xact.c

PostgreSQL7.4.6 for Linux

	s->state = TRANS_COMMIT;

	/*
	 * Do pre-commit processing (most of this stuff requires database
	 * access, and in fact could still cause an error...)
	 */

	AtCommit_Portals();

	/* handle commit for large objects [ PA, 7/17/98 ] */
	/* XXX probably this does not belong here */
	lo_commit(true);

	/* NOTIFY commit must come before lower-level cleanup */
	AtCommit_Notify();

	/* Update the flat password file if we changed pg_shadow or pg_group */
	AtEOXact_UpdatePasswordFile(true);

	/*
	 * Here is where we really truly commit.
	 */
	RecordTransactionCommit();

	/*
	 * Let others know about no transaction in progress by me. Note that
	 * this must be done _before_ releasing locks we hold and _after_
	 * RecordTransactionCommit.
	 *
	 * LWLockAcquire(SInvalLock) is required: UPDATE with xid 0 is blocked by
	 * xid 1' UPDATE, xid 1 is doing commit while xid 2 gets snapshot - if
	 * xid 2' GetSnapshotData sees xid 1 as running then it must see xid 0
	 * as running as well or it will see two tuple versions - one deleted
	 * by xid 1 and one inserted by xid 0.	See notes in GetSnapshotData.
	 */
	if (MyProc != (PGPROC *) NULL)
	{
		/* Lock SInvalLock because that's what GetSnapshotData uses. */
		LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
		MyProc->xid = InvalidTransactionId;
		MyProc->xmin = InvalidTransactionId;
		LWLockRelease(SInvalLock);
	}

	/*
	 * This is all post-commit cleanup.  Note that if an error is raised
	 * here, it's too late to abort the transaction.  This should be just
	 * noncritical resource releasing.
	 *
	 * The ordering of operations is not entirely random.  The idea is:
	 * release resources visible to other backends (eg, files, buffer
	 * pins); then release locks; then release backend-local resources. We
	 * want to release locks at the point where any backend waiting for us
	 * will see our transaction as being fully cleaned up.
	 */

	smgrDoPendingDeletes(true);
	AtCommit_Cache();
	AtEOXact_Buffers(true);
	/* smgrcommit already done */

	AtCommit_Locks();

	CallEOXactCallbacks(true);
	AtEOXact_GUC(true);
	AtEOXact_SPI();
	AtEOXact_gist();
	AtEOXact_hash();
	AtEOXact_nbtree();
	AtEOXact_rtree();
	AtEOXact_on_commit_actions(true);
	AtEOXact_Namespace(true);
	AtEOXact_CatCache(true);
	AtEOXact_Files();
	pgstat_count_xact_commit();
	AtCommit_Memory();

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

	RESUME_INTERRUPTS();
}

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

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

	/*
	 * 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)
		elog(WARNING, "AbortTransaction and not in in-progress state");

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

	/* Make sure we are in a valid memory context */
	AtAbort_Memory();

	/*
	 * Reset user id which might have been changed transiently
	 */
	SetUserId(GetSessionUserId());

	/*
	 * do abort processing
	 */
	DeferredTriggerAbortXact();
	AtAbort_Portals();
	lo_commit(false);			/* 'false' means it's abort */
	AtAbort_Notify();
	AtEOXact_UpdatePasswordFile(false);

	/* Advertise the fact that we aborted in pg_clog. */
	RecordTransactionAbort();

	/*
	 * Let others know about no transaction in progress by me. Note that
	 * this must be done _before_ releasing locks we hold and _after_
	 * RecordTransactionAbort.
	 */
	if (MyProc != (PGPROC *) NULL)
	{
		/* Lock SInvalLock because that's what GetSnapshotData uses. */
		LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
		MyProc->xid = InvalidTransactionId;
		MyProc->xmin = InvalidTransactionId;
		LWLockRelease(SInvalLock);
	}

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

	smgrDoPendingDeletes(false);
	AtAbort_Cache();
	AtEOXact_Buffers(false);
	smgrabort();

	AtAbort_Locks();

	CallEOXactCallbacks(false);
	AtEOXact_GUC(false);
	AtEOXact_SPI();
	AtEOXact_gist();
	AtEOXact_hash();
	AtEOXact_nbtree();
	AtEOXact_rtree();
	AtEOXact_on_commit_actions(false);
	AtEOXact_Namespace(false);
	AtEOXact_CatCache(false);
	AtEOXact_Files();
	SetReindexProcessing(InvalidOid, InvalidOid);
	pgstat_count_xact_rollback();

	/*
	 * 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 and not in abort state");

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

	/*
	 * 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();
			break;

			/*
			 * We should never experience this -- if we do it means the
			 * BEGIN state was not changed in the previous
			 * CommitTransactionCommand().	If we get it, we print a
			 * warning and change to the in-progress state.
			 */
		case TBLOCK_BEGIN:
			elog(WARNING, "StartTransactionCommand: unexpected TBLOCK_BEGIN");
			s->blockState = TBLOCK_INPROGRESS;
			break;

			/*
			 * This is the case when are somewhere in a transaction block
			 * and about to start a new command.  For now we do nothing
			 * but someday we may do command-local resource
			 * initialization.
			 */
		case TBLOCK_INPROGRESS:
			break;

			/*
			 * As with BEGIN, we should never experience this if we do it
			 * means the END state was not changed in the previous
			 * CommitTransactionCommand().	If we get it, we print a
			 * warning, commit the transaction, start a new transaction
			 * and change to the default state.
			 */
		case TBLOCK_END:
			elog(WARNING, "StartTransactionCommand: unexpected TBLOCK_END");
			s->blockState = TBLOCK_DEFAULT;
			CommitTransaction();
			StartTransaction();
			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 to the "END
			 * TRANSACTION" which will set things straight.
			 */
		case TBLOCK_ABORT:
			break;

			/*
			 * This means we somehow aborted and the last call to
			 * CommitTransactionCommand() didn't clear the state so we
			 * remain in the ENDABORT state and maybe next time we get to
			 * CommitTransactionCommand() the state will get reset to
			 * default.
			 */
		case TBLOCK_ENDABORT:
			elog(WARNING, "StartTransactionCommand: unexpected TBLOCK_ENDABORT");
			break;
	}

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

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

	switch (s->blockState)
	{
			/*
			 * If we aren't in a transaction block, just do our usual
			 * transaction commit.
			 */
		case TBLOCK_DEFAULT:
			CommitTransaction();
			break;

			/*
			 * This is the case right after we get a "BEGIN TRANSACTION"
			 * command, but the user hasn't done anything else yet, so we
			 * change to the "transaction block in progress" state and
			 * return.
			 */
		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:
			CommandCounterIncrement();
			break;

			/*
			 * This is the case when we just got the "END TRANSACTION"
			 * statement, so we commit the transaction and go back to the
			 * default 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 to the "END
			 * TRANSACTION" which will set things straight.
			 */
		case TBLOCK_ABORT:
			break;

			/*
			 * Here we were in an aborted transaction block which just
			 * processed the "END TRANSACTION" command from the user, so
			 * clean up and return to the default state.
			 */
		case TBLOCK_ENDABORT:
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;
	}
}

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

	switch (s->blockState)
	{
			/*
			 * if we aren't in a transaction block, we just do the basic
			 * abort & cleanup transaction.
			 */
		case TBLOCK_DEFAULT:
			AbortTransaction();
			CleanupTransaction();
			break;

			/*
			 * If we are in the TBLOCK_BEGIN it means something screwed up
			 * right after reading "BEGIN TRANSACTION" so we enter the
			 * abort state.  Eventually an "END TRANSACTION" will fix
			 * things.
			 */
		case TBLOCK_BEGIN:
			s->blockState = TBLOCK_ABORT;
			AbortTransaction();
			/* CleanupTransaction happens when we exit TBLOCK_ABORT */
			break;

			/*
			 * This is the case when are somewhere in a transaction block
			 * which aborted so we abort the transaction and set the ABORT
			 * state.  Eventually an "END TRANSACTION" will fix things and
			 * restore us to a normal state.
			 */
		case TBLOCK_INPROGRESS:
			s->blockState = TBLOCK_ABORT;
			AbortTransaction();
			/* CleanupTransaction happens when we exit TBLOCK_ABORT */
			break;

			/*
			 * Here, the system was fouled up just after the user wanted
			 * to end the transaction block so we abort the transaction
			 * and put us back into the default state.
			 */
		case TBLOCK_END:
			s->blockState = TBLOCK_DEFAULT;
			AbortTransaction();
			CleanupTransaction();
			break;

			/*
			 * Here, we are already in an aborted transaction state and
			 * are waiting for an "END TRANSACTION" to come along and lo
			 * and behold, we abort again! So we just remain in the abort
			 * state.
			 */
		case TBLOCK_ABORT:
			break;

			/*
			 * Here we were in an aborted transaction block which just
			 * processed the "END TRANSACTION" command but somehow aborted
			 * again.. since we must have done the abort processing, we
			 * clean up and return to the default state.
			 */
		case TBLOCK_ENDABORT:
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;
	}
}

/*
 *	PreventTransactionChain
 *
 *	This routine is to be called by statements that must not run inside
 *	a transaction block, typically because they have non-rollback-able
 *	side effects or do internal commits.
 *
 *	If we have already started a transaction block, issue an error; also issue
 *	an error if we appear to be running inside a user-defined function (which
 *	could issue more commands and possibly cause a failure after the statement
 *	completes).
 *
 *	stmtNode: pointer to parameter block for statement; this is used in
 *	a very klugy way to determine whether we are inside a function.
 *	stmtType: statement type name for error messages.
 */
void
PreventTransactionChain(void *stmtNode, const char *stmtType)
{
	/*
	 * xact block already started?
	 */
	if (IsTransactionBlock())
		ereport(ERROR,