xact.c

来自「PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统」· C语言 代码 · 共 2,442 行 · 第 1/5 页

	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->childXids = NIL;

	/*
	 * 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 block.
			 * Start a subtransaction.	(DefineSavepoint already did
			 * PushTransaction, so as to have someplace to put the SUBBEGIN
			 * state.)
			 */
		case TBLOCK_SUBBEGIN:
			StartSubTransaction();
			s->blockState = TBLOCK_SUBINPROGRESS;
			break;

			/*
			 * We were issued a COMMIT or RELEASE command, so we end the
			 * current subtransaction and return to the parent transaction.
			 * The parent might be ended too, so repeat till we are all the
			 * way out or find an INPROGRESS transaction.
			 */
		case TBLOCK_SUBEND:
			do
			{
				CommitSubTransaction();
				s = CurrentTransactionState;	/* changed by pop */
			} while (s->blockState == TBLOCK_SUBEND);
			/* If we had a COMMIT command, finish off the main xact too */
			if (s->blockState == TBLOCK_END)
			{
				Assert(s->parent == NULL);
				CommitTransaction();
				s->blockState = TBLOCK_DEFAULT;
			}
			else if (s->blockState == TBLOCK_PREPARE)
			{
				Assert(s->parent == NULL);
				PrepareTransaction();
				s->blockState = TBLOCK_DEFAULT;
			}
			else
			{
				Assert(s->blockState == TBLOCK_INPROGRESS ||
					   s->blockState == TBLOCK_SUBINPROGRESS);
			}
			break;

			/*
			 * The current already-failed subtransaction is ending due to a
			 * ROLLBACK or ROLLBACK TO command, so pop it and recursively
			 * examine the parent (which could be in any of several states).
			 */
		case TBLOCK_SUBABORT_END:
			CleanupSubTransaction();
			CommitTransactionCommand();
			break;

			/*
			 * As above, but it's not dead yet, so abort first.
			 */
		case TBLOCK_SUBABORT_PENDING:
			AbortSubTransaction();
			CleanupSubTransaction();
			CommitTransactionCommand();
			break;

			/*
			 * The current subtransaction is the target of a ROLLBACK TO
			 * command.  Abort and pop it, then start a new subtransaction
			 * with the same name.
			 */
		case TBLOCK_SUBRESTART:
			{
				char	   *name;
				int			savepointLevel;

				/* save name and keep Cleanup from freeing it */
				name = s->name;
				s->name = NULL;
				savepointLevel = s->savepointLevel;

				AbortSubTransaction();
				CleanupSubTransaction();

				DefineSavepoint(NULL);
				s = CurrentTransactionState;	/* changed by push */
				s->name = name;
				s->savepointLevel = savepointLevel;

				/* This is the same as TBLOCK_SUBBEGIN case */
				AssertState(s->blockState == TBLOCK_SUBBEGIN);
				StartSubTransaction();
				s->blockState = TBLOCK_SUBINPROGRESS;
			}
			break;

			/*
			 * Same as above, but the subtransaction had already failed, so we
			 * don't need AbortSubTransaction.
			 */
		case TBLOCK_SUBABORT_RESTART:
			{
				char	   *name;
				int			savepointLevel;

				/* save name and keep Cleanup from freeing it */
				name = s->name;
				s->name = NULL;
				savepointLevel = s->savepointLevel;

				CleanupSubTransaction();

				DefineSavepoint(NULL);
				s = CurrentTransactionState;	/* changed by push */
				s->name = name;
				s->savepointLevel = savepointLevel;

				/* This is the same as TBLOCK_SUBBEGIN case */
				AssertState(s->blockState == TBLOCK_SUBBEGIN);
				StartSubTransaction();
				s->blockState = TBLOCK_SUBINPROGRESS;
			}
			break;
	}
}

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

	switch (s->blockState)
	{
		case TBLOCK_DEFAULT:
			if (s->state == TRANS_DEFAULT)
			{
				/* we are idle, so nothing to do */
			}
			else
			{
				/*
				 * We can get here after an error during transaction start
				 * (state will be TRANS_START).  Need to clean up the
				 * incompletely started transaction.  First, adjust the
				 * low-level state to suppress warning message from
				 * AbortTransaction.
				 */
				if (s->state == TRANS_START)
					s->state = TRANS_INPROGRESS;
				AbortTransaction();
				CleanupTransaction();
			}
			break;

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

			/*
			 * If we are in TBLOCK_BEGIN it means something screwed up right
			 * after reading "BEGIN TRANSACTION".  We assume that the user
			 * will interpret the error as meaning the BEGIN failed to get him
			 * into a transaction block, so we should abort and return to idle
			 * state.
			 */
		case TBLOCK_BEGIN:
			AbortTransaction();
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * We are somewhere in a transaction block and we've gotten a
			 * failure, so we abort the transaction and set up the persistent
			 * ABORT state.  We will stay in ABORT until we get a ROLLBACK.
			 */
		case TBLOCK_INPROGRESS:
			AbortTransaction();
			s->blockState = TBLOCK_ABORT;
			/* CleanupTransaction happens when we exit TBLOCK_ABORT_END */
			break;

			/*
			 * Here, we failed while trying to COMMIT.	Clean up the
			 * transaction and return to idle state (we do not want to stay in
			 * the transaction).
			 */
		case TBLOCK_END:
			AbortTransaction();
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * Here, we are already in an aborted transaction state and are
			 * waiting for a ROLLBACK, but for some reason we failed again! So
			 * we just remain in the abort state.
			 */
		case TBLOCK_ABORT:
		case TBLOCK_SUBABORT:
			break;

			/*
			 * We are in a failed transaction and we got the ROLLBACK command.
			 * We have already aborted, we just need to cleanup and go to idle
			 * state.
			 */
		case TBLOCK_ABORT_END:
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * We are in a live transaction and we got a ROLLBACK command.
			 * Abort, cleanup, go to idle state.
			 */
		case TBLOCK_ABORT_PENDING:
			AbortTransaction();
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * Here, we failed while trying to PREPARE.  Clean up the
			 * transaction and return to idle state (we do not want to stay in
			 * the transaction).
			 */
		case TBLOCK_PREPARE:
			AbortTransaction();
			CleanupTransaction();
			s->blockState = TBLOCK_DEFAULT;
			break;

			/*
			 * We got an error inside a subtransaction.  Abort just the
			 * subtransaction, and go to the persistent SUBABORT state until
			 * we get ROLLBACK.
			 */
		case TBLOCK_SUBINPROGRESS:
			AbortSubTransaction();
			s->blockState = TBLOCK_SUBABORT;
			break;

			/*
			 * If we failed while trying to create a subtransaction, clean up
			 * the broken subtransaction and abort the parent.	The same
			 * applies if we get a failure while ending a subtransaction.
			 */
		case TBLOCK_SUBBEGIN:
		case TBLOCK_SUBEND:
		case TBLOCK_SUBABORT_PENDING:
		case TBLOCK_SUBRESTART:
			AbortSubTransaction();
			CleanupSubTransaction();
			AbortCurrentTransaction();
			break;

			/*
			 * Same as above, except the Abort() was already done.
			 */
		case TBLOCK_SUBABORT_END:
		case TBLOCK_SUBABORT_RESTART:
			CleanupSubTransaction();
			AbortCurrentTransaction();
			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).  Subtransactions are verboten too.
 *
 *	stmtN