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help / color / mirror / Atom feedFrom: Álvaro Herrera <alvherre@kurilemu.de>
Subject: [PATCH] Remove stale XXX comment in logical launcher
Date: Tue, 8 Sep 2026 09:44:36 +0200
An XXX comment in launcher.c questioned why the slot drop does not request
disabling logical decoding. But the conflict detection slot is a physical slot,
so there is no logical decoding state to disable. Remove the comment and add an
explanation atop the slot creation function clarifying that the slot is physical.
Author: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Reviewed-by: shveta malik <shveta.malik@gmail.com>
Discussion: https://postgr.es/m/TY4PR01MB177186C8AB596F30DF704ECDC94B62@TY4PR01MB17718.jpnprd01.prod.outlook.com
---
src/backend/replication/logical/launcher.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index c328ad53ecc..5057a928adb 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -1284,12 +1284,12 @@ ApplyLauncherMain(Datum main_arg)
retain_dead_tuples = true;
/*
- * Create a replication slot to retain information necessary
- * for conflict detection such as dead tuples, commit
- * timestamps, and origins.
+ * Create a (physical) replication slot to retain information
+ * necessary for conflict detection such as dead tuples,
+ * commit timestamps, and origins.
*
* The slot is created before starting the apply worker to
- * prevent it from unnecessarily maintaining its
+ * prevent the worker from unnecessarily maintaining its
* oldest_nonremovable_xid.
*
* The slot is created even for a disabled subscription to
@@ -1418,7 +1418,6 @@ ApplyLauncherMain(Datum main_arg)
if (MyReplicationSlot)
{
if (!retain_dead_tuples)
- /* XXX unclear why we don't request logical decoding disable */
ReplicationSlotDropAcquired(false);
else if (can_update_xmin)
update_conflict_slot_xmin(xmin);
@@ -1627,6 +1626,11 @@ reset_conflict_slot_xmin_to_safe_horizon(void)
/*
* Create and acquire the replication slot used to retain information for
* conflict detection, if not yet.
+ *
+ * A physical slot is enough, as no logical decoding is going to be performed
+ * through it. In fact, the slot will only be used through its xmin horizon
+ * to prevent the removal of dead tuples and commit timestamp data required by
+ * subscriptions with retain_dead_tuples enabled in any database.
*/
void
CreateConflictDetectionSlot(void)
--
2.47.3
--3lvjw6xwjq6anblz--
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Subject: Re: [PATCH] Remove stale XXX comment in logical launcher
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