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.

src/backend/utils/misc/guc.c

@@ -5,7 +5,7 @@
  * command, configuration file, and command line options.
  * See src/backend/utils/misc/README for more information.
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.117 2003/03/20 04:51:44 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.118 2003/03/28 20:17:13 tgl Exp $
  *
  * Copyright 2000 by PostgreSQL Global Development Group
  * Written by Peter Eisentraut <peter_e@gmx.net>.
@@ -357,6 +357,10 @@ static struct config_bool
 		{"fsync", PGC_SIGHUP}, &enableFsync,
 		true, NULL, NULL
 	},
+	{
+		{"zero_damaged_pages", PGC_SUSET}, &zero_damaged_pages,
+		false, NULL, NULL
+	},
 	{
 		{"silent_mode", PGC_POSTMASTER}, &SilentMode,
 		false, NULL, NULL

src/backend/utils/misc/postgresql.conf.sample

@@ -213,6 +213,6 @@
 #sql_inheritance = true
 #transform_null_equals = false
 #statement_timeout = 0		# 0 is disabled, in milliseconds
+#zero_damaged_pages = false     # set this true only for disaster recovery
 #db_user_namespace = false
 #preload_libraries = ''
-