hash: Support WAL consistency checking.

Kuntal Ghosh, reviewed by Amit Kapila and Ashutosh Sharma, with
a few tweaks by me.

Discussion: http://postgr.es/m/CAGz5QCJLERUn_zoO0eDv6_Y_d0o4tNTMPeR7ivTLBg4rUrJdwg@mail.gmail.com

1 files changed, 36 insertions, 0 deletions

diff --git a/src/backend/access/hash/hash_xlog.c b/src/backend/access/hash/hash_xlog.c
index d435215259b..0c830ab5952 100644
--- a/src/backend/access/hash/hash_xlog.c
+++ b/src/backend/access/hash/hash_xlog.c
@@ -14,6 +14,7 @@
  */
 #include "postgres.h"
 
+#include "access/bufmask.h"
 #include "access/hash.h"
 #include "access/hash_xlog.h"
 #include "access/xlogutils.h"
@@ -961,3 +962,38 @@ hash_redo(XLogReaderState *record)
 			elog(PANIC, "hash_redo: unknown op code %u", info);
 	}
 }
+
+/*
+ * Mask a hash page before performing consistency checks on it.
+ */
+void
+hash_mask(char *pagedata, BlockNumber blkno)
+{
+	Page		page = (Page) pagedata;
+	HashPageOpaque opaque;
+
+	mask_page_lsn(page);
+
+	mask_page_hint_bits(page);
+	mask_unused_space(page);
+
+	opaque = (HashPageOpaque) PageGetSpecialPointer(page);
+
+	if (opaque->hasho_flag & LH_UNUSED_PAGE)
+	{
+		/*
+		 * Mask everything on a UNUSED page.
+		 */
+		mask_page_content(page);
+	}
+	else if ((opaque->hasho_flag & LH_BUCKET_PAGE) ||
+			 (opaque->hasho_flag & LH_OVERFLOW_PAGE))
+	{
+		/*
+		 * In hash bucket and overflow pages, it is possible to modify the
+		 * LP_FLAGS without emitting any WAL record. Hence, mask the line
+		 * pointer flags. See hashgettuple() for details.
+		 */
+		mask_lp_flags(page);
+	}
+}