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Message-ID: <d704cde4-b1f2-48dc-8c5e-659d1128d286@gmail.com>
Date: Tue, 29 Sep 2026 23:00:00 +0300
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User-Agent: Mozilla Thunderbird
Subject: Re: REPACK (CONCURRENTLY) can crash a logical decoding session
To: Masahiko Sawada <sawada.mshk@gmail.com>,
 =?UTF-8?Q?=C3=81lvaro_Herrera?= <alvherre@kurilemu.de>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>,
 Thom Brown <thom@linux.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
 Antonin Houska <ah@cybertec.at>
References: 
 <CAD21AoC8tp3Dq3Bq3T7_0C0dNWRBSbADQez7kMp1gdcazB+neQ@mail.gmail.com>
 <aqPtaPNZdskc83gS@alvherre.pgsql>
 <CAD21AoBKZi3f5p3FYWehDQcWOoBszyedHgbXZMp-3F1h=K9hPQ@mail.gmail.com>
Content-Language: en-US
From: Alexander Lakhin <exclusion@gmail.com>
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 <CAD21AoBKZi3f5p3FYWehDQcWOoBszyedHgbXZMp-3F1h=K9hPQ@mail.gmail.com>
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Hello Sawada-san,

11.09.2026 20:56, Masahiko Sawada wrote:
>> No objections here -- they look good to me too.  The isolation spec
>> addition is great, thanks.
> Thank you for looking at the patches! Pushed.

A recent failure of repack_decode.spec emitted by skink [1]:
# diff -U3 /home/bf/bf-build/skink-master/HEAD/pgsql/src/test/modules/injection_points/expected/repack_decode.out 
/home/bf/bf-build/skink-master/HEAD/pgsql.build/testrun/injection_points/isolation/results/repack_decode.out
# --- /home/bf/bf-build/skink-master/HEAD/pgsql/src/test/modules/injection_points/expected/repack_decode.out 2026-09-25 
23:32:42.088355239 +0200
# +++ /home/bf/bf-build/skink-master/HEAD/pgsql.build/testrun/injection_points/isolation/results/repack_decode.out 
2026-09-29 18:01:56.818281263 +0200
# @@ -26,7 +26,7 @@
#
#  count
#  -----
# -    8
# +   12
#  (1 row)
#
#  injection_points_detach
# 1 of 16 tests failed.

apparently shows that the test is not immune to autovacuum.

I can reproduce such failures locally with:
--- a/src/test/modules/injection_points/Makefile
+++ b/src/test/modules/injection_points/Makefile
@@ -21,3 +21,3 @@ ISOLATION = basic \
             repack_commit_race \
-           repack_decode \
+           $(shell printf 'repack_decode %.0s' `seq 100`) \
             repack_missingval \

and
echo "autovacuum_naptime = 1" >/tmp/temp.config
TEMP_CONFIG=/tmp/temp.config make -s check -C src/test/modules/injection_points/
...
ok 9         - repack_decode                             272 ms
# diff -U3 .../src/test/modules/injection_points/expected/repack_decode.out 
.../src/test/modules/injection_points/output_iso/results/repack_decode.out
# --- .../src/test/modules/injection_points/expected/repack_decode.out 2026-09-29 14:51:55.810851901 -0400
# +++ .../src/test/modules/injection_points/output_iso/results/repack_decode.out 2026-09-29 15:09:00.871263055 -0400
# @@ -26,7 +26,7 @@
#
#  count
#  -----
# -    8
# +   12
#  (1 row)
#
#  injection_points_detach
not ok 10    - repack_decode                             302 ms
...
# 26 of 115 tests failed.

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2026-09-29%2014%3A01%3A15

Best regards,
Alexander
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    <div class="moz-cite-prefix">Hello Sawada-san,<br>
      <br>
      11.09.2026 20:56, Masahiko Sawada wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAD21AoBKZi3f5p3FYWehDQcWOoBszyedHgbXZMp-3F1h=K9hPQ@mail.gmail.com">
      <blockquote type="cite">
        <pre wrap="" class="moz-quote-pre">No objections here -- they look good to me too.  The isolation spec
addition is great, thanks.
</pre>
      </blockquote>
      <pre wrap="" class="moz-quote-pre">
Thank you for looking at the patches! Pushed.
</pre>
    </blockquote>
    <br>
    A recent failure of repack_decode.spec emitted by skink [1]:<br>
    # diff -U3
/home/bf/bf-build/skink-master/HEAD/pgsql/src/test/modules/injection_points/expected/repack_decode.out
/home/bf/bf-build/skink-master/HEAD/pgsql.build/testrun/injection_points/isolation/results/repack_decode.out<br>
    # ---
/home/bf/bf-build/skink-master/HEAD/pgsql/src/test/modules/injection_points/expected/repack_decode.out   
    2026-09-25 23:32:42.088355239 +0200<br>
    # +++
/home/bf/bf-build/skink-master/HEAD/pgsql.build/testrun/injection_points/isolation/results/repack_decode.out   
    2026-09-29 18:01:56.818281263 +0200<br>
    # @@ -26,7 +26,7 @@<br>
    #  <br>
    #  count<br>
    #  -----<br>
    # -    8<br>
    # +   12<br>
    #  (1 row)<br>
    #  <br>
    #  injection_points_detach<br>
    # 1 of 16 tests failed.<br>
    <br>
    apparently shows that the test is not immune to autovacuum.<br>
    <br>
    I can reproduce such failures locally with:<br>
    --- a/src/test/modules/injection_points/Makefile<br>
    +++ b/src/test/modules/injection_points/Makefile<br>
    @@ -21,3 +21,3 @@ ISOLATION = basic \<br>
                repack_commit_race \<br>
    -           repack_decode \<br>
    +           $(shell printf 'repack_decode %.0s' `seq 100`) \<br>
                repack_missingval \<br>
    <br>
    and<br>
    echo "autovacuum_naptime = 1" &gt;/tmp/temp.config<br>
    TEMP_CONFIG=/tmp/temp.config make -s check -C
    src/test/modules/injection_points/<br>
    ...<br>
    ok 9         - repack_decode                             272 ms<br>
    # diff -U3
    .../src/test/modules/injection_points/expected/repack_decode.out
.../src/test/modules/injection_points/output_iso/results/repack_decode.out<br>
    # ---
    .../src/test/modules/injection_points/expected/repack_decode.out   
    2026-09-29 14:51:55.810851901 -0400<br>
    # +++
.../src/test/modules/injection_points/output_iso/results/repack_decode.out 
    2026-09-29 15:09:00.871263055 -0400<br>
    # @@ -26,7 +26,7 @@<br>
    #  <br>
    #  count<br>
    #  -----<br>
    # -    8<br>
    # +   12<br>
    #  (1 row)<br>
    #  <br>
    #  injection_points_detach<br>
    not ok 10    - repack_decode                             302 ms<br>
    ...<br>
    # 26 of 115 tests failed.<br>
    <br>
    [1]
<a class="moz-txt-link-freetext" href="https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&amp;dt=2026-09-29%2014%3A01%3A15">https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&amp;dt=2026-09-29%2014%3A01%3A15</a><br>
    <br>
    Best regards,<br>
    Alexander<br>
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