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PostgreSQLでfunctionの定義を確認する方法

チェック対象の関数(function)

DROP FUNCTION IF EXISTS years_ago(INTEGER);

CREATE OR REPLACE FUNCTION years_ago(INTEGER)
RETURNS INTEGER AS $$
  SELECT (extract(year from current_date)::INTEGER - first_appeared)
  FROM programming
  WHERE id = $1;
$$ LANGUAGE sql;

方法1 : pg_proc の prosrcを使用

SELECT proname, prosrc FROM pg_proc WHERE proname = 'years_ago';

postgres=# SELECT proname, prosrc FROM pg_proc WHERE proname = 'years_ago';
  proname  |                                prosrc                                
-----------+----------------------------------------------------------------------
 years_ago |                                                                     +
           |   SELECT (extract(year from current_date)::INTEGER - first_appeared)+
           |   FROM programming                                                  +
           |   WHERE id = $1;                                                    +
           | 
(1 row)

方法2 : pg_get_functiondefと組み合わせて使用する

CREATE OR REPLACE FUNCTIONやその他の構文も合わせて出力してくれるので他環境に実行したい時とかに便利。

SELECT pg_get_functiondef((SELECT oid FROM pg_proc WHERE proname = 'years_ago'));

postgres=# SELECT pg_get_functiondef((SELECT oid FROM pg_proc WHERE proname = 'years_ago'));
                          pg_get_functiondef                          
----------------------------------------------------------------------
 CREATE OR REPLACE FUNCTION public.years_ago(integer)                +
  RETURNS integer                                                    +
  LANGUAGE sql                                                       +
 AS $function$                                                       +
   SELECT (extract(year from current_date)::INTEGER - first_appeared)+
   FROM programming                                                  +
   WHERE id = $1;                                                    +
 $function$                                                          +
 
(1 row)

方法3 : information_schema を使用する

SELECT routine_definition FROM information_schema.routines WHERE routine_name = 'years_ago';

postgres=# SELECT routine_definition FROM information_schema.routines WHERE routine_name = 'years_ago';
                          routine_definition                          
----------------------------------------------------------------------
                                                                     +
   SELECT (extract(year from current_date)::INTEGER - first_appeared)+
   FROM programming                                                  +
   WHERE id = $1;                                                    +
 
(1 row)
---

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#PostgreSQL