Function function_exists

src/backend/utils/cache/lsyscache.c:4084–4088

* function_exists * Is there a function with the given oid */

 *	  Is there a function with the given oid
 */
bool
function_exists(Oid oid)
{
	return SearchSysCacheExists(PROCOID, oid, 0, 0, 0);
}

/*
 * aggregate_exists