0001-Fix-assertion-failure-when-decoding-synced-two-phase.patch

From ea5df7ebf90900e31e002317a3320cb66a8ef31a Mon Sep 17 00:00:00 2001
From: Zhijie Hou <houzj.fnst@cn.fujitsu.com>
Date: Thu, 17 Apr 2025 17:14:24 +0800
Subject: [PATCH] Fix assertion failure when decoding synced two-phase enabled
 slots.

Current, during slot synchronization, it skips updating the confirmed_lsn if it
detects that the catalog_xmin or restart_lsn of the synced slot has already
surpassed those of the remote slot on the primary. This behavior poses a
problem when two-phase commit is enabled on the remote slot. The lack of
synchronization between the latest confirmed_lsn and two_phase_at may result in
transactions prepared between the old confirmed_lsn and two_phase_at being
unexpectedly decoded and sent to subscribers following a promotion.

To fix this, we keep confirmed_flush updated even if the local catalog_xmin or
restart_lsn is more recent.
---
 src/backend/replication/logical/slotsync.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/backend/replication/logical/slotsync.c b/src/backend/replication/logical/slotsync.c
index e22d41891e6..2a12167cdaf 100644
--- a/src/backend/replication/logical/slotsync.c
+++ b/src/backend/replication/logical/slotsync.c
@@ -219,6 +219,21 @@ update_local_synced_slot(RemoteSlot *remote_slot, Oid remote_dbid,
 						  LSN_FORMAT_ARGS(slot->data.restart_lsn),
 						  slot->data.catalog_xmin));
 
+		/*
+		 * Keep confirmed_flush updated even if catalog_xmin or restart_lsn
+		 * advances beyond the values of the remote slot. This is necessary
+		 * when twophase is enabled on the remote slot, as failing to sync the
+		 * latest confirmed_lsn along with two_phase_at can lead to the
+		 * transactions between the old confirmed_lsn and two_phase_at being
+		 * unexpectedly decoded and sent to the subscriber.
+		 */
+		if (remote_slot->confirmed_lsn > remote_slot->restart_lsn)
+		{
+			SpinLockAcquire(&slot->mutex);
+			slot->data.confirmed_flush = remote_slot->confirmed_lsn;
+			SpinLockRelease(&slot->mutex);
+		}
+
 		if (remote_slot_precedes)
 			*remote_slot_precedes = true;
 	}
-- 
2.30.0.windows.2