/*
 * HeapTupleSatisfiesMVCC
 *		True iff heap tuple is valid for the given MVCC snapshot.
…
	if (!HeapTupleHeaderXminCommitted(tuple))
	{
		if (HeapTupleHeaderXminInvalid(tuple))
			return false;
…
		else if (XidInMVCCSnapshot(HeapTupleHeaderGetRawXmin(tuple), snapshot))
			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;
		}
	}
	else
	{
		/* xmin is committed, but maybe not according to our snapshot */
		if (!HeapTupleHeaderXminFrozen(tuple) &&
			XidInMVCCSnapshot(HeapTupleHeaderGetRawXmin(tuple), snapshot))
			return false;		/* treat as still in progress */
	}
…
	/* by here, the inserting transaction has committed */

	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 (XidInMVCCSnapshot(HeapTupleHeaderGetRawXmax(tuple), snapshot))
			return true;

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

	return false;

Échauffement