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From: Alvaro Herrera <[email protected]>
To: Tom Lane <[email protected]>
Cc: Tender Wang <[email protected]>
Cc: jian he <[email protected]>
Cc: Pg Hackers <[email protected]>
Subject: Re: not null constraints, again
Date: Tue, 15 Apr 2025 23:10:26 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 2025-Apr-15, Tom Lane wrote:

> +1.  Fundamentally the problem here is that pg_restore needs
> 
> ALTER TABLE ONLY foo ADD PRIMARY KEY
> 
> to not recurse to child tables at all.  It is expecting this command
> to acquire a lock on foo and nothing else; and it has already taken
> care of making foo's PK column(s) NOT NULL, so there is no reason we
> should have to examine the children.

Right.

> Looking at the patch itself, it doesn't seem like the got_children
> flag is accomplishing anything; I guess that was leftover from an
> earlier version?  You could declare "List *children" inside the
> block where it's used, too.  Basically, this patch is just moving
> the check-the-children logic from one place to another.

Ah yes, I forgot to set got_children when reading the children list.
This happens within the loop for columns, so the idea is to obtain that
list just once instead of once per column.  I don't think there's any
ill effect from doing it multiple times, but it's wasted work and that's
what led me to adding got_children.  I'll add the assignment.

> Also I find the comments still a bit confusing, but maybe that's
> on me.

I'll review tomorrow morning, maybe I can find some improvements for
them.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"La conclusión que podemos sacar de esos estudios es que
no podemos sacar ninguna conclusión de ellos" (Tanenbaum)

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