Function apply_attrmap_mutator

src/backend/executor/execMain.c:4179–4205

For attrMapExpr below. * * Mutate Var nodes in an expression using the given attribute map. * Insist the Var nodes have varno == 1 and the that the mapping * yields a live attribute number (non-zero). */

 * yields a live attribute number (non-zero).
 */
static Node *apply_attrmap_mutator(Node *node, TupleConversionMap *map)
{
	if ( node == NULL )
		return NULL;
	
	if (IsA(node, Var) )
	{
		Var		   *var = (Var *) node;
		AttrNumber anum;

		Assert(var->varno == 1); /* in CHECK constraints */
		anum = attrMap(map, var->varattno);

		if (anum == 0)
		{
			/* Should never happen, but best caught early. */
			elog(ERROR, "attribute map discrepancy");
		}
		else if (anum != var->varattno)
		{
			var = copyObject(var);
			var->varattno = anum;
		}
		return (Node *) var;
	}
	return expression_tree_mutator(node, apply_attrmap_mutator, (void *) map);
}

/* Apply attrMap over the Var nodes in an expression. */
Node *