Re: Logical Replication of sequences

Hi Vignesh.

After applying the v20240703-0003 patch, I was always getting errors
when running the subscription TAP tests.

# +++ tap check in src/test/subscription +++
t/001_rep_changes.pl ............... ok
t/002_types.pl ..................... ok
t/003_constraints.pl ............... ok
t/004_sync.pl ...................... ok
t/005_encoding.pl .................. ok
t/006_rewrite.pl ................... ok
t/007_ddl.pl ....................... 3/?
#   Failed test 'Alter subscription set publication throws warning for
non-existent publication'
#   at t/007_ddl.pl line 67.
Bailout called.  Further testing stopped:  pg_ctl stop failed
# Tests were run but no plan was declared and done_testing() was not seen.
FAILED--Further testing stopped: pg_ctl stop failed
make: *** [check] Error 255

~~~

The publisher log shows an Assert TRAP occurred:

2024-07-04 18:15:40.089 AEST [745] mysub1 LOG:  statement: SELECT
DISTINCT s.schemaname, s.sequencename
  FROM pg_catalog.pg_publication_sequences s
WHERE s.pubname IN ('mypub', 'non_existent_pub', 'non_existent_pub1',
'non_existent_pub2')
TRAP: failed Assert("IsA(list, OidList)"), File:
"../../../src/include/nodes/pg_list.h", Line: 323, PID: 745

~~~

A debugging backtrace looks like below:

Core was generated by `postgres: publisher: walsender postgres
postgres [local] SELECT               '.
Program terminated with signal 6, Aborted.
#0  0x00007f36f44f02c7 in raise () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install
glibc-2.17-260.el7_6.6.x86_64 pcre-8.32-17.el7.x86_64
(gdb) bt
#0  0x00007f36f44f02c7 in raise () from /lib64/libc.so.6
#1  0x00007f36f44f19b8 in abort () from /lib64/libc.so.6
#2  0x0000000000bb8be1 in ExceptionalCondition (conditionName=0xc7aa6c
"IsA(list, OidList)",
    fileName=0xc7aa10 "../../../src/include/nodes/pg_list.h",
lineNumber=323) at assert.c:66
#3  0x00000000005f2c57 in list_nth_oid (list=0x27948f0, n=0) at
../../../src/include/nodes/pg_list.h:323
#4  0x00000000005f5491 in pg_get_publication_sequences
(fcinfo=0x2796a00) at pg_publication.c:1334
#5  0x0000000000763d10 in ExecMakeTableFunctionResult
(setexpr=0x27b2fd8, econtext=0x27b2ef8, argContext=0x2796900,
...

Something goes wrong indexing into that 'sequences' list.

1329 funcctx = SRF_PERCALL_SETUP();
1330 sequences = (List *) funcctx->user_fctx;
1331
1332 if (funcctx->call_cntr < list_length(sequences))
1333 {
1334 Oid relid = list_nth_oid(sequences, funcctx->call_cntr);
1335
1336 SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(relid));
1337 }

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Perhaps now it is time to create a CF entry for this thread because
the cfbot could have detected the error earlier.

======
Kind Regards,
Peter Smith.
Fujitsu Australia