Feedback-ID: ie3de48e3:Fastmail
Date: Mon, 26 Jan 2026 15:33:37 +0100
From: =?utf-8?Q?=C3=81lvaro?= Herrera <alvherre@kurilemu.de>
To: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Cc: yanliang lei <msdnchina@163.com>, pgsql-bugs@lists.postgresql.org
Subject: Re: Re: Re: BUG #19351: in pg18.1,when not null exists in the table
 , and add constraint problem.
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Hello,

On 2026-Jan-26, Srinath Reddy Sadipiralla wrote:

> i looked into this,

Thank you!

> the reason for these failures was when the given name for a constraint
> for a parent table propagates to the child table because of
> inheritance the name conflicts and throws "mismatching constraint
> name" error we added,

Right, that's what I saw.

> I think we can fix this by throwing an error only if this constraint
> was added directly to the table and not through
> inheritance/propagation from the parent, we can do this using the
> "is_local" flag, i have checked and all tests passed.

Hmm, I'm not opposed to this; does it change any other behavior?  I
think it's important to see whether there are other corner cases that
would react to this behavior change.  For example, what would happen if
two existing parents have a not-null constraint on the same column?  Is
there a change for combined LIKE and regular inheritance?  I think we
should have reasonable reactions to each of those scenarios:

create table parent (a int not null);
create table parent2 (a int not null);

create table child1 () inherits (parent, parent2);
create table child2 () inherits (parent2, parent);
create table child3 (not null a) inherits (parent2, parent);

create table child4 (like parent) inherits (parent2);
-- and so on as your imagination allows


Would you be able to send a patch based on this idea and what I sent
earlier?  

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Las navajas y los monos deben estar siempre distantes"   (Germán Poo)