Function ExecEvalWholeRowVar

src/backend/executor/execExprInterp.c:4172–4397

* Evaluate a wholerow Var expression. * * Returns a Datum whose value is the value of a whole-row range variable * with respect to given expression context. */

 * with respect to given expression context.
 */
void
ExecEvalWholeRowVar(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
	Var		   *variable = op->d.wholerow.var;
	TupleTableSlot *slot;
	TupleDesc	output_tupdesc;
	MemoryContext oldcontext;
	HeapTupleHeader dtuple;
	HeapTuple	tuple;

	/* This was checked by ExecInitExpr */
	Assert(variable->varattno == InvalidAttrNumber);

	/* Get the input slot we want */
	switch (variable->varno)
	{
		case INNER_VAR:
			/* get the tuple from the inner node */
			slot = econtext->ecxt_innertuple;
			break;

		case OUTER_VAR:
			/* get the tuple from the outer node */
			slot = econtext->ecxt_outertuple;
			break;

			/* INDEX_VAR is handled by default case */

		default:
			/* get the tuple from the relation being scanned */
			slot = econtext->ecxt_scantuple;
			break;
	}

	/* Apply the junkfilter if any */
	if (op->d.wholerow.junkFilter != NULL)
		slot = ExecFilterJunk(op->d.wholerow.junkFilter, slot);

	/*
	 * If first time through, obtain tuple descriptor and check compatibility.
	 *
	 * XXX: It'd be great if this could be moved to the expression
	 * initialization phase, but due to using slots that's currently not
	 * feasible.
	 */
	if (op->d.wholerow.first)
	{
		/* optimistically assume we don't need slow path */
		op->d.wholerow.slow = false;

		/*
		 * If the Var identifies a named composite type, we must check that
		 * the actual tuple type is compatible with it.
		 */
		if (variable->vartype != RECORDOID)
		{
			TupleDesc	var_tupdesc;
			TupleDesc	slot_tupdesc;