Beispiel #1
0
/*
 * LockGXact
 *		Locate the prepared transaction and mark it busy for COMMIT or PREPARE.
 */
static GlobalTransaction
LockGXact(const char *gid, Oid user)
{
	int			i;

	LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);

	for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
	{
		GlobalTransaction gxact = TwoPhaseState->prepXacts[i];

		/* Ignore not-yet-valid GIDs */
		if (!gxact->valid)
			continue;
		if (strcmp(gxact->gid, gid) != 0)
			continue;

		/* Found it, but has someone else got it locked? */
		if (TransactionIdIsValid(gxact->locking_xid))
		{
			if (TransactionIdIsActive(gxact->locking_xid))
				ereport(ERROR,
						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				errmsg("prepared transaction with identifier \"%s\" is busy",
					   gid)));
			gxact->locking_xid = InvalidTransactionId;
		}

		if (user != gxact->owner && !superuser_arg(user))
			ereport(ERROR,
					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				  errmsg("permission denied to finish prepared transaction"),
					 errhint("Must be superuser or the user that prepared the transaction.")));

		/* OK for me to lock it */
		gxact->locking_xid = GetTopTransactionId();

		LWLockRelease(TwoPhaseStateLock);

		return gxact;
	}

	LWLockRelease(TwoPhaseStateLock);

	ereport(ERROR,
			(errcode(ERRCODE_UNDEFINED_OBJECT),
		 errmsg("prepared transaction with identifier \"%s\" does not exist",
				gid)));

	/* NOTREACHED */
	return NULL;
}
Beispiel #2
0
/*
 * LockGXact
 *		Locate the prepared transaction and mark it busy for COMMIT or PREPARE.
 */
static GlobalTransaction
LockGXact(const char *gid, Oid user)
{
	int			i;

	LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);

	for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
	{
		GlobalTransaction gxact = TwoPhaseState->prepXacts[i];

		/* Ignore not-yet-valid GIDs */
		if (!gxact->valid)
			continue;
		if (strcmp(gxact->gid, gid) != 0)
			continue;

		/* Found it, but has someone else got it locked? */
		if (TransactionIdIsValid(gxact->locking_xid))
		{
			if (TransactionIdIsActive(gxact->locking_xid))
				ereport(ERROR,
						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				errmsg("prepared transaction with identifier \"%s\" is busy",
					   gid)));
			gxact->locking_xid = InvalidTransactionId;
		}

		if (user != gxact->owner && !superuser_arg(user))
			ereport(ERROR,
					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				  errmsg("permission denied to finish prepared transaction"),
					 errhint("Must be superuser or the user that prepared the transaction.")));

		/*
		 * Note: it probably would be possible to allow committing from
		 * another database; but at the moment NOTIFY is known not to work and
		 * there may be some other issues as well.	Hence disallow until
		 * someone gets motivated to make it work.
		 */
		if (MyDatabaseId != gxact->proc.databaseId)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				  errmsg("prepared transaction belongs to another database"),
					 errhint("Connect to the database where the transaction was prepared to finish it.")));

		/* OK for me to lock it */
		gxact->locking_xid = GetTopTransactionId();

		LWLockRelease(TwoPhaseStateLock);

		return gxact;
	}

	LWLockRelease(TwoPhaseStateLock);

	ereport(ERROR,
			(errcode(ERRCODE_UNDEFINED_OBJECT),
		 errmsg("prepared transaction with identifier \"%s\" does not exist",
				gid)));

	/* NOTREACHED */
	return NULL;
}
Beispiel #3
0
/*
 * MarkAsPreparing
 *		Reserve the GID for the given transaction.
 *
 * Internally, this creates a gxact struct and puts it into the active array.
 * NOTE: this is also used when reloading a gxact after a crash; so avoid
 * assuming that we can use very much backend context.
 */
GlobalTransaction
MarkAsPreparing(TransactionId xid, const char *gid,
				TimestampTz prepared_at, Oid owner, Oid databaseid)
{
	GlobalTransaction gxact;
	int			i;

	if (strlen(gid) >= GIDSIZE)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("transaction identifier \"%s\" is too long",
						gid)));

	/* fail immediately if feature is disabled */
	if (max_prepared_xacts == 0)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("prepared transactions are disabled"),
			  errhint("Set max_prepared_transactions to a nonzero value.")));

	LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);

	/*
	 * First, find and recycle any gxacts that failed during prepare. We do
	 * this partly to ensure we don't mistakenly say their GIDs are still
	 * reserved, and partly so we don't fail on out-of-slots unnecessarily.
	 */
	for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
	{
		gxact = TwoPhaseState->prepXacts[i];
		if (!gxact->valid && !TransactionIdIsActive(gxact->locking_xid))
		{
			/* It's dead Jim ... remove from the active array */
			TwoPhaseState->numPrepXacts--;
			TwoPhaseState->prepXacts[i] = TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
			/* and put it back in the freelist */
			gxact->proc.links.next = (SHM_QUEUE *) TwoPhaseState->freeGXacts;
			TwoPhaseState->freeGXacts = gxact;
			/* Back up index count too, so we don't miss scanning one */
			i--;
		}
	}

	/* Check for conflicting GID */
	for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
	{
		gxact = TwoPhaseState->prepXacts[i];
		if (strcmp(gxact->gid, gid) == 0)
		{
			ereport(ERROR,
					(errcode(ERRCODE_DUPLICATE_OBJECT),
					 errmsg("transaction identifier \"%s\" is already in use",
							gid)));
		}
	}

	/* Get a free gxact from the freelist */
	if (TwoPhaseState->freeGXacts == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_OUT_OF_MEMORY),
				 errmsg("maximum number of prepared transactions reached"),
				 errhint("Increase max_prepared_transactions (currently %d).",
						 max_prepared_xacts)));
	gxact = TwoPhaseState->freeGXacts;
	TwoPhaseState->freeGXacts = (GlobalTransaction) gxact->proc.links.next;

	/* Initialize it */
	MemSet(&gxact->proc, 0, sizeof(PGPROC));
	SHMQueueElemInit(&(gxact->proc.links));
	gxact->proc.waitStatus = STATUS_OK;
	/* We set up the gxact's VXID as InvalidBackendId/XID */
	gxact->proc.lxid = (LocalTransactionId) xid;
	gxact->proc.xid = xid;
	gxact->proc.xmin = InvalidTransactionId;
	gxact->proc.pid = 0;
	gxact->proc.backendId = InvalidBackendId;
	gxact->proc.databaseId = databaseid;
	gxact->proc.roleId = owner;
	gxact->proc.inCommit = false;
	gxact->proc.vacuumFlags = 0;
	gxact->proc.lwWaiting = false;
	gxact->proc.lwExclusive = false;
	gxact->proc.lwWaitLink = NULL;
	gxact->proc.waitLock = NULL;
	gxact->proc.waitProcLock = NULL;
	for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
		SHMQueueInit(&(gxact->proc.myProcLocks[i]));
	/* subxid data must be filled later by GXactLoadSubxactData */
	gxact->proc.subxids.overflowed = false;
	gxact->proc.subxids.nxids = 0;

	gxact->prepared_at = prepared_at;
	/* initialize LSN to 0 (start of WAL) */
	gxact->prepare_lsn.xlogid = 0;
	gxact->prepare_lsn.xrecoff = 0;
	gxact->owner = owner;
	gxact->locking_xid = xid;
	gxact->valid = false;
	strcpy(gxact->gid, gid);

	/* And insert it into the active array */
	Assert(TwoPhaseState->numPrepXacts < max_prepared_xacts);
	TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts++] = gxact;

	LWLockRelease(TwoPhaseStateLock);

	return gxact;
}