pg_group problem

Not sure what's going on but I have a problem using pg_group after creating a
group:

testschemas=# select * from pg_group;
groname | grosysid | grolist
---------+----------+---------
(0 rows)

testschemas=# create group testgrp_1 user foo,bar;
CREATE GROUP
testschemas=# select * from pg_group;
ERROR: cache lookup failed for type 2139062143
testschemas=# select * from pg_user;
usename | usesysid | usecreatedb | usesuper | usecatupd | passwd | valuntil | useconfig
----------+----------+-------------+----------+-----------+----------+----------+-----------
software | 1 | t | t | t | ******** | |
foo | 100 | f | f | f | ******** | |
bar | 101 | f | f | f | ******** | |
(3 rows)

testschemas=# select * from pg_group;
ERROR: cache lookup failed for type 2139062143

What's that all about?

Stopping and restarting the backend doesn't make the select of pg_group work,
unsurprisingly.

Okay, narrowed it down to adding users to a group I think. In a fresh build
and install from anoncvs:

testschemas=# create group mytest_grp;
CREATE GROUP
testschemas=# select * from pg_group;
groname | grosysid | grolist
------------+----------+---------
mytest_grp | 100 |
(1 row)

testschemas=# alter group mytest_grp add user foo;
ALTER GROUP
testschemas=# select * from pg_group;
ERROR: cache lookup failed for type 2139062143

Is this something to do with the recent changes to array_in/out perhaps?

--
Nigel J. Andrews
Director

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Logictree Systems Limited
Computer Consultants