which cache is valid */
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u8 doNotSync; /* Boolean. While true, do not spill the cache */
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u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
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u8 changeCountDone; /* Set after incrementing the change-counter */
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};
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/*
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@@ -910,16 +910,23 @@ static void pager_reset(Pager *pPager){
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}
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/*
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** This routine ends a transaction. A transaction is ended by either
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** a COMMIT or a ROLLBACK.
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**
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** When this routine is called, the pager has the journal file open and
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** a RESERVED or EXCLUSIVE lock on the database. This routine releases
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** the database lock and acquires a SHARED lock in its place. The journal
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** file is deleted and closed.
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** a RESERVED or EXCLUSIVE lock on the database. This routine will release
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** the database lock and acquires a SHARED lock in its place if that is
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** the appropriate thing to do. Release locks usually is appropriate,
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** unless we are in exclusive access mode or unless this is a
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** COMMIT AND BEGIN or ROLLBACK AND BEGIN operation.
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**
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** The journal file is either deleted or truncated.
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**
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** TODO: Consider keeping the journal file open for temporary databases.
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** This might give a performance improvement on windows where opening
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** a file is an expensive operation.
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*/
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static int pager_unwritelock(Pager *pPager){
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static int pager_end_transaction(Pager *pPager){
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PgHdr *pPg;
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int rc = SQLITE_OK;
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int rc2 = SQLITE_OK;
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@@ -1423,7 +1430,7 @@ static int pager_playback(Pager *pPager, int isHot){
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end_playback:
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if( rc==SQLITE_OK ){
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rc = pager_unwritelock(pPager);
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rc = pager_end_transaction(pPager);
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}
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if( zMaster ){
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/* If there was a master journal and this routine will return success,
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@@ -2563,7 +2570,7 @@ static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
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/* If the page we are recycling is marked as alwaysRollback, then
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** set the global alwaysRollback flag, thus disabling the
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** sqlite_dont_rollback() optimization for the rest of this transaction.
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** sqlite3PagerDontRollback() optimization for the rest of this transaction.
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** It is necessary to do this because the page marked alwaysRollback
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** might be reloaded at a later time but at that point we won't remember
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** that is was marked alwaysRollback. This means that all pages must
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@@ -3096,7 +3103,7 @@ static int pager_open_journal(Pager *pPager){
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rc = sqlite3PagerStmtBegin(pPager);
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}
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if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM ){
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rc = pager_unwritelock(pPager);
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rc = pager_end_transaction(pPager);
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if( rc==SQLITE_OK ){
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rc = SQLITE_FULL;
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}
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@@ -3127,7 +3134,7 @@ failed_to_open_journal:
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** Acquire a write-lock on the database. The lock is removed when
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** the any of the following happen:
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**
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** * sqlite3PagerCommit() is called.
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** * sqlite3PagerCommitPhaseTwo() is called.
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** * sqlite3PagerRollback() is called.
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** * sqlite3PagerClose() is called.
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** * sqlite3PagerUnref() is called to on every outstanding page.
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@@ -3528,9 +3535,9 @@ int sqlite3PagerOverwrite(Pager *pPager, Pgno pgno, void *pData){
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** a transaction then removed from the freelist during a later part
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** of the same transaction and reused for some other purpose. When it
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** is first added to the freelist, this routine is called. When reused,
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** the dont_rollback() routine is called. But because the page contains
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** critical data, we still need to be sure it gets rolled back in spite
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** of the dont_rollback() call.
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** the sqlite3PagerDontRollback() routine is called. But because the
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** page contains critical data, we still need to be sure it gets
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** rolled back in spite of the sqlite3PagerDontRollback() call.
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*/
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void sqlite3PagerDontWrite(Pager *pPager, Pgno pgno){
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PgHdr *pPg;
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@@ -3594,6 +3601,129 @@ void sqlite3PagerDontRollback(DbPage *pPg){
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}
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/*
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** This routine is called to increment the database file change-counter,
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** stored at byte 24 of the pager file.
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*/
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static int pager_incr_changecounter(Pager *pPager){
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PgHdr *pPgHdr;
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u32 change_counter;
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int rc;
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if( !pPager->changeCountDone ){
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/* Open page 1 of the file for writing. */
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rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
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if( rc!=SQLITE_OK ) return rc;
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rc = sqlite3PagerWrite(pPgHdr);
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if( rc!=SQLITE_OK ) return rc;
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/* Read the current value at byte 24. */
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change_counter = retrieve32bits(pPgHdr, 24);
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/* Increment the value just read and write it back to byte 24. */
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change_counter++;
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put32bits(((char*)PGHDR_TO_DATA(pPgHdr))+24, change_counter);
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pPager->iChangeCount = change_counter;
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/* Release the page reference. */
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sqlite3PagerUnref(pPgHdr);
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pPager->changeCountDone = 1;
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}
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return SQLITE_OK;
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}
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/*
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** Sync the database file for the pager pPager. zMaster points to the name
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** of a master journal file that should be written into the individual
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** journal file. zMaster may be NULL, which is interpreted as no master
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** journal (a single database transaction).
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**
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** This routine ensures that the journal is synced, all dirty pages written
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** to the database file and the database file synced. The only thing that
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** remains to commit the transaction is to delete the journal file (or
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** master journal file if specified).
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**
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** Note that if zMaster==NULL, this does not overwrite a previous value
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** passed to an sqlite3PagerCommitPhaseOne() call.
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**
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** If parameter nTrunc is non-zero, then the pager file is truncated to
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** nTrunc pages (this is used by auto-vacuum databases).
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*/
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int sqlite3PagerCommitPhaseOne(Pager *pPager, const char *zMaster, Pgno nTrunc){
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int rc = SQLITE_OK;
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PAGERTRACE4("DATABASE SYNC: File=%s zMaster=%s nTrunc=%d\n",
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pPager->zFilename, zMaster, nTrunc);
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/* If this is an in-memory db, or no pages have been written to, or this
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** function has already been called, it is a no-op.
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*/
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if( pPager->state!=PAGER_SYNCED && !MEMDB && pPager->dirtyCache ){
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PgHdr *pPg;
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assert( pPager->journalOpen );
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/* If a master journal file name has already been written to the
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** journal file, then no sync is required. This happens when it is
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** written, then the process fails to upgrade from a RESERVED to an
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** EXCLUSIVE lock. The next time the process tries to commit the
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** transaction the m-j name will have already been written.
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*/
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if( !pPager->setMaster ){
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rc = pager_incr_changecounter(pPager);
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if( rc!=SQLITE_OK ) goto sync_exit;
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#ifndef SQLITE_OMIT_AUTOVACUUM
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if( nTrunc!=0 ){
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/* If this transaction has made the database smaller, then all pages
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** being discarded by the truncation must be written to the journal
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** file.
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*/
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Pgno i;
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int iSkip = PAGER_MJ_PGNO(pPager);
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for( i=nTrunc+1; i<=pPager->origDbSize; i++ ){
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if( !(pPager->aInJournal[i/8] & (1<<(i&7))) && i!=iSkip ){
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rc = sqlite3PagerGet(pPager, i, &pPg);
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if( rc!=SQLITE_OK ) goto sync_exit;
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rc = sqlite3PagerWrite(pPg);
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sqlite3PagerUnref(pPg);
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if( rc!=SQLITE_OK ) goto sync_exit;
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}
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}
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}
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#endif
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rc = writeMasterJournal(pPager, zMaster);
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if( rc!=SQLITE_OK ) goto sync_exit;
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rc = syncJournal(pPager);
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if( rc!=SQLITE_OK ) goto sync_exit;
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}
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#ifndef SQLITE_OMIT_AUTOVACUUM
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if( nTrunc!=0 ){
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rc = sqlite3PagerTruncate(pPager, nTrunc);
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if( rc!=SQLITE_OK ) goto sync_exit;
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}
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#endif
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/* Write all dirty pages to the database file */
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pPg = pager_get_all_dirty_pages(pPager);
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rc = pager_write_pagelist(pPg);
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if( rc!=SQLITE_OK ) goto sync_exit;
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/* Sync the database file. */
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if( !pPager->noSync ){
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rc = sqlite3OsSync(pPager->fd, 0);
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}
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IOTRACE(("DBSYNC %p\n", pPager))
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pPager->state = PAGER_SYNCED;
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}else if( MEMDB && nTrunc!=0 ){
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rc = sqlite3PagerTruncate(pPager, nTrunc);
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}
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sync_exit:
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return rc;
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}
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/*
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** Commit all changes to the database and release the write lock.
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**
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@@ -3601,7 +3731,7 @@ void sqlite3PagerDontRollback(DbPage *pPg){
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** and an error code is returned. If the commit worked, SQLITE_OK
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** is returned.
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*/
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int sqlite3PagerCommit(Pager *pPager){
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int sqlite3PagerCommitPhaseTwo(Pager *pPager){
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int rc;
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PgHdr *pPg;
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@@ -3640,12 +3770,12 @@ int sqlite3PagerCommit(Pager *pPager){
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/* Exit early (without doing the time-consuming sqlite3OsSync() calls)
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** if there have been no changes to the database file. */
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assert( pPager->needSync==0 );
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rc = pager_unwritelock(pPager);
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rc = pager_end_transaction(pPager);
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}else{
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assert( pPager->journalOpen );
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rc = sqlite3PagerSync(pPager, 0, 0);
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rc = sqlite3PagerCommitPhaseOne(pPager, 0, 0);
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if( rc==SQLITE_OK ){
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rc = pager_unwritelock(pPager);
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rc = pager_end_transaction(pPager);
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}
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}
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return pager_error(pPager, rc);
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@@ -3703,7 +3833,7 @@ int sqlite3PagerRollback(Pager *pPager){
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}
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if( !pPager->dirtyCache || !pPager->journalOpen ){
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rc = pager_unwritelock(pPager);
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rc = pager_end_transaction(pPager);
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return rc;
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}
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@@ -3716,7 +3846,7 @@ int sqlite3PagerRollback(Pager *pPager){
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if( pPager->state==PAGER_RESERVED ){
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int rc2;
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rc = pager_playback(pPager, 0);
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rc2 = pager_unwritelock(pPager);
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rc2 = pager_end_transaction(pPager);
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if( rc==SQLITE_OK ){
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rc = rc2;
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}
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@@ -3926,128 +4056,6 @@ void sqlite3PagerSetCodec(
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pPager->pCodecArg = pCodecArg;
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}
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/*
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** This routine is called to increment the database file change-counter,
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** stored at byte 24 of the pager file.
|
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*/
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static int pager_incr_changecounter(Pager *pPager){
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PgHdr *pPgHdr;
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u32 change_counter;
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int rc;
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if( !pPager->changeCountDone ){
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/* Open page 1 of the file for writing. */
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rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
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if( rc!=SQLITE_OK ) return rc;
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rc = sqlite3PagerWrite(pPgHdr);
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if( rc!=SQLITE_OK ) return rc;
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|
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/* Read the current value at byte 24. */
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change_counter = retrieve32bits(pPgHdr, 24);
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|
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/* Increment the value just read and write it back to byte 24. */
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change_counter++;
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put32bits(((char*)PGHDR_TO_DATA(pPgHdr))+24, change_counter);
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pPager->iChangeCount = change_counter;
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|
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/* Release the page reference. */
|
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sqlite3PagerUnref(pPgHdr);
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pPager->changeCountDone = 1;
|
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}
|
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return SQLITE_OK;
|
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}
|
||||
|
||||
/*
|
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** Sync the database file for the pager pPager. zMaster points to the name
|
||||
** of a master journal file that should be written into the individual
|
||||
** journal file. zMaster may be NULL, which is interpreted as no master
|
||||
** journal (a single database transaction).
|
||||
**
|
||||
** This routine ensures that the journal is synced, all dirty pages written
|
||||
** to the database file and the database file synced. The only thing that
|
||||
** remains to commit the transaction is to delete the journal file (or
|
||||
** master journal file if specified).
|
||||
**
|
||||
** Note that if zMaster==NULL, this does not overwrite a previous value
|
||||
** passed to an sqlite3PagerSync() call.
|
||||
**
|
||||
** If parameter nTrunc is non-zero, then the pager file is truncated to
|
||||
** nTrunc pages (this is used by auto-vacuum databases).
|
||||
*/
|
||||
int sqlite3PagerSync(Pager *pPager, const char *zMaster, Pgno nTrunc){
|
||||
int rc = SQLITE_OK;
|
||||
|
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PAGERTRACE4("DATABASE SYNC: File=%s zMaster=%s nTrunc=%d\n",
|
||||
pPager->zFilename, zMaster, nTrunc);
|
||||
|
||||
/* If this is an in-memory db, or no pages have been written to, or this
|
||||
** function has already been called, it is a no-op.
|
||||
*/
|
||||
if( pPager->state!=PAGER_SYNCED && !MEMDB && pPager->dirtyCache ){
|
||||
PgHdr *pPg;
|
||||
assert( pPager->journalOpen );
|
||||
|
||||
/* If a master journal file name has already been written to the
|
||||
** journal file, then no sync is required. This happens when it is
|
||||
** written, then the process fails to upgrade from a RESERVED to an
|
||||
** EXCLUSIVE lock. The next time the process tries to commit the
|
||||
** transaction the m-j name will have already been written.
|
||||
*/
|
||||
if( !pPager->setMaster ){
|
||||
rc = pager_incr_changecounter(pPager);
|
||||
if( rc!=SQLITE_OK ) goto sync_exit;
|
||||
#ifndef SQLITE_OMIT_AUTOVACUUM
|
||||
if( nTrunc!=0 ){
|
||||
/* If this transaction has made the database smaller, then all pages
|
||||
** being discarded by the truncation must be written to the journal
|
||||
** file.
|
||||
*/
|
||||
Pgno i;
|
||||
int iSkip = PAGER_MJ_PGNO(pPager);
|
||||
for( i=nTrunc+1; i<=pPager->origDbSize; i++ ){
|
||||
if( !(pPager->aInJournal[i/8] & (1<<(i&7))) && i!=iSkip ){
|
||||
rc = sqlite3PagerGet(pPager, i, &pPg);
|
||||
if( rc!=SQLITE_OK ) goto sync_exit;
|
||||
rc = sqlite3PagerWrite(pPg);
|
||||
sqlite3PagerUnref(pPg);
|
||||
if( rc!=SQLITE_OK ) goto sync_exit;
|
||||
}
|
||||
}
|
||||
}
|
||||
#endif
|
||||
rc = writeMasterJournal(pPager, zMaster);
|
||||
if( rc!=SQLITE_OK ) goto sync_exit;
|
||||
rc = syncJournal(pPager);
|
||||
if( rc!=SQLITE_OK ) goto sync_exit;
|
||||
}
|
||||
|
||||
#ifndef SQLITE_OMIT_AUTOVACUUM
|
||||
if( nTrunc!=0 ){
|
||||
rc = sqlite3PagerTruncate(pPager, nTrunc);
|
||||
if( rc!=SQLITE_OK ) goto sync_exit;
|
||||
}
|
||||
#endif
|
||||
|
||||
/* Write all dirty pages to the database file */
|
||||
pPg = pager_get_all_dirty_pages(pPager);
|
||||
rc = pager_write_pagelist(pPg);
|
||||
if( rc!=SQLITE_OK ) goto sync_exit;
|
||||
|
||||
/* Sync the database file. */
|
||||
if( !pPager->noSync ){
|
||||
rc = sqlite3OsSync(pPager->fd, 0);
|
||||
}
|
||||
IOTRACE(("DBSYNC %p\n", pPager))
|
||||
|
||||
pPager->state = PAGER_SYNCED;
|
||||
}else if( MEMDB && nTrunc!=0 ){
|
||||
rc = sqlite3PagerTruncate(pPager, nTrunc);
|
||||
}
|
||||
|
||||
sync_exit:
|
||||
return rc;
|
||||
}
|
||||
|
||||
#ifndef SQLITE_OMIT_AUTOVACUUM
|
||||
/*
|
||||
** Move the page identified by pData to location pgno in the file.
|
||||
|
||||
Reference in New Issue
Block a user