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Message-ID: <7ac90032-cf60-4415-a7f9-cf512196db35@gmail.com>
Date: Wed, 23 Sep 2026 21:00:00 +0300
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User-Agent: Mozilla Thunderbird
Subject: Re: BUG #19687: ALTER SEQUENCE provokes error XX001 could not read
 blocks
To: Ayush Tiwari <ayushtiwari.slg01@gmail.com>,
 pgsql-bugs@lists.postgresql.org,
 Alexandre Felipe <o.alexandre.felipe@gmail.com>
References: <19687-dd094472b0c48afb@postgresql.org>
 <CAJTYsWWH0N-jJUviz3eviLa_ehGVsmumOmpTGufbRAsuDD2Uiw@mail.gmail.com>
Content-Language: en-US
From: Alexander Lakhin <exclusion@gmail.com>
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 <CAJTYsWWH0N-jJUviz3eviLa_ehGVsmumOmpTGufbRAsuDD2Uiw@mail.gmail.com>
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 <https://www.postgresql.org/message-id/7ac90032-cf60-4415-a7f9-cf512196db35%40gmail.com>
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Hello Ayush and Alexandre,

14.09.2026 22:07, Ayush Tiwari wrote:
> On Mon, 14 Sept 2026 at 20:23, PG Bug reporting form
> <noreply@postgresql.org> wrote:
>> The following bug has been logged on the website:
>>
>> Bug reference:      19687
>> ...
>> The following script:
>> ...
>>
>> triggers:
>> iteration 3
>> ERROR:  could not read blocks 0..0 in file "base/16384/16597": read only 0
>> of 8192 bytes
>> 2026-09-14 07:53:16.554 EEST [2078499:4] psql XX001 ERROR:  could not read
>> blocks 0..0 in file "base/16384/16597": read only 0 of 8192 bytes
>> 2026-09-14 07:53:16.554 EEST [2078499:5] psql XX001 STATEMENT:  SELECT *
>> FROM s;

Thank you for working on the fix!

Just for the record: with these parameters:
cpu_tuple_cost = 10000
min_parallel_table_scan_size = 1

set, the same script triggers also:
TRAP: failed Assert("RelFileLocatorEquals(relation->rd_locator, pscan->phs_locator)"), File: "tableam.c", Line: 173, 
PID: 4140896
ExceptionalCondition at assert.c:51:13
table_beginscan_parallel at tableam.c:178:14
ExecSeqScanInitializeWorker at nodeSeqscan.c:450:30
ExecParallelInitializeWorker at execParallel.c:1406:5
ParallelQueryMain at execParallel.c:1566:2
ParallelWorkerMain at parallel.c:1571:2
BackgroundWorkerMain at bgworker.c:868:2
postmaster_child_launch at launch_backend.c:269:3
StartBackgroundWorker at postmaster.c:4222:5
  (inlined by) maybe_start_bgworkers at postmaster.c:4385:9
ServerLoop at postmaster.c:1745:6
CreateOptsFile at postmaster.c:4166:3
  (inlined by) PostmasterMain at postmaster.c:1301:7
check_root at main.c:448:3
  (inlined by) main at main.c:195:3
...

Best regards,
Alexander
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    <div class="moz-cite-prefix">Hello Ayush and Alexandre,<br>
      <br>
      14.09.2026 22:07, Ayush Tiwari wrote:<span
      style="white-space: pre-wrap">
</span></div>
    <blockquote type="cite"
cite="mid:CAJTYsWWH0N-jJUviz3eviLa_ehGVsmumOmpTGufbRAsuDD2Uiw@mail.gmail.com">
      <pre wrap="" class="moz-quote-pre">On Mon, 14 Sept 2026 at 20:23, PG Bug reporting form
<a class="moz-txt-link-rfc2396E" href="mailto:noreply@postgresql.org">&lt;noreply@postgresql.org&gt;</a> wrote:
</pre>
      <blockquote type="cite">
        <pre wrap="" class="moz-quote-pre">The following bug has been logged on the website:

Bug reference:      19687
...
The following script:
...

triggers:
iteration 3
ERROR:  could not read blocks 0..0 in file "base/16384/16597": read only 0
of 8192 bytes
2026-09-14 07:53:16.554 EEST [2078499:4] psql XX001 ERROR:  could not read
blocks 0..0 in file "base/16384/16597": read only 0 of 8192 bytes
2026-09-14 07:53:16.554 EEST [2078499:5] psql XX001 STATEMENT:  SELECT *
FROM s;
</pre>
      </blockquote>
    </blockquote>
    <br>
    Thank you for working on the fix!<br>
    <br>
    Just for the record: with these parameters:<br>
    cpu_tuple_cost = 10000<br>
    min_parallel_table_scan_size = 1<br>
    <br>
    set, the same script triggers also:<br>
    TRAP: failed Assert("RelFileLocatorEquals(relation-&gt;rd_locator,
    pscan-&gt;phs_locator)"), File: "tableam.c", Line: 173, PID: 4140896<br>
    ExceptionalCondition at assert.c:51:13<br>
    table_beginscan_parallel at tableam.c:178:14<br>
    ExecSeqScanInitializeWorker at nodeSeqscan.c:450:30<br>
    ExecParallelInitializeWorker at execParallel.c:1406:5<br>
    ParallelQueryMain at execParallel.c:1566:2<br>
    ParallelWorkerMain at parallel.c:1571:2<br>
    BackgroundWorkerMain at bgworker.c:868:2<br>
    postmaster_child_launch at launch_backend.c:269:3<br>
    StartBackgroundWorker at postmaster.c:4222:5<br>
     (inlined by) maybe_start_bgworkers at postmaster.c:4385:9<br>
    ServerLoop at postmaster.c:1745:6<br>
    CreateOptsFile at postmaster.c:4166:3<br>
     (inlined by) PostmasterMain at postmaster.c:1301:7<br>
    check_root at main.c:448:3<br>
     (inlined by) main at main.c:195:3<br>
    ...<br>
    <br>
    Best regards,<br>
    Alexander<br>
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