Example #1
0
/*
 * Add a tuple to the new heap.
 *
 * Visibility information is copied from the original tuple, except that
 * we "freeze" very-old tuples.  Note that since we scribble on new_tuple,
 * it had better be temp storage not a pointer to the original tuple.
 *
 * state		opaque state as returned by begin_heap_rewrite
 * old_tuple	original tuple in the old heap
 * new_tuple	new, rewritten tuple to be inserted to new heap
 */
void
rewrite_heap_tuple(RewriteState state,
				   HeapTuple old_tuple, HeapTuple new_tuple)
{
	MemoryContext old_cxt;
	ItemPointerData old_tid;
	TidHashKey	hashkey;
	bool		found;
	bool		free_new;

	old_cxt = MemoryContextSwitchTo(state->rs_cxt);

	/*
	 * Copy the original tuple's visibility information into new_tuple.
	 *
	 * XXX we might later need to copy some t_infomask2 bits, too? Right now,
	 * we intentionally clear the HOT status bits.
	 */
	memcpy(&new_tuple->t_data->t_choice.t_heap,
		   &old_tuple->t_data->t_choice.t_heap,
		   sizeof(HeapTupleFields));

	new_tuple->t_data->t_infomask &= ~HEAP_XACT_MASK;
	new_tuple->t_data->t_infomask2 &= ~HEAP2_XACT_MASK;
	new_tuple->t_data->t_infomask |=
		old_tuple->t_data->t_infomask & HEAP_XACT_MASK;

	/*
	 * While we have our hands on the tuple, we may as well freeze any
	 * eligible xmin or xmax, so that future VACUUM effort can be saved.
	 */
	heap_freeze_tuple(new_tuple->t_data, state->rs_freeze_xid,
					  state->rs_cutoff_multi);

	/*
	 * Invalid ctid means that ctid should point to the tuple itself. We'll
	 * override it later if the tuple is part of an update chain.
	 */
	ItemPointerSetInvalid(&new_tuple->t_data->t_ctid);

	/*
	 * If the tuple has been updated, check the old-to-new mapping hash table.
	 */
	if (!((old_tuple->t_data->t_infomask & HEAP_XMAX_INVALID) ||
		  HeapTupleHeaderIsOnlyLocked(old_tuple->t_data)) &&
		!(ItemPointerEquals(&(old_tuple->t_self),
							&(old_tuple->t_data->t_ctid))))
	{
		OldToNewMapping mapping;

		memset(&hashkey, 0, sizeof(hashkey));
		hashkey.xmin = HeapTupleHeaderGetUpdateXid(old_tuple->t_data);
		hashkey.tid = old_tuple->t_data->t_ctid;

		mapping = (OldToNewMapping)
			hash_search(state->rs_old_new_tid_map, &hashkey,
						HASH_FIND, NULL);

		if (mapping != NULL)
		{
			/*
			 * We've already copied the tuple that t_ctid points to, so we can
			 * set the ctid of this tuple to point to the new location, and
			 * insert it right away.
			 */
			new_tuple->t_data->t_ctid = mapping->new_tid;

			/* We don't need the mapping entry anymore */
			hash_search(state->rs_old_new_tid_map, &hashkey,
						HASH_REMOVE, &found);
			Assert(found);
		}
		else
		{
			/*
			 * We haven't seen the tuple t_ctid points to yet. Stash this
			 * tuple into unresolved_tups to be written later.
			 */
			UnresolvedTup unresolved;

			unresolved = hash_search(state->rs_unresolved_tups, &hashkey,
									 HASH_ENTER, &found);
			Assert(!found);

			unresolved->old_tid = old_tuple->t_self;
			unresolved->tuple = heap_copytuple(new_tuple);

			/*
			 * We can't do anything more now, since we don't know where the
			 * tuple will be written.
			 */
			MemoryContextSwitchTo(old_cxt);
			return;
		}
	}

	/*
	 * Now we will write the tuple, and then check to see if it is the B tuple
	 * in any new or known pair.  When we resolve a known pair, we will be
	 * able to write that pair's A tuple, and then we have to check if it
	 * resolves some other pair.  Hence, we need a loop here.
	 */
	old_tid = old_tuple->t_self;
	free_new = false;

	for (;;)
	{
		ItemPointerData new_tid;

		/* Insert the tuple and find out where it's put in new_heap */
		raw_heap_insert(state, new_tuple);
		new_tid = new_tuple->t_self;

		/*
		 * If the tuple is the updated version of a row, and the prior version
		 * wouldn't be DEAD yet, then we need to either resolve the prior
		 * version (if it's waiting in rs_unresolved_tups), or make an entry
		 * in rs_old_new_tid_map (so we can resolve it when we do see it). The
		 * previous tuple's xmax would equal this one's xmin, so it's
		 * RECENTLY_DEAD if and only if the xmin is not before OldestXmin.
		 */
		if ((new_tuple->t_data->t_infomask & HEAP_UPDATED) &&
			!TransactionIdPrecedes(HeapTupleHeaderGetXmin(new_tuple->t_data),
								   state->rs_oldest_xmin))
		{
			/*
			 * Okay, this is B in an update pair.  See if we've seen A.
			 */
			UnresolvedTup unresolved;

			memset(&hashkey, 0, sizeof(hashkey));
			hashkey.xmin = HeapTupleHeaderGetXmin(new_tuple->t_data);
			hashkey.tid = old_tid;

			unresolved = hash_search(state->rs_unresolved_tups, &hashkey,
									 HASH_FIND, NULL);

			if (unresolved != NULL)
			{
				/*
				 * We have seen and memorized the previous tuple already. Now
				 * that we know where we inserted the tuple its t_ctid points
				 * to, fix its t_ctid and insert it to the new heap.
				 */
				if (free_new)
					heap_freetuple(new_tuple);
				new_tuple = unresolved->tuple;
				free_new = true;
				old_tid = unresolved->old_tid;
				new_tuple->t_data->t_ctid = new_tid;

				/*
				 * We don't need the hash entry anymore, but don't free its
				 * tuple just yet.
				 */
				hash_search(state->rs_unresolved_tups, &hashkey,
							HASH_REMOVE, &found);
				Assert(found);

				/* loop back to insert the previous tuple in the chain */
				continue;
			}
			else
			{
				/*
				 * Remember the new tid of this tuple. We'll use it to set the
				 * ctid when we find the previous tuple in the chain.
				 */
				OldToNewMapping mapping;

				mapping = hash_search(state->rs_old_new_tid_map, &hashkey,
									  HASH_ENTER, &found);
				Assert(!found);

				mapping->new_tid = new_tid;
			}
		}

		/* Done with this (chain of) tuples, for now */
		if (free_new)
			heap_freetuple(new_tuple);
		break;
	}

	MemoryContextSwitchTo(old_cxt);
}
Example #2
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;
}