commit 544e2b1661413fe08e3083f03063c12c0d7cf3aa
Author: Ian Barwick <ian@2ndquadrant.com>
Date:   Tue Sep 8 12:24:14 2020 +0900

    Fix snapshot caching on standbys

    Addresses issue introduced in 623a9ba.

diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index b8bedca04a..227d03bbce 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3320,6 +3320,14 @@ multixact_redo(XLogReaderState *record)
 	}
 	else
 		elog(PANIC, "multixact_redo: unknown op code %u", info);
+
+	/*
+	 * Advance xactCompletionCount so rebuilds of snapshot contents
+	 * can be triggered.
+	 */
+	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+	ShmemVariableCache->xactCompletionCount++;
+	LWLockRelease(ProcArrayLock);
 }

 Datum
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index af6afcebb1..04ca858918 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -5915,6 +5915,14 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	 */
 	if (XactCompletionApplyFeedback(parsed->xinfo))
 		XLogRequestWalReceiverReply();
+
+	/*
+	 * Advance xactCompletionCount so rebuilds of snapshot contents
+	 * can be triggered.
+	 */
+	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+	ShmemVariableCache->xactCompletionCount++;
+	LWLockRelease(ProcArrayLock);
 }

 /*
@@ -5978,6 +5986,14 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)

 	/* Make sure files supposed to be dropped are dropped */
 	DropRelationFiles(parsed->xnodes, parsed->nrels, true);
+
+	/*
+	 * Advance xactCompletionCount so rebuilds of snapshot contents
+	 * can be triggered.
+	 */
+	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+	ShmemVariableCache->xactCompletionCount++;
+	LWLockRelease(ProcArrayLock);
 }

 void