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From: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Date: Mon, 12 Jan 2026 21:54:56 +0300
Message-ID: <CADzfLwU78as45To9a=-Qkr5jEg3tMxc5rUtdKy2MTv4r_SDGng@mail.gmail.com>
Subject: Re: Adding REPACK [concurrently]
To: Antonin Houska <ah@cybertec.at>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, 
	Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
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Also, there are some crashes of stress tests for v30 (for both single
snapshot and multiple snapshot versions).

---------------------

Looks like something is leaking, but not sure.

https://cirrus-ci.com/task/5577209672368128?logs=test_world#L277 (multiple
snapshots)
https://cirrus-ci.com/task/6439044873191424 (without multiple snapshots)

[17:49:07.251] #   Failed test 'concurrent operations with REINDEX/CREATE
INDEX CONCURRENTLY stderr /(?^:^$)/'
[17:49:07.251] #   at /tmp/cirrus-ci-build/contrib/amcheck/t/
007_repack_concurrently.pl line 56.
[17:49:07.251] #                   'pgbench: error: client 0 script 0
aborted in command 6 query 0: ERROR:  out of background worker slots
[17:49:07.251] # HINT:  You might need to increase "max_worker_processes".
[17:49:07.251] # pgbench: error: Run was aborted due to an error in thread 0

-------------------

This one showed something goes wrong, the sum of the table is broken. It
may be 0 because non-MVCC safe, but I checked the logs:

2026-01-12 18:41:11.656 UTC client backend[76247] 007_repack_concurrently.pl
LOG:  statement: SELECT (490588) / 0;

And also

backend[54349] 007_repack_concurrently.pl ERROR:  could not create unique
index "tbl_pkey_repacknew"
2026-01-12 18:41:12.477 UTC client backend[54349] 007_repack_concurrently.pl
DETAIL:  Key (i)=(942) is duplicated.
2026-01-12 18:41:12.477 UTC client backend[54349] 007_repack_concurrently.pl
STATEMENT:  REPACK (CONCURRENTLY) tbl;

https://cirrus-ci.com/task/4521496594350080 (single snapshot version)
https://cirrus-ci.com/task/6157569896480768 (single snapshot version)

[18:36:17.466] #   at /Users/admin/pgsql/contrib/amcheck/t/
007_repack_concurrently.pl line 56.
[18:36:17.466] #                   'pgbench: error: client 21 script 0
aborted in command 31 query 0: ERROR:  division by zero
[18:36:17.466] # pgbench: error: Run was aborted due to an error in thread 2

---------------------

https://cirrus-ci.com/task/5682762788634624 (multiple snapshots)

 Failed test 'concurrent operations with REINDEX/CREATE INDEX CONCURRENTLY
stderr /(?^:^$)/'
[18:02:06.938] #   at t/007_repack_concurrently.pl line 56.
[18:02:06.938] #                   'pgbench: error: client 6 aborted in
command 4 (SQL) of script 0; perhaps the backend died while processing
[18:02:06.938] # pgbench: error: Run was aborted due to an error in thread 0
[18:02:06.938] # WARNING:  terminating connection because of crash of
another server process

Best regards,
Mikhail.

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<div dir=3D"ltr">Also, there are some crashes of stress tests for v30 (for =
both single snapshot and multiple snapshot versions).<br><br>--------------=
-------<div><br></div><div>Looks like something is leaking, but not sure.<b=
r><div><br><a href=3D"https://cirrus-ci.com/task/5577209672368128?logs=3Dte=
st_world#L277">https://cirrus-ci.com/task/5577209672368128?logs=3Dtest_worl=
d#L277</a> (multiple snapshots)<div><a href=3D"https://cirrus-ci.com/task/6=
439044873191424">https://cirrus-ci.com/task/6439044873191424</a> (without m=
ultiple snapshots)<br><div><br></div><div>[17:49:07.251] # =C2=A0 Failed te=
st &#39;concurrent operations with REINDEX/CREATE INDEX CONCURRENTLY stderr=
 /(?^:^$)/&#39;<br>[17:49:07.251] # =C2=A0 at /tmp/cirrus-ci-build/contrib/=
amcheck/t/<a href=3D"http://007_repack_concurrently.pl">007_repack_concurre=
ntly.pl</a> line 56.<br>[17:49:07.251] # =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0 =C2=A0 =C2=A0 =C2=A0 &#39;pgbench: error: client 0 script 0 aborted=
 in command 6 query 0: ERROR: =C2=A0out of background worker slots<br>[17:4=
9:07.251] # HINT: =C2=A0You might need to increase &quot;max_worker_process=
es&quot;.<br>[17:49:07.251] # pgbench: error: Run was aborted due to an err=
or in thread 0</div><div><br></div><div>-------------------</div><div><br><=
/div><div>This one showed something goes wrong, the sum of the table is bro=
ken. It may be 0 because non-MVCC safe, but I checked the logs:</div><div><=
br></div><div>2026-01-12 18:41:11.656 UTC client backend[76247] <a href=3D"=
http://007_repack_concurrently.pl">007_repack_concurrently.pl</a> LOG: =C2=
=A0statement: SELECT (490588) / 0;<br></div><div><br></div><div>And also</d=
iv><div><br></div><div>backend[54349] <a href=3D"http://007_repack_concurre=
ntly.pl">007_repack_concurrently.pl</a> ERROR: =C2=A0could not create uniqu=
e index &quot;tbl_pkey_repacknew&quot;<br>2026-01-12 18:41:12.477 UTC clien=
t backend[54349] <a href=3D"http://007_repack_concurrently.pl">007_repack_c=
oncurrently.pl</a> DETAIL: =C2=A0Key (i)=3D(942) is duplicated.<br>2026-01-=
12 18:41:12.477 UTC client backend[54349] <a href=3D"http://007_repack_conc=
urrently.pl">007_repack_concurrently.pl</a> STATEMENT: =C2=A0REPACK (CONCUR=
RENTLY) tbl;</div><div><br></div><div><a href=3D"https://cirrus-ci.com/task=
/4521496594350080">https://cirrus-ci.com/task/4521496594350080</a> (single =
snapshot version)</div><div><a href=3D"https://cirrus-ci.com/task/615756989=
6480768">https://cirrus-ci.com/task/6157569896480768</a> (single snapshot v=
ersion)</div><div><br></div><div>[18:36:17.466] # =C2=A0 at /Users/admin/pg=
sql/contrib/amcheck/t/<a href=3D"http://007_repack_concurrently.pl">007_rep=
ack_concurrently.pl</a> line 56.<br>[18:36:17.466] # =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 &#39;pgbench: error: client 21 sc=
ript 0 aborted in command 31 query 0: ERROR: =C2=A0division by zero<br>[18:=
36:17.466] # pgbench: error: Run was aborted due to an error in thread 2</d=
iv><div><br></div><div>---------------------</div><div><br></div><div><a hr=
ef=3D"https://cirrus-ci.com/task/5682762788634624">https://cirrus-ci.com/ta=
sk/5682762788634624</a> (multiple snapshots)</div><div><br></div><div>=C2=
=A0Failed test &#39;concurrent operations with REINDEX/CREATE INDEX CONCURR=
ENTLY stderr /(?^:^$)/&#39;<br>[18:02:06.938] # =C2=A0 at t/<a href=3D"http=
://007_repack_concurrently.pl">007_repack_concurrently.pl</a> line 56.<br>[=
18:02:06.938] # =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 &#39;pgbench: error: client 6 aborted in command 4 (SQL) of script 0; p=
erhaps the backend died while processing<br>[18:02:06.938] # pgbench: error=
: Run was aborted due to an error in thread 0<br>[18:02:06.938] # WARNING: =
=C2=A0terminating connection because of crash of another server process</di=
v></div></div></div><div><br></div><div>Best regards,</div><div>Mikhail.</d=
iv></div>

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