Function check_sql_fn_retval

src/backend/executor/functions.c:1748–2117

* check_sql_fn_retval() * Check return value of a list of lists of sql parse trees. * * The return value of a sql function is the value returned by the last * canSetTag query in the function. We do some ad-hoc type checking and * coercion here to ensure that the function returns what it's supposed to. * Note that we may actually modify the last query to make it match! * * This function r

 * function is defined to return VOID then *resultTargetList is set to NIL.
 */
bool
check_sql_fn_retval(List *queryTreeLists,
					Oid rettype, TupleDesc rettupdesc,
					bool insertDroppedCols,
					List **resultTargetList)
{
	bool		is_tuple_result = false;
	Query	   *parse;
	ListCell   *parse_cell;
	List	   *tlist;
	int			tlistlen;
	bool		tlist_is_modifiable;
	char		fn_typtype;
	List	   *upper_tlist = NIL;
	bool		upper_tlist_nontrivial = false;
	ListCell   *lc;

	if (resultTargetList)
		*resultTargetList = NIL;	/* initialize in case of VOID result */

	/*
	 * If it's declared to return VOID, we don't care what's in the function.
	 * (This takes care of the procedure case, as well.)
	 */
	if (rettype == VOIDOID)
		return false;

	/*
	 * Find the last canSetTag query in the function body (which is presented
	 * to us as a list of sublists of Query nodes).  This isn't necessarily
	 * the last parsetree, because rule rewriting can insert queries after
	 * what the user wrote.  Note that it might not even be in the last
	 * sublist, for example if the last query rewrites to DO INSTEAD NOTHING.
	 * (It might not be unreasonable to throw an error in such a case, but
	 * this is the historical behavior and it doesn't seem worth changing.)
	 */
	parse = NULL;
	parse_cell = NULL;
	foreach(lc, queryTreeLists)
	{
		List	   *sublist = lfirst_node(List, lc);
		ListCell   *lc2;

		foreach(lc2, sublist)
		{
			Query	   *q = lfirst_node(Query, lc2);

			if (q->canSetTag)
			{
				parse = q;
				parse_cell = lc2;
			}
		}
	}

	/*
	 * If it's a plain SELECT, it returns whatever the targetlist says.
	 * Otherwise, if it's INSERT/UPDATE/DELETE with RETURNING, it returns