Function MJEvalInnerValues

src/backend/executor/nodeMergejoin.c:372–410

* MJEvalInnerValues * * Same as above, but for the inner tuple. Here, we have to be prepared * to load data from either the true current inner, or the marked inner, * so caller must tell us which slot to load from. */

 * so caller must tell us which slot to load from.
 */
static MJEvalResult
MJEvalInnerValues(MergeJoinState *mergestate, TupleTableSlot *innerslot)
{
	ExprContext *econtext = mergestate->mj_InnerEContext;
	MJEvalResult result = MJEVAL_MATCHABLE;
	int			i;
	MemoryContext oldContext;

	/* Check for end of inner subplan */
	if (TupIsNull(innerslot))
		return MJEVAL_ENDOFJOIN;

	ResetExprContext(econtext);

	oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);

	econtext->ecxt_innertuple = innerslot;

	for (i = 0; i < mergestate->mj_NumClauses; i++)
	{
		MergeJoinClause clause = &mergestate->mj_Clauses[i];

		clause->rdatum = ExecEvalExpr(clause->rexpr, econtext,
									  &clause->risnull);
		if (clause->risnull && !clause->notdistinct)
		{
			/* match is impossible; can we end the join early? */
			if (i == 0 && !clause->ssup.ssup_nulls_first &&
				!mergestate->mj_FillInner)
				result = MJEVAL_ENDOFJOIN;
			else if (result == MJEVAL_MATCHABLE)
				result = MJEVAL_NONMATCHABLE;
		}
	}

	MemoryContextSwitchTo(oldContext);

	return result;
}

/*
 * MJCompare