Message-ID: <ffe25abd1c4202efbc228bc85656ff20fdbf86ee.camel@cybertec.at>
Subject: Re: Issue with pg_get_functiondef
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Edouard Tollet <edouard.tollet@stoik.io>, pgsql-bugs@lists.postgresql.org
Date: Tue, 12 Dec 2023 13:18:49 +0100
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On Tue, 2023-12-12 at 10:33 +0100, Edouard Tollet wrote:
> I'm having trouble understanding the following, I apologize in advance if=
 it is not a bug.
> The following query works and lists the functions name and definitions as=
 set in my database:
>=20
> select * from (
> =C2=A0=C2=A0=C2=A0 select proname, prokind, pg_get_functiondef(oid) as de=
f
> =C2=A0=C2=A0=C2=A0 from pg_proc
> =C2=A0=C2=A0=C2=A0 where pg_proc.prokind =3D 'f'
> ) def
>=20
> however, if I add the filter where def is not null, it returns an error:
> select * from (
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 select proname, prokind, pg_get_functiondef(o=
id) as def
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 from pg_proc
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 where pg_proc.prokind =3D 'f'
> ) def
> where def is not null;
> ERROR: =C2=A0"array_agg" is an aggregate function

PostgreSQL evaluates the function before the WHERE clause.
Try this:

  WITH cte AS MATERIALIZED (
     SELECT proname, oid
     FROM pg_proc
     WHERE prokind =3D 'f'
  )
  SELECT proname, pg_get_functiondef(oid) AS def
  FROM cte;

Yours,
Laurenz Albe