Horton

Re: Conflict detection for update_deleted in logical replication

shveta malik <shveta.malik@gmail.com>

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From: shveta malik <shveta.malik@gmail.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, vignesh C <vignesh21@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, shveta malik <shveta.malik@gmail.com>
Date: 2025-06-11T09:34:03Z
Lists: pgsql-hackers 
On Tue, Jun 10, 2025 at 11:55 AM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> Here is the V35 patch set which includes the following changes:
>

Thank You for the patches, few comments:

1)
compute_min_nonremovable_xid:

+ /*
+ * Stop advancing xmin if an invalid non-removable transaction ID is
+ * found, otherwise update xmin.
+ */
+ if (!TransactionIdIsValid(nonremovable_xid))
+ *can_advance_xmin = false;

IMO, we can not have invalid nonremovable_xid here. It may be a
possibility in a later patch where we do stop-conflict-detection for a
worker and resets nonremovable_xid to Invalid. But in patch003, should
this rather be an Assert as we want to ensure that worker's oldest is
set to slot's-xmin by this time.

2)
postgres=# create subscription sub1  connection 'dbname=postgres
host=localhost user=shveta port=5433' publication pub1 WITH
(retain_conflict_info = true);
NOTICE:  deleted rows will continue to accumulate for detecting
conflicts until the subscription is enabled
NOTICE:  created replication slot "sub1" on publisher
CREATE SUBSCRIPTION

postgres=# alter subscription sub2 enable;
NOTICE:  deleted rows will continue to accumulate for detecting
conflicts until the subscription is enabled

We should not have this 'NOTICE:  deleted rows' in above 2 commands.


3)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;

Shall we enable regress_testsub as well before we drop it to catch
unexpected notices/warnings if any?


4)
postgres=# alter subscription sub2 disable;
WARNING:  commit timestamp and origin data required for detecting
conflicts won't be retained
HINT:  Consider setting "track_commit_timestamp" to true.

Do we need "track_commit_timestamp" related WARNING while disabling
rci sub as well? I feel it should be there while enabling it alone.

thanks
Shveta

Commits

  1. Fix intermittent BF failures in 035_conflicts.

  2. Resume conflict-relevant data retention automatically.

  3. Fix intermittent test failure introduced in 6456c6e2c4.

  4. Fix Coverity issue reported in commit a850be2fe.

  5. Add test to prevent premature removal of conflict-relevant data.

  6. Post-commit review fixes for 228c370868.

  7. Add max_retention_duration option to subscriptions.

  8. Detect and report update_deleted conflicts.

  9. Preserve conflict-relevant data during logical replication.

  10. Integrate FullTransactionIds deeper into two-phase code

  11. Improve checks for GUC recovery_target_timeline

  12. Prevent excessive delays before launching new logrep workers.

  13. Keep WAL segments by slot's last saved restart LSN

  14. Rework some code handling pg_subscription data in psql and pg_dump

  15. Use generateClonedIndexStmt to propagate CREATE INDEX to partitions.