Re: Logical Replication of sequences

shveta malik <shveta.malik@gmail.com>

From: shveta malik <shveta.malik@gmail.com>

To: vignesh C <vignesh21@gmail.com>

Cc: Masahiko Sawada <sawada.mshk@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Nisha Moond <nisha.moond412@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Shlok Kyal <shlok.kyal.oss@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>, shveta malik <shveta.malik@gmail.com>

Date: 2025-08-26T05:51:05Z

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 →

Doc: Add documentation for sequence synchronization.
- 55cefadde874 19 (unreleased) landed
Remove unused assignment in CREATE PUBLICATION grammar.
- bfb7419b0bbe 19 (unreleased) landed
Add seq_sync_error_count to subscription statistics.
- f6a4c498dcf6 19 (unreleased) landed
Fix few issues in commit 5509055d69.
- 5a4eba558aa7 19 (unreleased) landed
Add sequence synchronization for logical replication.
- 5509055d6956 19 (unreleased) landed
Add worker type argument to logical replication worker functions.
- 3e8e05596a02 19 (unreleased) landed
Introduce "REFRESH SEQUENCES" for subscriptions.
- f0b3573c3aac 19 (unreleased) landed
Refactor logical worker synchronization code into a separate file.
- 41c674d2e31e 19 (unreleased) landed
Standardize use of REFRESH PUBLICATION in code and messages.
- 2436b8c047ff 19 (unreleased) landed
Add "ALL SEQUENCES" support to publications.
- 96b378497346 19 (unreleased) landed
Expose sequence page LSN via pg_get_sequence_data.
- b93172ca59f4 19 (unreleased) landed
Resume conflict-relevant data retention automatically.
- 0d48d393d465 19 (unreleased) cited
Post-commit review fixes for 228c370868.
- 1f7e9ba3ac4e 19 (unreleased) cited
Generate GUC tables from .dat file
- 63599896545c 19 (unreleased) cited

On Thu, Aug 21, 2025 at 10:08 PM vignesh C <vignesh21@gmail.com> wrote:
>

> I have also addressed all the comments from [1] in the attached
> v20250823 version patch.
> [1] - https://www.postgresql.org/message-id/CAA4eK1%2BoVQW8oP%3DLo1X8qac6dzg-fgGQ6R_F_psfokUEqe%2Ba6w%40mail.gmail.com
>

Thank You for the patches. I see a race condition between alter-seq and refresh.

Say we have triggered REFRESH on sub, and when seq-sync worker is in
copy_sequences() where it has retrieved the local sequence using
seqname while it has not locked the sequence-relation yet, if
meanwhile we alter sequence and change its name, seq-sync worker ends
up syncing that renamed sequence values with old-fetched sequence.
Steps:

1) create a sequence seq0 on pub and sub
2) do REFRESH PUBLICATION SEQ on sub
3) In seq-sync worker, during copy_sequences() hold debugger at:
seqinfo->remote_seq_fetched = true;
4) rename sequence on sub :  ALTER SEQUENCE seq0 RENAME TO seq1;
5) release debugger in seq-sync worker. It will end up syncing seq1
using seq0 fetched from pub.

thanks
Shveta