Function expandRecordVariable

src/backend/parser/parse_target.c:1512–1684

* expandRecordVariable * Get the tuple descriptor for a Var of type RECORD, if possible. * * Since no actual table or view column is allowed to have type RECORD, such * a Var must refer to a JOIN or FUNCTION RTE or to a subquery output. We * drill down to find the ultimate defining expression and attempt to infer * the tupdesc from it. We ereport if we can't determine the tupdesc. * * l

 * levelsup is an extra offset to interpret the Var's varlevelsup correctly.
 */
TupleDesc
expandRecordVariable(ParseState *pstate, Var *var, int levelsup)
{
	TupleDesc	tupleDesc;
	int			netlevelsup;
	RangeTblEntry *rte;
	AttrNumber	attnum;
	Node	   *expr;

	/* Check my caller didn't mess up */
	Assert(IsA(var, Var));
	Assert(var->vartype == RECORDOID);

	/*
	 * Note: it's tempting to use GetNSItemByRangeTablePosn here so that we
	 * can use expandNSItemVars instead of expandRTE; but that does not work
	 * for some of the recursion cases below, where we have consed up a
	 * ParseState that lacks p_namespace data.
	 */
	netlevelsup = var->varlevelsup + levelsup;
	rte = GetRTEByRangeTablePosn(pstate, var->varno, netlevelsup);
	attnum = var->varattno;

	if (attnum == InvalidAttrNumber)
	{
		/* Whole-row reference to an RTE, so expand the known fields */
		List	   *names,
				   *vars;
		ListCell   *lname,
				   *lvar;
		int			i;

		expandRTE(rte, var->varno, 0, var->location, false,
				  &names, &vars);

		tupleDesc = CreateTemplateTupleDesc(list_length(vars));
		i = 1;
		forboth(lname, names, lvar, vars)
		{
			char	   *label = strVal(lfirst(lname));
			Node	   *varnode = (Node *) lfirst(lvar);

			TupleDescInitEntry(tupleDesc, i,
							   label,
							   exprType(varnode),
							   exprTypmod(varnode),
							   0);
			TupleDescInitEntryCollation(tupleDesc, i,
										exprCollation(varnode));
			i++;
		}
		Assert(lname == NULL && lvar == NULL);	/* lists same length? */

		return tupleDesc;
	}

	expr = (Node *) var;		/* default if we can't drill down */