Integrate autovacuum functionality into the backend. There's still a

few loose ends to be dealt with, but it seems to work.  Alvaro Herrera,
based on the contrib code by Matthew O'Connor.

src/backend/utils/init/miscinit.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.145 2005/07/04 04:51:50 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.146 2005/07/14 05:13:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -32,6 +32,7 @@
 #include "catalog/pg_authid.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
+#include "postmaster/autovacuum.h"
 #include "storage/fd.h"
 #include "storage/ipc.h"
 #include "storage/pg_shmem.h"
@@ -394,7 +395,7 @@ void
 InitializeSessionUserIdStandalone(void)
 {
 	/* This function should only be called in a single-user backend. */
-	AssertState(!IsUnderPostmaster);
+	AssertState(!IsUnderPostmaster || IsAutoVacuumProcess());
 
 	/* call only once */
 	AssertState(!OidIsValid(AuthenticatedUserId));