Force zero_damaged_pages to be effectively ON during recovery from WAL,

since there is no need to worry about damaged pages when we are going to
overwrite them anyway from the WAL.  Per recent discussion.

Author: tglsfdc

src/backend/storage/buffer/bufmgr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.147 2003/11/29 19:51:56 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.148 2003/12/01 16:53:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -231,7 +231,13 @@ ReadBufferInternal(Relation reln, BlockNumber blockNum,
 		if (status == SM_SUCCESS &&
 			!PageHeaderIsValid((PageHeader) MAKE_PTR(bufHdr->data)))
 		{
-			if (zero_damaged_pages)
+			/*
+			 * During WAL recovery, the first access to any data page should
+			 * overwrite the whole page from the WAL; so a clobbered page
+			 * header is not reason to fail.  Hence, when InRecovery we may
+			 * always act as though zero_damaged_pages is ON.
+			 */
+			if (zero_damaged_pages || InRecovery)
 			{
 				ereport(WARNING,
 						(errcode(ERRCODE_DATA_CORRUPTED),