0001-Mark-freed-overflow-page-as-UNUSED-pagetype-v2.patch

From 86eb711ea80b495c9d2f5228558682d0e95c41eb Mon Sep 17 00:00:00 2001
From: ashu <ashu@localhost.localdomain>
Date: Thu, 23 Mar 2017 16:47:17 +0530
Subject: [PATCH] Mark freed overflow page as UNUSED pagetype v2

---
 src/backend/access/hash/hash_xlog.c |  9 +++++++++
 src/backend/access/hash/hashovfl.c  | 13 ++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/hash/hash_xlog.c b/src/backend/access/hash/hash_xlog.c
index d9ac42c..2ccaf46 100644
--- a/src/backend/access/hash/hash_xlog.c
+++ b/src/backend/access/hash/hash_xlog.c
@@ -697,11 +697,20 @@ hash_xlog_squeeze_page(XLogReaderState *record)
 	if (XLogReadBufferForRedo(record, 2, &ovflbuf) == BLK_NEEDS_REDO)
 	{
 		Page		ovflpage;
+		HashPageOpaque ovflopaque;
 
 		ovflpage = BufferGetPage(ovflbuf);
 
 		_hash_pageinit(ovflpage, BufferGetPageSize(ovflbuf));
 
+		ovflopaque = (HashPageOpaque) PageGetSpecialPointer(ovflpage);
+
+		ovflopaque->hasho_prevblkno = InvalidBlockNumber;
+		ovflopaque->hasho_nextblkno = InvalidBlockNumber;
+		ovflopaque->hasho_bucket = -1;
+		ovflopaque->hasho_flag = LH_UNUSED_PAGE;
+		ovflopaque->hasho_page_id = HASHO_PAGE_ID;
+
 		PageSetLSN(ovflpage, lsn);
 		MarkBufferDirty(ovflbuf);
 	}
diff --git a/src/backend/access/hash/hashovfl.c b/src/backend/access/hash/hashovfl.c
index a3cae21..d3eaee0 100644
--- a/src/backend/access/hash/hashovfl.c
+++ b/src/backend/access/hash/hashovfl.c
@@ -591,9 +591,20 @@ _hash_freeovflpage(Relation rel, Buffer bucketbuf, Buffer ovflbuf,
 	/*
 	 * Initialize the freed overflow page.  Just zeroing the page won't work,
 	 * because WAL replay routines expect pages to be initialized. See
-	 * explanation of RBM_NORMAL mode atop XLogReadBufferExtended.
+	 * explanation of RBM_NORMAL mode atop XLogReadBufferExtended. Also, mark
+	 * the page as UNUSED type and retain it's page id. This allows the tools
+	 * like pageinspect to consider it as a hash page.
 	 */
 	_hash_pageinit(ovflpage, BufferGetPageSize(ovflbuf));
+
+	ovflopaque = (HashPageOpaque) PageGetSpecialPointer(ovflpage);
+
+	ovflopaque->hasho_prevblkno = InvalidBlockNumber;
+	ovflopaque->hasho_nextblkno = InvalidBlockNumber;
+	ovflopaque->hasho_bucket = -1;
+	ovflopaque->hasho_flag = LH_UNUSED_PAGE;
+	ovflopaque->hasho_page_id = HASHO_PAGE_ID;
+
 	MarkBufferDirty(ovflbuf);
 
 	if (BufferIsValid(prevbuf))
-- 
1.8.3.1