Beispiel #1
0
/*
 * HeapTupleSatisfiesToast
 *		True iff heap tuple is valid as a TOAST row.
 *
 * This is a simplified version that only checks for VACUUM moving conditions.
 * It's appropriate for TOAST usage because TOAST really doesn't want to do
 * its own time qual checks; if you can see the main table row that contains
 * a TOAST reference, you should be able to see the TOASTed value.  However,
 * vacuuming a TOAST table is independent of the main table, and in case such
 * a vacuum fails partway through, we'd better do this much checking.
 *
 * Among other things, this means you can't do UPDATEs of rows in a TOAST
 * table.
 */
bool
HeapTupleSatisfiesToast(HeapTuple htup, Snapshot snapshot,
						Buffer buffer)
{
	HeapTupleHeader tuple = htup->t_data;

	Assert(ItemPointerIsValid(&htup->t_self));
	Assert(htup->t_tableOid != InvalidOid);

	if (!HeapTupleHeaderXminCommitted(tuple))
	{
		if (HeapTupleHeaderXminInvalid(tuple))
			return false;

		/* Used by pre-9.0 binary upgrades */
		if (tuple->t_infomask & HEAP_MOVED_OFF)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (TransactionIdIsCurrentTransactionId(xvac))
				return false;
			if (!TransactionIdIsInProgress(xvac))
			{
				if (TransactionIdDidCommit(xvac))
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return false;
				}
				SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
							InvalidTransactionId);
			}
		}
		/* Used by pre-9.0 binary upgrades */
		else if (tuple->t_infomask & HEAP_MOVED_IN)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (!TransactionIdIsCurrentTransactionId(xvac))
			{
				if (TransactionIdIsInProgress(xvac))
					return false;
				if (TransactionIdDidCommit(xvac))
					SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
								InvalidTransactionId);
				else
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return false;
				}
			}
		}
	}

	/* otherwise assume the tuple is valid for TOAST. */
	return true;
}
Beispiel #2
0
/*
 * HeapTupleIsSurelyDead
 *
 *	Determine whether a tuple is surely dead.  We sometimes use this
 *	in lieu of HeapTupleSatisifesVacuum when the tuple has just been
 *	tested by HeapTupleSatisfiesMVCC and, therefore, any hint bits that
 *	can be set should already be set.  We assume that if no hint bits
 *	either for xmin or xmax, the transaction is still running.  This is
 *	therefore faster than HeapTupleSatisfiesVacuum, because we don't
 *	consult CLOG (and also because we don't need to give an exact answer,
 *	just whether or not the tuple is surely dead).
 */
bool
HeapTupleIsSurelyDead(HeapTuple htup, TransactionId OldestXmin)
{
	HeapTupleHeader tuple = htup->t_data;

	Assert(ItemPointerIsValid(&htup->t_self));
	Assert(htup->t_tableOid != InvalidOid);

	/*
	 * If the inserting transaction is marked invalid, then it aborted, and
	 * the tuple is definitely dead.  If it's marked neither committed nor
	 * invalid, then we assume it's still alive (since the presumption is that
	 * all relevant hint bits were just set moments ago).
	 */
	if (!HeapTupleHeaderXminCommitted(tuple))
		return HeapTupleHeaderXminInvalid(tuple) ? true : false;

	/*
	 * If the inserting transaction committed, but any deleting transaction
	 * aborted, the tuple is still alive.
	 */
	if (tuple->t_infomask & HEAP_XMAX_INVALID)
		return false;

	/*
	 * If the XMAX is just a lock, the tuple is still alive.
	 */
	if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
		return false;

	/*
	 * If the Xmax is a MultiXact, it might be dead or alive, but we cannot
	 * know without checking pg_multixact.
	 */
	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
		return false;

	/* If deleter isn't known to have committed, assume it's still running. */
	if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
		return false;

	/* Deleter committed, so tuple is dead if the XID is old enough. */
	return TransactionIdPrecedes(HeapTupleHeaderGetRawXmax(tuple), OldestXmin);
}
Beispiel #3
0
/*
 * Given a tuple we are about to delete, determine the correct value to store
 * into its t_cid field.
 *
 * If we don't need a combo CID, *cmax is unchanged and *iscombo is set to
 * FALSE.  If we do need one, *cmax is replaced by a combo CID and *iscombo
 * is set to TRUE.
 *
 * The reason this is separate from the actual HeapTupleHeaderSetCmax()
 * operation is that this could fail due to out-of-memory conditions.  Hence
 * we need to do this before entering the critical section that actually
 * changes the tuple in shared buffers.
 */
void
HeapTupleHeaderAdjustCmax(HeapTupleHeader tup,
						  CommandId *cmax,
						  bool *iscombo)
{
	/*
	 * If we're marking a tuple deleted that was inserted by (any
	 * subtransaction of) our transaction, we need to use a combo command id.
	 * Test for HeapTupleHeaderXminCommitted() first, because it's cheaper than a
	 * TransactionIdIsCurrentTransactionId call.
	 */
	if (!HeapTupleHeaderXminCommitted(tup) &&
		TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tup)))
	{
		CommandId	cmin = HeapTupleHeaderGetCmin(tup);

		*cmax = GetComboCommandId(cmin, *cmax);
		*iscombo = true;
	}
	else
	{
		*iscombo = false;
	}
}
Beispiel #4
0
/*
 * HeapTupleSatisfiesMVCC
 *		True iff heap tuple is valid for the given MVCC snapshot.
 *
 *	Here, we consider the effects of:
 *		all transactions committed as of the time of the given snapshot
 *		previous commands of this transaction
 *
 *	Does _not_ include:
 *		transactions shown as in-progress by the snapshot
 *		transactions started after the snapshot was taken
 *		changes made by the current command
 *
 * (Notice, however, that the tuple status hint bits will be updated on the
 * basis of the true state of the transaction, even if we then pretend we
 * can't see it.)
 */
bool
HeapTupleSatisfiesMVCC(HeapTuple htup, Snapshot snapshot,
					   Buffer buffer)
{
	HeapTupleHeader tuple = htup->t_data;

	Assert(ItemPointerIsValid(&htup->t_self));
	Assert(htup->t_tableOid != InvalidOid);

	if (!HeapTupleHeaderXminCommitted(tuple))
	{
		if (HeapTupleHeaderXminInvalid(tuple))
			return false;

		/* Used by pre-9.0 binary upgrades */
		if (tuple->t_infomask & HEAP_MOVED_OFF)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (TransactionIdIsCurrentTransactionId(xvac))
				return false;
			if (!TransactionIdIsInProgress(xvac))
			{
				if (TransactionIdDidCommit(xvac))
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return false;
				}
				SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
							InvalidTransactionId);
			}
		}
		/* Used by pre-9.0 binary upgrades */
		else if (tuple->t_infomask & HEAP_MOVED_IN)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (!TransactionIdIsCurrentTransactionId(xvac))
			{
				if (TransactionIdIsInProgress(xvac))
					return false;
				if (TransactionIdDidCommit(xvac))
					SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
								InvalidTransactionId);
				else
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return false;
				}
			}
		}
		else if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tuple)))
		{
			if (HeapTupleHeaderGetCmin(tuple) >= snapshot->curcid)
				return false;	/* inserted after scan started */

			if (tuple->t_infomask & HEAP_XMAX_INVALID)	/* xid invalid */
				return true;

			if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))	/* not deleter */
				return true;

			if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
			{
				TransactionId xmax;

				xmax = HeapTupleGetUpdateXid(tuple);

				/* not LOCKED_ONLY, so it has to have an xmax */
				Assert(TransactionIdIsValid(xmax));

				/* updating subtransaction must have aborted */
				if (!TransactionIdIsCurrentTransactionId(xmax))
					return true;
				else if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
					return true;	/* updated after scan started */
				else
					return false;		/* updated before scan started */
			}

			if (!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
			{
				/* deleting subtransaction must have aborted */
				SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
							InvalidTransactionId);
				return true;
			}

			if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
				return true;	/* deleted after scan started */
			else
				return false;	/* deleted before scan started */
		}
		else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
			return false;
		else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
			SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
						HeapTupleHeaderGetRawXmin(tuple));
		else
		{
			/* it must have aborted or crashed */
			SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
						InvalidTransactionId);
			return false;
		}
	}

	/*
	 * By here, the inserting transaction has committed - have to check
	 * when...
	 */
	if (!HeapTupleHeaderXminFrozen(tuple)
		&& XidInMVCCSnapshot(HeapTupleHeaderGetRawXmin(tuple), snapshot))
		return false;			/* treat as still in progress */

	if (tuple->t_infomask & HEAP_XMAX_INVALID)	/* xid invalid or aborted */
		return true;

	if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
		return true;

	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
	{
		TransactionId xmax;

		/* already checked above */
		Assert(!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask));

		xmax = HeapTupleGetUpdateXid(tuple);

		/* not LOCKED_ONLY, so it has to have an xmax */
		Assert(TransactionIdIsValid(xmax));

		if (TransactionIdIsCurrentTransactionId(xmax))
		{
			if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
				return true;	/* deleted after scan started */
			else
				return false;	/* deleted before scan started */
		}
		if (TransactionIdIsInProgress(xmax))
			return true;
		if (TransactionIdDidCommit(xmax))
		{
			/* updating transaction committed, but when? */
			if (XidInMVCCSnapshot(xmax, snapshot))
				return true;	/* treat as still in progress */
			return false;
		}
		/* it must have aborted or crashed */
		return true;
	}

	if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
	{
		if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
		{
			if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
				return true;	/* deleted after scan started */
			else
				return false;	/* deleted before scan started */
		}

		if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
			return true;

		if (!TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
		{
			/* it must have aborted or crashed */
			SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
						InvalidTransactionId);
			return true;
		}

		/* xmax transaction committed */
		SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
					HeapTupleHeaderGetRawXmax(tuple));
	}

	/*
	 * OK, the deleting transaction committed too ... but when?
	 */
	if (XidInMVCCSnapshot(HeapTupleHeaderGetRawXmax(tuple), snapshot))
		return true;			/* treat as still in progress */

	return false;
}
Beispiel #5
0
/*
 * HeapTupleSatisfiesDirty
 *		True iff heap tuple is valid including effects of open transactions.
 *
 *	Here, we consider the effects of:
 *		all committed and in-progress transactions (as of the current instant)
 *		previous commands of this transaction
 *		changes made by the current command
 *
 * This is essentially like HeapTupleSatisfiesSelf as far as effects of
 * the current transaction and committed/aborted xacts are concerned.
 * However, we also include the effects of other xacts still in progress.
 *
 * A special hack is that the passed-in snapshot struct is used as an
 * output argument to return the xids of concurrent xacts that affected the
 * tuple.  snapshot->xmin is set to the tuple's xmin if that is another
 * transaction that's still in progress; or to InvalidTransactionId if the
 * tuple's xmin is committed good, committed dead, or my own xact.  Similarly
 * for snapshot->xmax and the tuple's xmax.
 */
bool
HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
						Buffer buffer)
{
	HeapTupleHeader tuple = htup->t_data;

	Assert(ItemPointerIsValid(&htup->t_self));
	Assert(htup->t_tableOid != InvalidOid);

	snapshot->xmin = snapshot->xmax = InvalidTransactionId;

	if (!HeapTupleHeaderXminCommitted(tuple))
	{
		if (HeapTupleHeaderXminInvalid(tuple))
			return false;

		/* Used by pre-9.0 binary upgrades */
		if (tuple->t_infomask & HEAP_MOVED_OFF)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (TransactionIdIsCurrentTransactionId(xvac))
				return false;
			if (!TransactionIdIsInProgress(xvac))
			{
				if (TransactionIdDidCommit(xvac))
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return false;
				}
				SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
							InvalidTransactionId);
			}
		}
		/* Used by pre-9.0 binary upgrades */
		else if (tuple->t_infomask & HEAP_MOVED_IN)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (!TransactionIdIsCurrentTransactionId(xvac))
			{
				if (TransactionIdIsInProgress(xvac))
					return false;
				if (TransactionIdDidCommit(xvac))
					SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
								InvalidTransactionId);
				else
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return false;
				}
			}
		}
		else if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tuple)))
		{
			if (tuple->t_infomask & HEAP_XMAX_INVALID)	/* xid invalid */
				return true;

			if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))	/* not deleter */
				return true;

			if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
			{
				TransactionId xmax;

				xmax = HeapTupleGetUpdateXid(tuple);

				/* not LOCKED_ONLY, so it has to have an xmax */
				Assert(TransactionIdIsValid(xmax));

				/* updating subtransaction must have aborted */
				if (!TransactionIdIsCurrentTransactionId(xmax))
					return true;
				else
					return false;
			}

			if (!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
			{
				/* deleting subtransaction must have aborted */
				SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
							InvalidTransactionId);
				return true;
			}

			return false;
		}
		else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
		{
			snapshot->xmin = HeapTupleHeaderGetRawXmin(tuple);
			/* XXX shouldn't we fall through to look at xmax? */
			return true;		/* in insertion by other */
		}
		else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
			SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
						HeapTupleHeaderGetRawXmin(tuple));
		else
		{
			/* it must have aborted or crashed */
			SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
						InvalidTransactionId);
			return false;
		}
	}

	/* by here, the inserting transaction has committed */

	if (tuple->t_infomask & HEAP_XMAX_INVALID)	/* xid invalid or aborted */
		return true;

	if (tuple->t_infomask & HEAP_XMAX_COMMITTED)
	{
		if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
			return true;
		return false;			/* updated by other */
	}

	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
	{
		TransactionId xmax;

		if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
			return true;

		xmax = HeapTupleGetUpdateXid(tuple);

		/* not LOCKED_ONLY, so it has to have an xmax */
		Assert(TransactionIdIsValid(xmax));

		if (TransactionIdIsCurrentTransactionId(xmax))
			return false;
		if (TransactionIdIsInProgress(xmax))
		{
			snapshot->xmax = xmax;
			return true;
		}
		if (TransactionIdDidCommit(xmax))
			return false;
		/* it must have aborted or crashed */
		return true;
	}

	if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
	{
		if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
			return true;
		return false;
	}

	if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
	{
		if (!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
			snapshot->xmax = HeapTupleHeaderGetRawXmax(tuple);
		return true;
	}

	if (!TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
	{
		/* it must have aborted or crashed */
		SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
					InvalidTransactionId);
		return true;
	}

	/* xmax transaction committed */

	if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
	{
		SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
					InvalidTransactionId);
		return true;
	}

	SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
				HeapTupleHeaderGetRawXmax(tuple));
	return false;				/* updated by other */
}
Beispiel #6
0
/*
 * HeapTupleSatisfiesUpdate
 *
 *	This function returns a more detailed result code than most of the
 *	functions in this file, since UPDATE needs to know more than "is it
 *	visible?".  It also allows for user-supplied CommandId rather than
 *	relying on CurrentCommandId.
 *
 *	The possible return codes are:
 *
 *	HeapTupleInvisible: the tuple didn't exist at all when the scan started,
 *	e.g. it was created by a later CommandId.
 *
 *	HeapTupleMayBeUpdated: The tuple is valid and visible, so it may be
 *	updated.
 *
 *	HeapTupleSelfUpdated: The tuple was updated by the current transaction,
 *	after the current scan started.
 *
 *	HeapTupleUpdated: The tuple was updated by a committed transaction.
 *
 *	HeapTupleBeingUpdated: The tuple is being updated by an in-progress
 *	transaction other than the current transaction.  (Note: this includes
 *	the case where the tuple is share-locked by a MultiXact, even if the
 *	MultiXact includes the current transaction.  Callers that want to
 *	distinguish that case must test for it themselves.)
 */
HTSU_Result
HeapTupleSatisfiesUpdate(HeapTuple htup, CommandId curcid,
						 Buffer buffer)
{
	HeapTupleHeader tuple = htup->t_data;

	Assert(ItemPointerIsValid(&htup->t_self));
	Assert(htup->t_tableOid != InvalidOid);

	if (!HeapTupleHeaderXminCommitted(tuple))
	{
		if (HeapTupleHeaderXminInvalid(tuple))
			return HeapTupleInvisible;

		/* Used by pre-9.0 binary upgrades */
		if (tuple->t_infomask & HEAP_MOVED_OFF)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (TransactionIdIsCurrentTransactionId(xvac))
				return HeapTupleInvisible;
			if (!TransactionIdIsInProgress(xvac))
			{
				if (TransactionIdDidCommit(xvac))
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return HeapTupleInvisible;
				}
				SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
							InvalidTransactionId);
			}
		}
		/* Used by pre-9.0 binary upgrades */
		else if (tuple->t_infomask & HEAP_MOVED_IN)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (!TransactionIdIsCurrentTransactionId(xvac))
			{
				if (TransactionIdIsInProgress(xvac))
					return HeapTupleInvisible;
				if (TransactionIdDidCommit(xvac))
					SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
								InvalidTransactionId);
				else
				{
					SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
								InvalidTransactionId);
					return HeapTupleInvisible;
				}
			}
		}
		else if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tuple)))
		{
			if (HeapTupleHeaderGetCmin(tuple) >= curcid)
				return HeapTupleInvisible;		/* inserted after scan started */

			if (tuple->t_infomask & HEAP_XMAX_INVALID)	/* xid invalid */
				return HeapTupleMayBeUpdated;

			if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
			{
				TransactionId xmax;

				xmax = HeapTupleHeaderGetRawXmax(tuple);

				/*
				 * Careful here: even though this tuple was created by our own
				 * transaction, it might be locked by other transactions, if
				 * the original version was key-share locked when we updated
				 * it.
				 */

				if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
				{
					if (MultiXactHasRunningRemoteMembers(xmax))
						return HeapTupleBeingUpdated;
					else
						return HeapTupleMayBeUpdated;
				}

				/* if locker is gone, all's well */
				if (!TransactionIdIsInProgress(xmax))
					return HeapTupleMayBeUpdated;

				if (!TransactionIdIsCurrentTransactionId(xmax))
					return HeapTupleBeingUpdated;
				else
					return HeapTupleMayBeUpdated;
			}

			if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
			{
				TransactionId xmax;

				xmax = HeapTupleGetUpdateXid(tuple);

				/* not LOCKED_ONLY, so it has to have an xmax */
				Assert(TransactionIdIsValid(xmax));

				/* updating subtransaction must have aborted */
				if (!TransactionIdIsCurrentTransactionId(xmax))
				{
					if (MultiXactHasRunningRemoteMembers(HeapTupleHeaderGetRawXmax(tuple)))
						return HeapTupleBeingUpdated;
					return HeapTupleMayBeUpdated;
				}
				else
				{
					if (HeapTupleHeaderGetCmax(tuple) >= curcid)
						return HeapTupleSelfUpdated;	/* updated after scan
														 * started */
					else
						return HeapTupleInvisible;		/* updated before scan
														 * started */
				}
			}

			if (!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
			{
				/* deleting subtransaction must have aborted */
				SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
							InvalidTransactionId);
				return HeapTupleMayBeUpdated;
			}

			if (HeapTupleHeaderGetCmax(tuple) >= curcid)
				return HeapTupleSelfUpdated;	/* updated after scan started */
			else
				return HeapTupleInvisible;		/* updated before scan started */
		}
		else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
			return HeapTupleInvisible;
		else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
			SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
						HeapTupleHeaderGetRawXmin(tuple));
		else
		{
			/* it must have aborted or crashed */
			SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
						InvalidTransactionId);
			return HeapTupleInvisible;
		}
	}

	/* by here, the inserting transaction has committed */

	if (tuple->t_infomask & HEAP_XMAX_INVALID)	/* xid invalid or aborted */
		return HeapTupleMayBeUpdated;

	if (tuple->t_infomask & HEAP_XMAX_COMMITTED)
	{
		if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
			return HeapTupleMayBeUpdated;
		return HeapTupleUpdated;	/* updated by other */
	}

	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
	{
		TransactionId xmax;

		if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
		{
			/*
			 * If it's only locked but neither EXCL_LOCK nor KEYSHR_LOCK is
			 * set, it cannot possibly be running.  Otherwise need to check.
			 */
			if ((tuple->t_infomask & (HEAP_XMAX_EXCL_LOCK |
									  HEAP_XMAX_KEYSHR_LOCK)) &&
				MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
				return HeapTupleBeingUpdated;

			SetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId);
			return HeapTupleMayBeUpdated;
		}

		xmax = HeapTupleGetUpdateXid(tuple);

		/* not LOCKED_ONLY, so it has to have an xmax */
		Assert(TransactionIdIsValid(xmax));

		if (TransactionIdIsCurrentTransactionId(xmax))
		{
			if (HeapTupleHeaderGetCmax(tuple) >= curcid)
				return HeapTupleSelfUpdated;	/* updated after scan started */
			else
				return HeapTupleInvisible;		/* updated before scan started */
		}

		if (TransactionIdIsInProgress(xmax))
			return HeapTupleBeingUpdated;

		if (TransactionIdDidCommit(xmax))
			return HeapTupleUpdated;

		/*
		 * By here, the update in the Xmax is either aborted or crashed, but
		 * what about the other members?
		 */

		if (!MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
		{
			/*
			 * There's no member, even just a locker, alive anymore, so we can
			 * mark the Xmax as invalid.
			 */
			SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
						InvalidTransactionId);
			return HeapTupleMayBeUpdated;
		}
		else
		{
			/* There are lockers running */
			return HeapTupleBeingUpdated;
		}
	}

	if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
	{
		if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
			return HeapTupleMayBeUpdated;
		if (HeapTupleHeaderGetCmax(tuple) >= curcid)
			return HeapTupleSelfUpdated;		/* updated after scan started */
		else
			return HeapTupleInvisible;	/* updated before scan started */
	}

	if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
		return HeapTupleBeingUpdated;

	if (!TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
	{
		/* it must have aborted or crashed */
		SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
					InvalidTransactionId);
		return HeapTupleMayBeUpdated;
	}

	/* xmax transaction committed */

	if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
	{
		SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
					InvalidTransactionId);
		return HeapTupleMayBeUpdated;
	}

	SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
				HeapTupleHeaderGetRawXmax(tuple));
	return HeapTupleUpdated;	/* updated by other */
}
Beispiel #7
0
/*
 * See the comments for HeapTupleSatisfiesMVCC for the semantics this function
 * obeys.
 *
 * Only usable on tuples from catalog tables!
 *
 * We don't need to support HEAP_MOVED_(IN|OFF) for now because we only support
 * reading catalog pages which couldn't have been created in an older version.
 *
 * We don't set any hint bits in here as it seems unlikely to be beneficial as
 * those should already be set by normal access and it seems to be too
 * dangerous to do so as the semantics of doing so during timetravel are more
 * complicated than when dealing "only" with the present.
 */
bool
HeapTupleSatisfiesHistoricMVCC(HeapTuple htup, Snapshot snapshot,
							   Buffer buffer)
{
	HeapTupleHeader tuple = htup->t_data;
	TransactionId xmin = HeapTupleHeaderGetXmin(tuple);
	TransactionId xmax = HeapTupleHeaderGetRawXmax(tuple);

	Assert(ItemPointerIsValid(&htup->t_self));
	Assert(htup->t_tableOid != InvalidOid);

	/* inserting transaction aborted */
	if (HeapTupleHeaderXminInvalid(tuple))
	{
		Assert(!TransactionIdDidCommit(xmin));
		return false;
	}
	/* check if it's one of our txids, toplevel is also in there */
	else if (TransactionIdInArray(xmin, snapshot->subxip, snapshot->subxcnt))
	{
		bool		resolved;
		CommandId	cmin = HeapTupleHeaderGetRawCommandId(tuple);
		CommandId	cmax = InvalidCommandId;

		/*
		 * another transaction might have (tried to) delete this tuple or
		 * cmin/cmax was stored in a combocid. So we need to lookup the actual
		 * values externally.
		 */
		resolved = ResolveCminCmaxDuringDecoding(HistoricSnapshotGetTupleCids(), snapshot,
												 htup, buffer,
												 &cmin, &cmax);

		if (!resolved)
			elog(ERROR, "could not resolve cmin/cmax of catalog tuple");

		Assert(cmin != InvalidCommandId);

		if (cmin >= snapshot->curcid)
			return false;		/* inserted after scan started */
		/* fall through */
	}
	/* committed before our xmin horizon. Do a normal visibility check. */
	else if (TransactionIdPrecedes(xmin, snapshot->xmin))
	{
		Assert(!(HeapTupleHeaderXminCommitted(tuple) &&
				 !TransactionIdDidCommit(xmin)));

		/* check for hint bit first, consult clog afterwards */
		if (!HeapTupleHeaderXminCommitted(tuple) &&
			!TransactionIdDidCommit(xmin))
			return false;
		/* fall through */
	}
	/* beyond our xmax horizon, i.e. invisible */
	else if (TransactionIdFollowsOrEquals(xmin, snapshot->xmax))
	{
		return false;
	}
	/* check if it's a committed transaction in [xmin, xmax) */
	else if (TransactionIdInArray(xmin, snapshot->xip, snapshot->xcnt))
	{
		/* fall through */
	}

	/*
	 * none of the above, i.e. between [xmin, xmax) but hasn't committed. I.e.
	 * invisible.
	 */
	else
	{
		return false;
	}

	/* at this point we know xmin is visible, go on to check xmax */

	/* xid invalid or aborted */
	if (tuple->t_infomask & HEAP_XMAX_INVALID)
		return true;
	/* locked tuples are always visible */
	else if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
		return true;

	/*
	 * We can see multis here if we're looking at user tables or if somebody
	 * SELECT ... FOR SHARE/UPDATE a system table.
	 */
	else if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
	{
		xmax = HeapTupleGetUpdateXid(tuple);
	}

	/* check if it's one of our txids, toplevel is also in there */
	if (TransactionIdInArray(xmax, snapshot->subxip, snapshot->subxcnt))
	{
		bool		resolved;
		CommandId	cmin;
		CommandId	cmax = HeapTupleHeaderGetRawCommandId(tuple);

		/* Lookup actual cmin/cmax values */
		resolved = ResolveCminCmaxDuringDecoding(HistoricSnapshotGetTupleCids(), snapshot,
												 htup, buffer,
												 &cmin, &cmax);

		if (!resolved)
			elog(ERROR, "could not resolve combocid to cmax");

		Assert(cmax != InvalidCommandId);

		if (cmax >= snapshot->curcid)
			return true;		/* deleted after scan started */
		else
			return false;		/* deleted before scan started */
	}
	/* below xmin horizon, normal transaction state is valid */
	else if (TransactionIdPrecedes(xmax, snapshot->xmin))
	{
		Assert(!(tuple->t_infomask & HEAP_XMAX_COMMITTED &&
				 !TransactionIdDidCommit(xmax)));

		/* check hint bit first */
		if (tuple->t_infomask & HEAP_XMAX_COMMITTED)
			return false;

		/* check clog */
		return !TransactionIdDidCommit(xmax);
	}
	/* above xmax horizon, we cannot possibly see the deleting transaction */
	else if (TransactionIdFollowsOrEquals(xmax, snapshot->xmax))
		return true;
	/* xmax is between [xmin, xmax), check known committed array */
	else if (TransactionIdInArray(xmax, snapshot->xip, snapshot->xcnt))
		return false;
	/* xmax is between [xmin, xmax), but known not to have committed yet */
	else
		return true;
}
Beispiel #8
0
/*
 * HeapTupleSatisfiesVacuum
 *
 *	Determine the status of tuples for VACUUM purposes.  Here, what
 *	we mainly want to know is if a tuple is potentially visible to *any*
 *	running transaction.  If so, it can't be removed yet by VACUUM.
 *
 * OldestXmin is a cutoff XID (obtained from GetOldestXmin()).  Tuples
 * deleted by XIDs >= OldestXmin are deemed "recently dead"; they might
 * still be visible to some open transaction, so we can't remove them,
 * even if we see that the deleting transaction has committed.
 */
HTSV_Result
HeapTupleSatisfiesVacuum(HeapTuple htup, TransactionId OldestXmin,
						 Buffer buffer)
{
	HeapTupleHeader tuple = htup->t_data;

	Assert(ItemPointerIsValid(&htup->t_self));
	Assert(htup->t_tableOid != InvalidOid);

	/*
	 * Has inserting transaction committed?
	 *
	 * If the inserting transaction aborted, then the tuple was never visible
	 * to any other transaction, so we can delete it immediately.
	 */
	if (!HeapTupleHeaderXminCommitted(tuple))
	{
		if (HeapTupleHeaderXminInvalid(tuple))
			return HEAPTUPLE_DEAD;
		/* Used by pre-9.0 binary upgrades */
		else if (tuple->t_infomask & HEAP_MOVED_OFF)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (TransactionIdIsCurrentTransactionId(xvac))
				return HEAPTUPLE_DELETE_IN_PROGRESS;
			if (TransactionIdIsInProgress(xvac))
				return HEAPTUPLE_DELETE_IN_PROGRESS;
			if (TransactionIdDidCommit(xvac))
			{
				SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
							InvalidTransactionId);
				return HEAPTUPLE_DEAD;
			}
			SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
						InvalidTransactionId);
		}
		/* Used by pre-9.0 binary upgrades */
		else if (tuple->t_infomask & HEAP_MOVED_IN)
		{
			TransactionId xvac = HeapTupleHeaderGetXvac(tuple);

			if (TransactionIdIsCurrentTransactionId(xvac))
				return HEAPTUPLE_INSERT_IN_PROGRESS;
			if (TransactionIdIsInProgress(xvac))
				return HEAPTUPLE_INSERT_IN_PROGRESS;
			if (TransactionIdDidCommit(xvac))
				SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
							InvalidTransactionId);
			else
			{
				SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
							InvalidTransactionId);
				return HEAPTUPLE_DEAD;
			}
		}
		else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
		{
			if (tuple->t_infomask & HEAP_XMAX_INVALID)	/* xid invalid */
				return HEAPTUPLE_INSERT_IN_PROGRESS;
			/* only locked? run infomask-only check first, for performance */
			if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask) ||
				HeapTupleHeaderIsOnlyLocked(tuple))
				return HEAPTUPLE_INSERT_IN_PROGRESS;
			/* inserted and then deleted by same xact */
			return HEAPTUPLE_DELETE_IN_PROGRESS;
		}
		else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
			SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
						HeapTupleHeaderGetRawXmin(tuple));
		else
		{
			/*
			 * Not in Progress, Not Committed, so either Aborted or crashed
			 */
			SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
						InvalidTransactionId);
			return HEAPTUPLE_DEAD;
		}

		/*
		 * At this point the xmin is known committed, but we might not have
		 * been able to set the hint bit yet; so we can no longer Assert that
		 * it's set.
		 */
	}

	/*
	 * Okay, the inserter committed, so it was good at some point.  Now what
	 * about the deleting transaction?
	 */
	if (tuple->t_infomask & HEAP_XMAX_INVALID)
		return HEAPTUPLE_LIVE;

	if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
	{
		/*
		 * "Deleting" xact really only locked it, so the tuple is live in any
		 * case.  However, we should make sure that either XMAX_COMMITTED or
		 * XMAX_INVALID gets set once the xact is gone, to reduce the costs of
		 * examining the tuple for future xacts.  Also, marking dead
		 * MultiXacts as invalid here provides defense against MultiXactId
		 * wraparound (see also comments in heap_freeze_tuple()).
		 */
		if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
		{
			if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
			{
				/*
				 * If it's only locked but neither EXCL_LOCK nor KEYSHR_LOCK
				 * are set, it cannot possibly be running; otherwise have to
				 * check.
				 */
				if ((tuple->t_infomask & (HEAP_XMAX_EXCL_LOCK |
										  HEAP_XMAX_KEYSHR_LOCK)) &&
					MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
					return HEAPTUPLE_LIVE;
				SetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId);

			}
			else
			{
				if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
					return HEAPTUPLE_LIVE;
				SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
							InvalidTransactionId);
			}
		}

		/*
		 * We don't really care whether xmax did commit, abort or crash. We
		 * know that xmax did lock the tuple, but it did not and will never
		 * actually update it.
		 */

		return HEAPTUPLE_LIVE;
	}

	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
	{
		TransactionId xmax;

		if (MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
		{
			/* already checked above */
			Assert(!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask));

			xmax = HeapTupleGetUpdateXid(tuple);

			/* not LOCKED_ONLY, so it has to have an xmax */
			Assert(TransactionIdIsValid(xmax));

			if (TransactionIdIsInProgress(xmax))
				return HEAPTUPLE_DELETE_IN_PROGRESS;
			else if (TransactionIdDidCommit(xmax))
				/* there are still lockers around -- can't return DEAD here */
				return HEAPTUPLE_RECENTLY_DEAD;
			/* updating transaction aborted */
			return HEAPTUPLE_LIVE;
		}

		Assert(!(tuple->t_infomask & HEAP_XMAX_COMMITTED));

		xmax = HeapTupleGetUpdateXid(tuple);

		/* not LOCKED_ONLY, so it has to have an xmax */
		Assert(TransactionIdIsValid(xmax));

		/* multi is not running -- updating xact cannot be */
		Assert(!TransactionIdIsInProgress(xmax));
		if (TransactionIdDidCommit(xmax))
		{
			if (!TransactionIdPrecedes(xmax, OldestXmin))
				return HEAPTUPLE_RECENTLY_DEAD;
			else
				return HEAPTUPLE_DEAD;
		}

		/*
		 * Not in Progress, Not Committed, so either Aborted or crashed.
		 * Remove the Xmax.
		 */
		SetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId);
		return HEAPTUPLE_LIVE;
	}

	if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
	{
		if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
			return HEAPTUPLE_DELETE_IN_PROGRESS;
		else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
			SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
						HeapTupleHeaderGetRawXmax(tuple));
		else
		{
			/*
			 * Not in Progress, Not Committed, so either Aborted or crashed
			 */
			SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
						InvalidTransactionId);
			return HEAPTUPLE_LIVE;
		}

		/*
		 * At this point the xmax is known committed, but we might not have
		 * been able to set the hint bit yet; so we can no longer Assert that
		 * it's set.
		 */
	}

	/*
	 * Deleter committed, but perhaps it was recent enough that some open
	 * transactions could still see the tuple.
	 */
	if (!TransactionIdPrecedes(HeapTupleHeaderGetRawXmax(tuple), OldestXmin))
		return HEAPTUPLE_RECENTLY_DEAD;

	/* Otherwise, it's dead and removable */
	return HEAPTUPLE_DEAD;
}
Beispiel #9
0
/*
 * Disallow use of an uncommitted pg_enum tuple.
 *
 * We need to make sure that uncommitted enum values don't get into indexes.
 * If they did, and if we then rolled back the pg_enum addition, we'd have
 * broken the index because value comparisons will not work reliably without
 * an underlying pg_enum entry.  (Note that removal of the heap entry
 * containing an enum value is not sufficient to ensure that it doesn't appear
 * in upper levels of indexes.)  To do this we prevent an uncommitted row from
 * being used for any SQL-level purpose.  This is stronger than necessary,
 * since the value might not be getting inserted into a table or there might
 * be no index on its column, but it's easy to enforce centrally.
 *
 * However, it's okay to allow use of uncommitted values belonging to enum
 * types that were themselves created in the same transaction, because then
 * any such index would also be new and would go away altogether on rollback.
 * (This case is required by pg_upgrade.)
 *
 * This function needs to be called (directly or indirectly) in any of the
 * functions below that could return an enum value to SQL operations.
 */
static void
check_safe_enum_use(HeapTuple enumval_tup)
{
	TransactionId xmin;
	Form_pg_enum en;
	HeapTuple	enumtyp_tup;

	/*
	 * If the row is hinted as committed, it's surely safe.  This provides a
	 * fast path for all normal use-cases.
	 */
	if (HeapTupleHeaderXminCommitted(enumval_tup->t_data))
		return;

	/*
	 * Usually, a row would get hinted as committed when it's read or loaded
	 * into syscache; but just in case not, let's check the xmin directly.
	 */
	xmin = HeapTupleHeaderGetXmin(enumval_tup->t_data);
	if (!TransactionIdIsInProgress(xmin) &&
		TransactionIdDidCommit(xmin))
		return;

	/* It is a new enum value, so check to see if the whole enum is new */
	en = (Form_pg_enum) GETSTRUCT(enumval_tup);
	enumtyp_tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(en->enumtypid));
	if (!HeapTupleIsValid(enumtyp_tup))
		elog(ERROR, "cache lookup failed for type %u", en->enumtypid);

	/*
	 * We insist that the type have been created in the same (sub)transaction
	 * as the enum value.  It would be safe to allow the type's originating
	 * xact to be a subcommitted child of the enum value's xact, but not vice
	 * versa (since we might now be in a subxact of the type's originating
	 * xact, which could roll back along with the enum value's subxact).  The
	 * former case seems a sufficiently weird usage pattern as to not be worth
	 * spending code for, so we're left with a simple equality check.
	 *
	 * We also insist that the type's pg_type row not be HEAP_UPDATED.  If it
	 * is, we can't tell whether the row was created or only modified in the
	 * apparent originating xact, so it might be older than that xact.  (We do
	 * not worry whether the enum value is HEAP_UPDATED; if it is, we might
	 * think it's too new and throw an unnecessary error, but we won't allow
	 * an unsafe case.)
	 */
	if (xmin == HeapTupleHeaderGetXmin(enumtyp_tup->t_data) &&
		!(enumtyp_tup->t_data->t_infomask & HEAP_UPDATED))
	{
		/* same (sub)transaction, so safe */
		ReleaseSysCache(enumtyp_tup);
		return;
	}

	/*
	 * There might well be other tests we could do here to narrow down the
	 * unsafe conditions, but for now just raise an exception.
	 */
	ereport(ERROR,
			(errcode(ERRCODE_UNSAFE_NEW_ENUM_VALUE_USAGE),
			 errmsg("unsafe use of new value \"%s\" of enum type %s",
					NameStr(en->enumlabel),
					format_type_be(en->enumtypid)),
	 errhint("New enum values must be committed before they can be used.")));
}