0001-Exit-walsender-before-confirming-remote-flush-in-log.patch

From cc444e339af93bf4a27ac644f5d65b0466b65126 Mon Sep 17 00:00:00 2001
From: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Date: Thu, 22 Dec 2022 02:49:48 +0000
Subject: [PATCH] Exit walsender before confirming remote flush in logical
 replication

---
 src/backend/replication/walsender.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index c11bb3716f..08d4a9861f 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -3099,8 +3099,9 @@ XLogSendLogical(void)
  * NB: This should only be called when the shutdown signal has been received
  * from postmaster.
  *
- * Note that if we determine that there's still more data to send, this
- * function will return control to the caller.
+ * Note that if we determine that there's still more data to send or we are in
+ * the physical replication more, this function will return control to the
+ * caller.
  */
 static void
 WalSndDone(WalSndSendDataCallback send_data)
@@ -3118,8 +3119,17 @@ WalSndDone(WalSndSendDataCallback send_data)
 	replicatedPtr = XLogRecPtrIsInvalid(MyWalSnd->flush) ?
 		MyWalSnd->write : MyWalSnd->flush;
 
-	if (WalSndCaughtUp && sentPtr == replicatedPtr &&
-		!pq_is_send_pending())
+	/*
+	 * Exit if we are in the convenient time.
+	 *
+	 * Note that in case of logical replication, we don't have to wait that all
+	 * sent data to be flushed on the subscriber. It will request to send WALs
+	 * from the last received point, and we cannot support clean switchover in
+	 * logical replication.
+	 */
+	if (WalSndCaughtUp &&
+		(send_data == XLogSendLogical ||
+		 (sentPtr == replicatedPtr && !pq_is_send_pending())))
 	{
 		QueryCompletion qc;
 
-- 
2.27.0