Message-ID: <c638c39b-de93-46a4-b7e9-e5613952fcb3@iki.fi>
Date: Thu, 10 Sep 2026 17:12:31 +0300
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From: Heikki Linnakangas <hlinnaka@iki.fi>
Subject: Detaching a child table makes an expression using it unrestorable
To: "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
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I bumped into a sequence of commands that breaks pg_dump & restore:

------------
create table at_tab (a int, b int);
create table at_tab_child (a int, b int);
alter table at_tab_child inherit at_tab;

-- You can use the child's rowtype in the DEFAULT without a cast.
CREATE FUNCTION func_with_default(
   arg at_tab DEFAULT ('(1, 2)'::at_tab_child)
) RETURNS integer LANGUAGE plpgsql as $$
begin
   return arg.b;
end;
$$;

-- We allow detaching the child from the parent, despite the DEFAULT
-- expression. That is a not good, because if you try to recreate the
-- function, it's not accepted. I.e. pg_dump & restore is broken
alter table at_tab_child no inherit at_tab;
------------

The function still works after that. But if you run pg_dump (or do \ef 
or something), the CREATE FUNCTION is deparsed as above, and when you 
try to restore it you get an error:

ERROR:  argument of DEFAULT must be type at_tab, not type at_tab_child
LINE 1: ...CTION public.func_with_default(arg at_tab DEFAULT '(1,2)'::a...

You get the same effect with ATTACH/DETACH PARTITION instead of 
INHERIT/NO INHERIT.

- Heikki