Horton

RE: Conflict detection for update_deleted in logical replication

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

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, vignesh C <vignesh21@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, shveta malik <shveta.malik@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-04-15T08:52:03Z
Lists: pgsql-hackers 
Dear Hou,

Thanks for updating the patch! I can finally come back to the thread.

Regarding the max_retain_conflict_duration, I prefer GUC approach because it has
already had a mechanism for converting unit: subscription option does not have it.

Below part contains my comments:

01. check_new_cluster_subscription_configuration

```
@@ -2024,6 +2025,7 @@ check_new_cluster_subscription_configuration(void)
        PGresult   *res;
        PGconn     *conn;
        int                     max_active_replication_origins;
+       int                     max_replication_slots;
```

I feel max_replication_slots is needed when old_cluster.sub_retain_conflict_info is true.

02. check_old_cluster_for_valid_slots
```
+                       /*
+                        * The name "pg_conflict_detection" (defined as
+                        * CONFLICT_DETECTION_SLOT) has been reserved for logical
+                        * replication conflict detection since PG18.
+                        */
+                       if (GET_MAJOR_VERSION(new_cluster.major_version) >= 1800 &&
+                               strcmp(slot->slotname, "pg_conflict_detection") == 0)
```

IIUC, we can assume that the vesion of new_cluster is same as pg_upgrade, so no
need to check the major version here.

03.

Can we add a test for upgrading subscriber node with retain_conflict_info in 004_subscription?

Best regards,
Hayato Kuroda
FUJITSU LIMITED

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.