Horton

Re: Logical Replication of sequences

Nisha Moond <nisha.moond412@gmail.com>

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From: Nisha Moond <nisha.moond412@gmail.com>
To: vignesh C <vignesh21@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Masahiko Sawada <sawada.mshk@gmail.com>, shveta malik <shveta.malik@gmail.com>, Shlok Kyal <shlok.kyal.oss@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Euler Taveira <euler@eulerto.com>, Michael Paquier <michael@paquier.xyz>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, "Jonathan S. Katz" <jkatz@postgresql.org>
Date: 2025-05-14T04:25:42Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Doc: Add documentation for sequence synchronization.

  2. Remove unused assignment in CREATE PUBLICATION grammar.

  3. Add seq_sync_error_count to subscription statistics.

  4. Fix few issues in commit 5509055d69.

  5. Add sequence synchronization for logical replication.

  6. Add worker type argument to logical replication worker functions.

  7. Introduce "REFRESH SEQUENCES" for subscriptions.

  8. Refactor logical worker synchronization code into a separate file.

  9. Standardize use of REFRESH PUBLICATION in code and messages.

  10. Add "ALL SEQUENCES" support to publications.

  11. Expose sequence page LSN via pg_get_sequence_data.

  12. Resume conflict-relevant data retention automatically.

  13. Post-commit review fixes for 228c370868.

  14. Generate GUC tables from .dat file

On Sat, May 3, 2025 at 7:28 PM vignesh C <vignesh21@gmail.com> wrote:
>
>
> There was one pending open comment #6 from [1]. This has been
> addressed in the attached patch.

Thank you for the patches, here are my comments for patch-004: sequencesync.c

copy_sequences()
-------------------
1)
+ if (first)
+ first = false;
+ else
+ appendStringInfoString(seqstr, ", ");

We can avoid additional variable here, suggestion -
if (seqstr->len > 0)
  appendStringInfoString(seqstr, ", ");
~~~~

2)
+ else
+ {
+ *sequence_sync_error = true;
+ append_mismatched_sequences(mismatched_seqs, seqinfo);
+ }

I think *sequence_sync_error = true can be removed from here, as we
can avoid setting it for every mismatch, as it is already set at the
end of the function if any sequence mismatches are found.
~~~~

3)
+ if (message_level_is_interesting(DEBUG1))
+ {
+ /* LOG all the sequences synchronized during current batch. */
+ for (int i = 0; i < curr_batch_seq_count; i++)
+ {
+ LogicalRepSequenceInfo *done_seq;
...
+
+ ereport(DEBUG1,
+ errmsg_internal("logical replication synchronization for
subscription \"%s\", sequence \"%s\" has finished",
+ get_subscription_name(subid, false),
+ done_seq->seqname));
+ }
+ }

3a) I think the DEBUG1 log can be moved inside the while loop just
above, to avoid traversing the list again unnecessarily.
~~~~

LogicalRepSyncSequences():
-----------------------------
4)
+ /*
+ * Sequence synchronization failed due to a parameter mismatch. Set the
+ * failure time to prevent immediate initiation of the sequencesync
+ * worker.
+ */
+ if (sequence_sync_error)
+ {
+ logicalrep_seqsyncworker_set_failuretime();
+ ereport(LOG,
+ errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("sequence synchronization failed because the parameters
between the publisher and subscriber do not match for all
sequences"));
+ }

I think saying "sequence synchronization failed" could be misleading,
as the matched sequences will still be synced successfully. It might
be clearer to reword it to something like:
"sequence synchronization failed for some sequences because the
parameters between the publisher and subscriber do not match."
~~~~

--
Thanks,
Nisha