Index: src/backend/catalog/index.c
===================================================================
RCS file: /home/projects/pgsql/cvsroot/pgsql/src/backend/catalog/index.c,v
retrieving revision 1.144
diff -c -r1.144 index.c
*** src/backend/catalog/index.c	2001/03/22 06:16:10	1.144
--- src/backend/catalog/index.c	2001/03/30 22:55:54
***************
*** 864,869 ****
--- 864,876 ----
  		indexInfo->ii_NumKeyAttrs < 1)
  		elog(ERROR, "must index at least one attribute");
  
+ 	if (heapRelationName && !allow_system_table_mods &&
+ 		IsSystemRelationName(heapRelationName) && IsNormalProcessingMode())
+ 	{
+ 		elog(ERROR, "You can not create indexes on system tables:  '%s'",
+ 			 heapRelationName);
+ 	}
+ 
  	/*
  	 * get heap relation oid and open the heap relation
  	 */