Re: Logical Replication of sequences
Peter Smith <smithpb2250@gmail.com>
From: Peter Smith <smithpb2250@gmail.com>
To: vignesh C <vignesh21@gmail.com>
Cc: "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: 2025-04-24T06:06:49Z
Lists: pgsql-hackers
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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
Hi Vignesh,
Some comments for v20250422-0004.
======
src/backend/commands/sequence.c
pg_sequence_state:
1.
+ * The page_lsn will be utilized in logical replication sequence
+ * synchronization to record the page_lsn of sequence in the
pg_subscription_rel
+ * system catalog. It will reflect the page_lsn of the remote sequence at the
+ * moment it was synchronized.
+ *
SUGGESTION (minor rewording)
The page LSN will be used in logical replication of sequences to
record the LSN of the sequence page in the pg_subscription_rel system
catalog. It reflects the LSN of the remote sequence at the time it
was synchronized.
======
src/backend/commands/subscriptioncmds.c
AlterSubscription:
2.
- case ALTER_SUBSCRIPTION_REFRESH:
+ case ALTER_SUBSCRIPTION_REFRESH_PUBLICATION_SEQUENCES:
+ {
+ if (!sub->enabled)
+ ereport(ERROR,
+ errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("ALTER SUBSCRIPTION ... REFRESH PUBLICATION SEQUENCES is not
allowed for disabled subscriptions"));
+
+ PreventInTransactionBlock(isTopLevel, "ALTER SUBSCRIPTION ...
REFRESH PUBLICATION SEQUENCES");
+
+ AlterSubscription_refresh(sub, true, NULL, false, true, true);
+
+ break;
+ }
+
+ case ALTER_SUBSCRIPTION_REFRESH_PUBLICATION:
I felt these should be reordered so REFRESH PUBLICATION comes before
REFRESH PUBLICATION SEQUENCES. No particular reason, but AFAICT that
is how you've ordered them in all other places -- eg, gram.y, the
documentation, etc. -- so let's be consistent.
======
src/backend/replication/logical/launcher.c
3.
+/*
+ * Update the failure time of the sequencesync worker in the subscription's
+ * apply worker.
+ *
+ * This function is invoked when the sequencesync worker exits due to a
+ * failure.
+ */
+void
+logicalrep_seqsyncworker_failuretime(int code, Datum arg)
It might be better to call this function name
'logicalrep_seqsyncworker_failure' (not _failuretime) because it is
more generic, and in future, you might want to do more things in this
function apart from just setting the failure time.
======
src/backend/replication/logical/syncutils.c
SyncFinishWorker:
4.
+ /* This is a clean exit, so no need to set a sequence failure time. */
+ if (wtype == WORKERTYPE_SEQUENCESYNC)
+ cancel_before_shmem_exit(logicalrep_seqsyncworker_failuretime, 0);
+
I didn't think the comment should mention setting 'failure time'.
Those details belong at a lower level -- here, it is better to be more
generic.
SUGGESTION:
/* This is a clean exit, so no need for any sequence failure logic. */
======
Kind Regards,
Peter Smith.
Fujitsu Australia