Views which lead to nested aggregates

I sent this message to pgsql-sql but got no reply and since I'm not
sure if it's a missing feature, bug or something else I'll try
sending it here. Briefly, I'm getting the error
ERROR: ExecAgg: Bad Agg->Target for Agg 0
when layering views to get "nested" aggregates.

I tried the following SQL under PostgreSQL 6.3 and 6.4:

create table contents (
id int not null,
ix int not null,
volid int not null,
level int not null,
bdate datetime not null
);

create view freecount as
select c1.id as id, c1.ix as ix, count(c2.ix) as freeness
from contents c1, contents c2
where c1.volid = c2.volid
and c1.bdate <= c2.bdate
and c1.level >= c2.level
group by c1.id, c1.ix;

Under 6.3, doing the view creation as an ordinary users I got
ERROR: pg_rewrite: Permission denied.
which, if I recall, means postgres view support wasn't quite up to
letting everyone creates views. Doing the view creation as the
postgres superuser succeeded but doing
select * from freecount;
then crashed the backend.

So I installed the recently announced postsgres 6.4 RPM for Linux and
tried again. This time, I could create the view as a normal user and
it worked fine for that simple select. However, what I actually want
to do on top of that view is

create view freetapes as
select id, min(freeness) - 1
from freecount
group by id;

(i.e. do the nested aggregation that SQL syntax won't let me do
directly.) That view creates successfully but doing a
select * from freetapes
produces the error message

ERROR: ExecAgg: Bad Agg->Target for Agg 0

and doing the explicit query

select id, min(freeness) - 1
from freecount
group by id;

gives the same message. I'm not familiar with postgres internals but
it looks as though the internal handling of views is still having
trouble with those two levels of aggregations despite the underlying
queries being OK. As a data point, the view creation and queries work
fine under Informix IDS 7.3 and Sybase. Is this problem with postgres
something which is a fixable bug, a missing feature request that is
planned to arrive soon (maybe it's in 6.5?) or a missing feature which
isn't going to happen any time soon?

--Malcolm

--
Malcolm Beattie <mbeattie(at)sable(dot)ox(dot)ac(dot)uk>
Unix Systems Programmer
Oxford University Computing Services