From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alexander Lakhin <exclusion@gmail.com>
cc: jian he <jian.universality@gmail.com>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: bug when apply fast default mechanism for adding new column over
 domain with default value
In-reply-to: <025a3ffa-5eff-4a88-97fb-8f583b015965@gmail.com>
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Comments: In-reply-to Alexander Lakhin <exclusion@gmail.com>
	message dated "Tue, 01 Apr 2025 21:00:00 +0300"
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Date: Tue, 01 Apr 2025 21:05:48 -0400
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Alexander Lakhin <exclusion@gmail.com> writes:
> I've discovered that 95f650674 introduced a defect similar to bug #18297,
> but this time with DEFAULT. Namely, the following script:
> CREATE TABLE a (aa text);
> CREATE TABLE c (cc text) INHERITS (a);
> CREATE TABLE d (dd text) INHERITS (c, a);
> ALTER TABLE a ADD COLUMN i int DEFAULT 1;

> fails with:
> ERROR:  XX000: tuple already updated by self
> LOCATION:  simple_heap_update, heapam.c:4421

Hmm, yeah.  The failing call is here:

            /* Bump the existing child att's inhcount */
	    ...
            CatalogTupleUpdate(attrdesc, &tuple->t_self, tuple);

so I think you're right that that code path is now short a
CommandCounterIncrement() somewhere.  I'll look tomorrow if
nobody beats me to it.

			regards, tom lane