From: Antonin Houska <ah@cybertec.at>
To: Alexander Lakhin <exclusion@gmail.com>
cc: Alvaro Herrera <alvherre@alvh.no-ip.org>,
    Amit Kapila <amit.kapila16@gmail.com>,
    "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>,
    Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
    Mihail Nikalayeu <mihailnikalayeu@gmail.com>,
    Matthias van de Meent <boekewurm+postgres@gmail.com>,
    Pg Hackers <pgsql-hackers@lists.postgresql.org>,
    Robert Treat <rob@xzilla.net>
Subject: Re: Adding REPACK [concurrently]
In-reply-to: <a38fc771-c860-4605-8c44-d16e8aff2534@gmail.com>
References: <202604072027.gazfa2zt2l2j@alvherre.pgsql>
 <a38fc771-c860-4605-8c44-d16e8aff2534@gmail.com>
Comments: In-reply-to Alexander Lakhin <exclusion@gmail.com>
   message dated "Fri, 10 Apr 2026 10:00:00 +0300."
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Date: Fri, 10 Apr 2026 12:57:47 +0200
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Alexander Lakhin <exclusion@gmail.com> wrote:

> Could you please look at an assertion failure produced by the following
> script, starting from 0d3dba38c:?
> createdb db1
> createdb db2
> 
> echo "
> CREATE TABLE t0 (a text);
> BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
> INSERT INTO t0 VALUES ('a');
> SELECT pg_sleep(1);
> " | psql db1 &
> 
> echo "
> CREATE TABLE t1 (id int PRIMARY KEY);
> CREATE TABLE t2 (id int PRIMARY KEY, a TEXT, FOREIGN KEY (id) REFERENCES t1);
> SET min_parallel_table_scan_size = 1;
> REPACK (CONCURRENTLY) t2;
> " | psql db2
> wait
> 
> It triggers for me:
> TRAP: failed Assert("TransactionIdPrecedesOrEquals(TransactionXmin, RecentXmin)"), File: "procarray.c", Line: 2071, PID: 3529520

Attached is a fix that works for me.

Nevertheless, REPACK (CONCURRENTLY) in your test goes ahead only due to commit
0d3dba38c7, which will probably be reverted [1]. Then REPACK will wait for the
transaction in the other database (db1) to complete before it can actually
start.

Thanks for the report!

[1] https://www.postgresql.org/message-id/cdgw4sbbfcgk6du3iv54r2dgiy4tfywoklbotlmj4irxavdcr3@glxfw5jj277q

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com


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