Horton

RE: Logical Replication of sequences

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'vignesh C' <vignesh21@gmail.com>, shveta malik <shveta.malik@gmail.com>
Cc: Nisha Moond <nisha.moond412@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Masahiko Sawada <sawada.mshk@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>
Date: 2025-08-15T11:16:30Z
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

Dear Vignesh,

Thanks for updating the patch. Here are my small comments:

01.
Per pgindent report, publicationcmds.c should be fixed.

02.
```
+       ScanKeyInit(&skey[1],
+                               Anum_pg_subscription_rel_srsubstate,
+                               BTEqualStrategyNumber, F_CHARNE,
+                               CharGetDatum(SUBREL_STATE_READY));
```

I felt it is more natural to "srsubstate = 'i'", instead of "srsubstate <> 'r'"

03.
```
+               table_close(sequence_rel, NoLock);
+       }
+
+       /* Cleanup */
+       systable_endscan(scan);
+       table_close(rel, AccessShareLock);
+
+       CommitTransactionCommand();
```

To clarify, can we release the sequence at the end of the inner loop?

I found that sequence relation is closed (but not release the lock) then commit
the transaction once. This approach cannot avoid dropping it by concurrent
transactions, but maybe you did due to the performance reason. So...I felt we
may able to release bit earlier.

04.
```
+                       sequence_rel = try_table_open(seqinfo->localrelid, RowExclusiveLock);
+
+                       /* Get the local sequence */
+                       tup = SearchSysCache1(SEQRELID, ObjectIdGetDatum(seqinfo->localrelid));
+                       if (!sequence_rel || !HeapTupleIsValid(tup))
+                       {
+                               elog(LOG, "skip synchronization of sequence \"%s.%s\" because it has been dropped concurrently",
+                                        seqinfo->nspname, seqinfo->seqname);
+
+                               batch_skipped_count++;
+                               continue;
+                       }
```

a. Code comment can be atop try_table_open().
b. Isn't it enough to check HeapTupleIsValid() here?

05.
```
+                       /* Update the sequence only if the parameters are identical */
+                       if (seqform->seqtypid == seqtypid &&
+                               seqform->seqmin == seqmin && seqform->seqmax == seqmax &&
+                               seqform->seqcycle == seqcycle &&
+                               seqform->seqstart == seqstart &&
+                               seqform->seqincrement == seqincrement)
```

I noticed that seqcache is not compared. Is there a reason?

06.
```
+       foreach_ptr(LogicalRepSequenceInfo, seq_info, sequences_to_copy)
+       {
+               pfree(seq_info->seqname);
+               pfree(seq_info->nspname);
+               pfree(seq_info);
+       }
```

Per comment atop foreach_delete_current(), we should not directly do pfree()
the entry. Can you use foreach_delete_current()? I.e.,

07.
```
	foreach_ptr(LogicalRepSequenceInfo, seq_info, sequences_to_copy)
	{
		pfree(seq_info->seqname);
		pfree(seq_info->nspname);
		
		sequences_to_copy =
			foreach_delete_current(sequences_to_copy, seq_info);
	}
```

08.
```
+$node_subscriber->init(allows_streaming => 'logical');
```

Actually no need to set to 'logical'.


Best regards,
Hayato Kuroda
FUJITSU LIMITED