有很多可能性。最简单的方法是使用pgAdmin并从SQL窗口获取。然而，如果你想通过编程方式获得这些，那么检查pg_proc和pg_trigger系统目录或例程，并从信息模式中触发视图(这是SQL的标准方式，但它可能不包括所有特性，特别是特定于postgresql的特性)。例如:

SELECT
    routine_definition 
FROM
    information_schema.routines 
WHERE
    specific_schema LIKE 'public'
    AND routine_name LIKE 'functionName';

\sf function_name在PSQL中产生单个函数的可编辑源代码。

从https://www.postgresql.org/docs/9.6/static/app-psql.html:

\ [+] function_description瑞士法郎 该命令以CREATE或REPLACE function命令的形式获取并显示命名函数的定义。 如果将+追加到命令名后，则输出行编号，函数体的第一行为第1行。

下面是一些来自PostgreSQL-9.5的例子

显示列表:

功能:\ df + 触发器:\dy+

显示的定义:

postgres=# \sf
function name is required

postgres=# \sf pg_reload_conf()
CREATE OR REPLACE FUNCTION pg_catalog.pg_reload_conf()
 RETURNS boolean
 LANGUAGE internal
 STRICT
AS $function$pg_reload_conf$function$

postgres=# \sf pg_encoding_to_char
CREATE OR REPLACE FUNCTION pg_catalog.pg_encoding_to_char(integer)
 RETURNS name
 LANGUAGE internal
 STABLE STRICT
AS $function$PG_encoding_to_char$function$

自版本:psql (9.6.17, server 11.6)

我已经尝试了以上所有的答案，但对我来说

postgres=> \sf jsonb_extract_path_text
CREATE OR REPLACE FUNCTION pg_catalog.jsonb_extract_path_text(from_json jsonb, VARIADIC path_elems text[])
 RETURNS text
 LANGUAGE internal
 IMMUTABLE PARALLEL SAFE STRICT
AS $function$jsonb_extract_path_text$function$



postgres=> \df+
ERROR:  column p.proisagg does not exist
LINE 6:   WHEN p.proisagg THEN 'agg'
               ^
HINT:  Perhaps you meant to reference the column "p.prolang".

Df似乎不适合我。

有很多可能性。最简单的方法是使用pgAdmin并从SQL窗口获取。然而，如果你想通过编程方式获得这些，那么检查pg_proc和pg_trigger系统目录或例程，并从信息模式中触发视图(这是SQL的标准方式，但它可能不包括所有特性，特别是特定于postgresql的特性)。例如:

SELECT
    routine_definition 
FROM
    information_schema.routines 
WHERE
    specific_schema LIKE 'public'
    AND routine_name LIKE 'functionName';

列出所有函数:

select n.nspname as function_schema,
       p.proname as function_name,
       l.lanname as function_language,
       case when l.lanname = 'internal' then p.prosrc
            else pg_get_functiondef(p.oid)
            end as definition,
       pg_get_function_arguments(p.oid) as function_arguments,
       t.typname as return_type
from pg_proc p
left join pg_namespace n on p.pronamespace = n.oid
left join pg_language l on p.prolang = l.oid
left join pg_type t on t.oid = p.prorettype 
where n.nspname not in ('pg_catalog', 'information_schema')
order by function_schema,
             function_name;

现在，如果你想在所有函数中搜索一个特定的单词或文本，确保你在函数中替换你的文本:

with tbl as (
select n.nspname as function_schema,
       p.proname as function_name,
       l.lanname as function_language,
       case when l.lanname = 'internal' then p.prosrc
            else pg_get_functiondef(p.oid)
            end as definition,
       pg_get_function_arguments(p.oid) as function_arguments,
       t.typname as return_type
from pg_proc p
left join pg_namespace n on p.pronamespace = n.oid
left join pg_language l on p.prolang = l.oid
left join pg_type t on t.oid = p.prorettype 
where n.nspname not in ('pg_catalog', 'information_schema')
)
    select *
    from tbl
    where definition ilike '%word or text you want to search%'
    order by function_schema,
             function_name;