Re: Logical Replication of sequences

Peter Smith <smithpb2250@gmail.com>

From: Peter Smith <smithpb2250@gmail.com>

To: vignesh C <vignesh21@gmail.com>

Cc: Shlok Kyal <shlok.kyal.oss@gmail.com>, Chao Li <li.evan.chao@gmail.com>, shveta malik <shveta.malik@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Shinya Kato <shinya11.kato@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Dilip Kumar <dilipbalaut@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Euler Taveira <euler@eulerto.com>, Michael Paquier <michael@paquier.xyz>, "Jonathan S. Katz" <jkatz@postgresql.org>

Date: 2025-12-19T04:35:30Z

Lists: pgsql-hackers

Commits

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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

Hi Vignesh.

I had a quick look at this patch.

======

- * Instead, we invalidate only the relsyncache.
+ * Instead, invalidate the relation sync cache for publications that
+ * include tables. Invalidation is not required for sequences only
+ * publications.
  */
- InvalidatePubRelSyncCache(pub->oid, pub->puballtables);
+ if (!pub->puballsequences || pub->puballtables)
+ InvalidatePubRelSyncCache(pub->oid, pub->puballtables);

I felt all these "sequence only" conditions are becoming difficult to read.

It wonder if it would be better to introduce some function like:

bool
PubHasSequencesOnly(pub)
{
  return pub->puballsequences && !pub->puballtables;
}

IIUC the current patch code only works because publication syntax like
below is not yet supported:

CREATE PUBLICATION pub1 FOR ALL SEQUENCES, TABLE t1;

But when that syntax does become possible, then all these conditions
will be broken.

Should we prepare for that eventuality by introducing some function
right now, so as to contain all the future broken code?

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