Fix pg_dumpall to restore its ability to dump from ancient servers.

Fix breakage induced by commits d8d3d2a4f3
and 463f2625a5fb183b6a8925ccde98bb3889f921d9: pg_dumpall has crashed when
attempting to dump from pre-8.1 servers since then, due to faulty
construction of the query used for dumping roles from older servers.
The query was erroneous as of the earlier commit, but it wasn't exposed
unless you tried to use --binary-upgrade, which you presumably wouldn't
with a pre-8.1 server.  However commit 463f2625a made it fail always.

In HEAD, also fix additional breakage induced in the same query by
commit 491c029dbc, which evidently wasn't
tested against pre-8.1 servers either.

The bug is only latent in 9.1 because 463f2625a hadn't landed yet, but
it seems best to back-patch all branches containing the faulty query.

Gilles Darold

src/bin/pg_dump/pg_dumpall.c

@@ -700,7 +700,7 @@ dumpRoles(PGconn *conn)
 						  "ORDER BY 2");
 	else
 		printfPQExpBuffer(buf,
-						  "SELECT 0, usename as rolname, "
+						  "SELECT 0 as oid, usename as rolname, "
 						  "usesuper as rolsuper, "
 						  "true as rolinherit, "
 						  "usesuper as rolcreaterole, "
@@ -714,7 +714,7 @@ dumpRoles(PGconn *conn)
 						  "usename = current_user AS is_current_user "
 						  "FROM pg_shadow "
 						  "UNION ALL "
-						  "SELECT 0, groname as rolname, "
+						  "SELECT 0 as oid, groname as rolname, "
 						  "false as rolsuper, "
 						  "true as rolinherit, "
 						  "false as rolcreaterole, "
@@ -724,7 +724,8 @@ dumpRoles(PGconn *conn)
 						  "null::text as rolpassword, "
 						  "null::abstime as rolvaliduntil, "
 						  "false as rolreplication, "
-						  "null as rolcomment, false "
+						  "null as rolcomment, "
+						  "false AS is_current_user "
 						  "FROM pg_group "
 						  "WHERE NOT EXISTS (SELECT 1 FROM pg_shadow "
 						  " WHERE usename = groname) "