Add code to apply some simple sanity checks to the header fields of a

page when it's read in, per pghackers discussion around 17-Feb.  Add a
GUC variable zero_damaged_pages that causes the response to be a WARNING
followed by zeroing the page, rather than the normal ERROR; this is per
Hiroshi's suggestion that there needs to be a way to get at the data
in the rest of the table.

1 files changed, 20 insertions, 1 deletions

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index a1abaf22c13..119cfe92b0d 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.134 2003/02/13 05:35:11 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.135 2003/03/28 20:17:13 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -49,6 +49,7 @@
 #include "miscadmin.h"
 #include "storage/buf_internals.h"
 #include "storage/bufmgr.h"
+#include "storage/bufpage.h"
 #include "storage/proc.h"
 #include "storage/smgr.h"
 #include "utils/relcache.h"
@@ -59,6 +60,10 @@
 	(*((XLogRecPtr*) MAKE_PTR((bufHdr)->data)))
 
 
+/* GUC variable */
+bool	zero_damaged_pages = false;
+
+
 static void WaitIO(BufferDesc *buf);
 static void StartBufferIO(BufferDesc *buf, bool forInput);
 static void TerminateBufferIO(BufferDesc *buf);
@@ -217,6 +222,20 @@ ReadBufferInternal(Relation reln, BlockNumber blockNum,
 	{
 		status = smgrread(DEFAULT_SMGR, reln, blockNum,
 						  (char *) MAKE_PTR(bufHdr->data));
+		/* check for garbage data */
+		if (status == SM_SUCCESS &&
+			!PageHeaderIsValid((PageHeader) MAKE_PTR(bufHdr->data)))
+		{
+			if (zero_damaged_pages)
+			{
+				elog(WARNING, "Invalid page header in block %u of %s; zeroing out page",
+					 blockNum, RelationGetRelationName(reln));
+				MemSet((char *) MAKE_PTR(bufHdr->data), 0, BLCKSZ);
+			}
+			else
+				elog(ERROR, "Invalid page header in block %u of %s",
+					 blockNum, RelationGetRelationName(reln));
+		}
 	}
 
 	if (isLocalBuf)