xact.c

postgresql8.3.4源码,开源数据库

	 * GID is invalid or already in use.
	 */
	gxact = MarkAsPreparing(xid, prepareGID, prepared_at,
							GetUserId(), MyDatabaseId);
	prepareGID = NULL;

	/*
	 * Collect data for the 2PC state file.  Note that in general, no actual
	 * state change should happen in the called modules during this step,
	 * since it's still possible to fail before commit, and in that case we
	 * want transaction abort to be able to clean up.  (In particular, the
	 * AtPrepare routines may error out if they find cases they cannot
	 * handle.)  State cleanup should happen in the PostPrepare routines
	 * below.  However, some modules can go ahead and clear state here because
	 * they wouldn't do anything with it during abort anyway.
	 *
	 * Note: because the 2PC state file records will be replayed in the same
	 * order they are made, the order of these calls has to match the order in
	 * which we want things to happen during COMMIT PREPARED or ROLLBACK
	 * PREPARED; in particular, pay attention to whether things should happen
	 * before or after releasing the transaction's locks.
	 */
	StartPrepare(gxact);

	AtPrepare_Notify();
	AtPrepare_UpdateFlatFiles();
	AtPrepare_Inval();
	AtPrepare_Locks();
	AtPrepare_PgStat();

	/*
	 * Here is where we really truly prepare.
	 *
	 * We have to record transaction prepares even if we didn't make any
	 * updates, because the transaction manager might get confused if we lose
	 * a global transaction.
	 */
	EndPrepare(gxact);

	/*
	 * Now we clean up backend-internal state and release internal resources.
	 */

	/* Reset XactLastRecEnd until the next transaction writes something */
	XactLastRecEnd.xrecoff = 0;

	/*
	 * Let others know about no transaction in progress by me.	This has to be
	 * done *after* the prepared transaction has been marked valid, else
	 * someone may think it is unlocked and recyclable.
	 */
	ProcArrayClearTransaction(MyProc);

	/*
	 * This is all post-transaction cleanup.  Note that if an error is raised
	 * here, it's too late to abort the transaction.  This should be just
	 * noncritical resource releasing.	See notes in CommitTransaction.
	 */

	CallXactCallbacks(XACT_EVENT_PREPARE);

	ResourceOwnerRelease(TopTransactionResourceOwner,
						 RESOURCE_RELEASE_BEFORE_LOCKS,
						 true, true);

	/* Check we've released all buffer pins */
	AtEOXact_Buffers(true);

	/* Clean up the relation cache */
	AtEOXact_RelationCache(true);

	/* notify and flatfiles don't need a postprepare call */

	PostPrepare_PgStat();

	PostPrepare_Inval();

	PostPrepare_smgr();

	AtEOXact_MultiXact();

	PostPrepare_Locks(xid);

	ResourceOwnerRelease(TopTransactionResourceOwner,
						 RESOURCE_RELEASE_LOCKS,
						 true, true);
	ResourceOwnerRelease(TopTransactionResourceOwner,
						 RESOURCE_RELEASE_AFTER_LOCKS,
						 true, true);

	/* Check we've released all catcache entries */
	AtEOXact_CatCache(true);

	/* PREPARE acts the same as COMMIT as far as GUC is concerned */
	AtEOXact_GUC(true, 1);
	AtEOXact_SPI(true);
	AtEOXact_xml();
	AtEOXact_on_commit_actions(true);
	AtEOXact_Namespace(true);
	/* smgrcommit already done */
	AtEOXact_Files();
	AtEOXact_ComboCid();
	AtEOXact_HashTables(true);
	/* don't call AtEOXact_PgStat here */

	CurrentResourceOwner = NULL;
	ResourceOwnerDelete(TopTransactionResourceOwner);
	s->curTransactionOwner = NULL;
	CurTransactionResourceOwner = NULL;
	TopTransactionResourceOwner = NULL;

	AtCommit_Memory();

	s->transactionId = InvalidTransactionId;
	s->subTransactionId = InvalidSubTransactionId;
	s->nestingLevel = 0;
	s->gucNestLevel = 0;
	s->childXids = NULL;
	s->nChildXids = 0;
	s->maxChildXids = 0;

	/*
	 * done with 1st phase commit processing, set current transaction state
	 * back to default
	 */
	s->state = TRANS_DEFAULT;

	RESUME_INTERRUPTS();
}


/*
 *	AbortTransaction
 */
static void
AbortTransaction(void)
{
	TransactionState s = CurrentTransactionState;
	TransactionId latestXid;

	/* Prevent cancel/die interrupt while cleaning up */
	HOLD_INTERRUPTS();

	/* Make sure we have a valid memory context and resource owner */
	AtAbort_Memory();
	AtAbort_ResourceOwner();

	/*
	 * Release any LW locks we might be holding as quickly as possible.
	 * (Regular locks, however, must be held till we finish aborting.)
	 * Releasing LW locks is critical since we might try to grab them again
	 * while cleaning up!
	 */
	LWLockReleaseAll();

	/* Clean up buffer I/O and buffer context locks, too */
	AbortBufferIO();
	UnlockBuffers();

	/*
	 * Also clean up any open wait for lock, since the lock manager will choke
	 * if we try to wait for another lock before doing this.
	 */
	LockWaitCancel();

	/*
	 * check the current transaction state
	 */
	if (s->state != TRANS_INPROGRESS && s->state != TRANS_PREPARE)
		elog(WARNING, "AbortTransaction while in %s state",
			 TransStateAsString(s->state));
	Assert(s->parent == NULL);

	/*
	 * set the current transaction state information appropriately during the
	 * abort processing
	 */
	s->state = TRANS_ABORT;

	/*
	 * Reset user ID which might have been changed transiently.  We need this
	 * to clean up in case control escaped out of a SECURITY DEFINER function
	 * or other local change of CurrentUserId; therefore, the prior value
	 * of SecurityDefinerContext also needs to be restored.
	 *
	 * (Note: it is not necessary to restore session authorization or role
	 * settings here because those can only be changed via GUC, and GUC will
	 * take care of rolling them back if need be.)
	 */
	SetUserIdAndContext(s->prevUser, s->prevSecDefCxt);

	/*
	 * do abort processing
	 */
	AfterTriggerEndXact(false);
	AtAbort_Portals();
	AtEOXact_LargeObject(false);	/* 'false' means it's abort */
	AtAbort_Notify();
	AtEOXact_UpdateFlatFiles(false);

	/*
	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
	 * far as assigning an XID to advertise).
	 */
	latestXid = RecordTransactionAbort(false);

	PG_TRACE1(transaction__abort, MyProc->lxid);

	/*
	 * Let others know about no transaction in progress by me. Note that this
	 * must be done _before_ releasing locks we hold and _after_
	 * RecordTransactionAbort.
	 */
	ProcArrayEndTransaction(MyProc, latestXid);

	/*
	 * Post-abort cleanup.	See notes in CommitTransaction() concerning
	 * ordering.
	 */

	CallXactCallbacks(XACT_EVENT_ABORT);

	ResourceOwnerRelease(TopTransactionResourceOwner,
						 RESOURCE_RELEASE_BEFORE_LOCKS,
						 false, true);
	AtEOXact_Buffers(false);
	AtEOXact_RelationCache(false);
	AtEOXact_Inval(false);
	smgrDoPendingDeletes(false);
	AtEOXact_MultiXact();
	ResourceOwnerRelease(TopTransactionResourceOwner,
						 RESOURCE_RELEASE_LOCKS,
						 false, true);
	ResourceOwnerRelease(TopTransactionResourceOwner,
						 RESOURCE_RELEASE_AFTER_LOCKS,
						 false, true);
	AtEOXact_CatCache(false);

	AtEOXact_GUC(false, 1);
	AtEOXact_SPI(false);
	AtEOXact_xml();
	AtEOXact_on_commit_actions(false);
	AtEOXact_Namespace(false);
	smgrabort();
	AtEOXact_Files();
	AtEOXact_ComboCid();
	AtEOXact_HashTables(false);
	AtEOXact_PgStat(false);
	pgstat_report_xact_timestamp(0);

	/*
	 * State remains TRANS_ABORT until CleanupTransaction().
	 */
	RESUME_INTERRUPTS();
}

/*
 *	CleanupTransaction
 */
static void
CleanupTransaction(void)
{
	TransactionState s = CurrentTransactionState;

	/*
	 * State should still be TRANS_ABORT from AbortTransaction().
	 */
	if (s->state != TRANS_ABORT)
		elog(FATAL, "CleanupTransaction: unexpected state %s",
			 TransStateAsString(s->state));

	/*
	 * do abort cleanup processing
	 */
	AtCleanup_Portals();		/* now safe to release portal memory */

	CurrentResourceOwner = NULL;	/* and resource owner */
	if (TopTransactionResourceOwner)
		ResourceOwnerDelete(TopTransactionResourceOwner);
	s->curTransactionOwner = NULL;
	CurTransactionResourceOwner = NULL;
	TopTransactionResourceOwner = NULL;

	AtCleanup_Memory();			/* and transaction memory */

	s->transactionId = InvalidTransactionId;
	s->subTransactionId = InvalidSubTransactionId;
	s->nestingLevel = 0;
	s->gucNestLevel = 0;
	s->childXids = NULL;
	s->nChildXids = 0;
	s->maxChildXids = 0;

	/*
	 * done with abort processing, set current transaction state back to
	 * default
	 */
	s->state = TRANS_DEFAULT;
}

/*
 *	StartTransactionCommand
 */
void
StartTransactionCommand(void)
{
	TransactionState s = CurrentTransactionState;

	switch (s->blockState)
	{
			/*
			 * if we aren't in a transaction block, we just do our usual start
			 * transaction.
			 */
		case TBLOCK_DEFAULT:
			StartTransaction();
			s->blockState = TBLOCK_STARTED;
			break;

			/*
			 * We are somewhere in a transaction block or subtransaction and
			 * about to start a new command.  For now we do nothing, but
			 * someday we may do command-local resource initialization. (Note
			 * that any needed CommandCounterIncrement was done by the
			 * previous CommitTransactionCommand.)
			 */
		case TBLOCK_INPROGRESS:
		case TBLOCK_SUBINPROGRESS:
			break;

			/*
			 * Here we are in a failed transaction block (one of the commands
			 * caused an abort) so we do nothing but remain in the abort
			 * state.  Eventually we will get a ROLLBACK command which will
			 * get us out of this state.  (It is up to other code to ensure
			 * that no commands other than ROLLBACK will be processed in these
			 * states.)
			 */
		case TBLOCK_ABORT:
		case TBLOCK_SUBABORT:
			break;

			/* These cases are invalid. */
		case TBLOCK_STARTED:
		case TBLOCK_BEGIN:
		case TBLOCK_SUBBEGIN:
		case TBLOCK_END:
		case TBLOCK_SUBEND:
		case TBLOCK_ABORT_END:
		case TBLOCK_SUBABORT_END:
		case TBLOCK_ABORT_PENDING:
		case TBLOCK_SUBABORT_PENDING:
		case TBLOCK_SUBRESTART:
		case TBLOCK_SUBABORT_RESTART:
		case TBLOCK_PREPARE:
			elog(ERROR, "StartTransactionCommand: unexpected state %s",
				 BlockStateAsString(s->blockState));
			break;
	}

	/*
	 * We must switch to CurTransactionContext before returning. This is
	 * already done if we called StartTransaction, otherwise not.
	 */
	Assert(CurTransactionContext != NULL);
	MemoryContextSwitchTo(CurTransactionContext);
}

/*
 *	CommitTransactionCommand
 */
void
CommitTransactionCommand(void)
{
	TransactionState s = CurrentTransactionState;

	switch (s->blockState)
	{
			/*
			 * This shouldn't happen, because it means the previous
			 * StartTransactionCommand didn't set the STARTED state
			 * appropriately.
			 */
		case TBLOCK_DEFAULT:
			elog(FATAL, "CommitTransactionCommand: unexpected state %s",
				 BlockStateAsString(s->blockState));
			break;

			/*
			 * If we aren't in a transaction block, just do our usual
			 * transaction commit, and return to the idle state.
			 */
		case TBLOCK_STARTED:
			CommitTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * We are completing a "BEGIN TRANSACTION" command, so we change
			 * to the "transaction block in progress" state and return.  (We
			 * assume the BEGIN did nothing to the database, so we need no
			 * CommandCounterIncrement.)
			 */
		case TBLOCK_BEGIN:
			s->blockState = TBLOCK_INPROGRESS;
			break;

			/*
			 * This is the case when we have finished executing a command
			 * someplace within a transaction block.  We increment the command
			 * counter and return.
			 */
		case TBLOCK_INPROGRESS:
		case TBLOCK_SUBINPROGRESS:
			CommandCounterIncrement();
			break;

			/*
			 * We are completing a "COMMIT" command.  Do it and return to the
			 * idle state.
			 */
		case TBLOCK_END:
			CommitTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * Here we are in the middle of a transaction block but one of the
			 * commands caused an abort so we do nothing but remain in the
			 * abort state.  Eventually we will get a ROLLBACK comand.
			 */
		case TBLOCK_ABORT:
		case TBLOCK_SUBABORT:
			break;

			/*
			 * Here we were in an aborted transaction block and we just got
			 * the ROLLBACK command from the user, so clean up the
			 * already-aborted transaction and return to the idle state.
			 */
		case TBLOCK_ABORT_END:
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * Here we were in a perfectly good transaction block but the user
			 * told us to ROLLBACK anyway.	We have to abort the transaction
			 * and then clean up.
			 */
		case TBLOCK_ABORT_PENDING:
			AbortTransaction();
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * We are completing a "PREPARE TRANSACTION" command.  Do it and
			 * return to the idle state.
			 */
		case TBLOCK_PREPARE:
			PrepareTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * We were just issued a SAVEPOINT inside a transaction b