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
pg_type.typname != 'void'
AND pronamespace = (SELECT pg_namespace.oid FROM pg_namespace WHERE nspname = 'public');

      函数名称          | 返回值数据类型 | 参数个数

_group_concat	text	2
film_in_stock	int4	2
film_not_in_stock	int4	2
last_day	date	1
last_updated	trigger	0
get_sum	numeric	2
get_customer_balance	numeric	2
inventory_held_by_customer	int4	1
inventory_in_stock	bool	1
rewards_report	customer	2
group_concat	text	1

(11 行记录)