Re: BUG #19687: ALTER SEQUENCE provokes error XX001 could not read blocks

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(at)postgresql(dot)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