From fb47544d0ca18312bf0b9e53e335217db5c41a08 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 14 Feb 2017 12:41:01 -0500
Subject: [PATCH] Minor fixes for WAL consistency checking.

Michael Paquier, reviewed and slightly revised by me.

Discussion: http://postgr.es/m/CAB7nPqRzCQb=vdfHvMtP0HMLBHU6z1aGdo4GJsUP-HP8jx+Pkw@mail.gmail.com
---
 src/backend/access/common/bufmask.c |  2 +-
 src/backend/access/heap/heapam.c    |  1 -
 src/backend/access/transam/xlog.c   | 12 +++++++++++-
 src/include/access/bufmask.h        |  2 +-
 4 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/backend/access/common/bufmask.c b/src/backend/access/common/bufmask.c
index 3b06115e03..10253d3354 100644
--- a/src/backend/access/common/bufmask.c
+++ b/src/backend/access/common/bufmask.c
@@ -5,7 +5,7 @@
  *	  in a page which can be different when the WAL is generated
  *	  and when the WAL is applied.
  *
- * Portions Copyright (c) 2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 2016-2017, PostgreSQL Global Development Group
  *
  * Contains common routines required for masking a page.
  *
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 0be48fb3ee..af258366a2 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -9167,7 +9167,6 @@ heap_mask(char *pagedata, BlockNumber blkno)
 
 		if (ItemIdIsNormal(iid))
 		{
-
 			HeapTupleHeader page_htup = (HeapTupleHeader) page_item;
 
 			/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 2dcff7f54b..f23e108628 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1360,6 +1360,16 @@ checkXLogConsistency(XLogReaderState *record)
 
 		Assert(XLogRecHasBlockImage(record, block_id));
 
+		if (XLogRecBlockImageApply(record, block_id))
+		{
+			/*
+			 * WAL record has already applied the page, so bypass the
+			 * consistency check as that would result in comparing the full
+			 * page stored in the record with itself.
+			 */
+			continue;
+		}
+
 		/*
 		 * Read the contents from the current buffer and store it in a
 		 * temporary page.
@@ -1390,7 +1400,7 @@ checkXLogConsistency(XLogReaderState *record)
 
 		/*
 		 * Read the contents from the backup copy, stored in WAL record and
-		 * store it in a temporary page. There is not need to allocate a new
+		 * store it in a temporary page. There is no need to allocate a new
 		 * page here, a local buffer is fine to hold its contents and a mask
 		 * can be directly applied on it.
 		 */
diff --git a/src/include/access/bufmask.h b/src/include/access/bufmask.h
index add2dc0cd1..722dfea8d8 100644
--- a/src/include/access/bufmask.h
+++ b/src/include/access/bufmask.h
@@ -7,7 +7,7 @@
  *	  individual rmgr, but we make things easier by providing some
  *	  common routines to handle cases which occur in multiple rmgrs.
  *
- * Portions Copyright (c) 2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 2016-2017, PostgreSQL Global Development Group
  *
  * src/include/access/bufmask.h
  *