SELECT
  pg_proc.proname AS "函数名称",
  pg_type.typname AS "返回值数据类型",
  pg_proc.pronargs AS "参数个数"
FROM
  pg_proc
JOIN pg_type
ON (pg_proc.prorettype = pg_type.oid)
WHERE
pronamespace = (SELECT pg_namespace.oid FROM pg_namespace WHERE nspname = '模式(架构)名');