Repair some REINDEX problems per recent discussions. The relcache is

now able to cope with assigning new relfilenode values to nailed-in-cache
indexes, so they can be reindexed using the fully crash-safe method.  This
leaves only shared system indexes as special cases.  Remove the 'index
deactivation' code, since it provides no useful protection in the shared-
index case.  Require reindexing of shared indexes to be done in standalone
mode, but remove other restrictions on REINDEX.  -P (IgnoreSystemIndexes)
now prevents using indexes for lookups, but does not disable index updates.
It is therefore safe to allow from PGOPTIONS.  Upshot: reindexing system catalogs
can be done without a standalone backend for all cases except
shared catalogs.

src/backend/storage/ipc/sinval.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.59 2003/08/04 02:40:03 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.60 2003/09/24 18:54:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -73,6 +73,12 @@ SendSharedInvalidMessage(SharedInvalidationMessage *msg)
 /*
  * ReceiveSharedInvalidMessages
  *		Process shared-cache-invalidation messages waiting for this backend
+ *
+ * NOTE: it is entirely possible for this routine to be invoked recursively
+ * as a consequence of processing inside the invalFunction or resetFunction.
+ * Hence, we must be holding no SI resources when we call them.  The only
+ * bad side-effect is that SIDelExpiredDataEntries might be called extra
+ * times on the way out of a nested call.
  */
 void
 ReceiveSharedInvalidMessages(