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,
contentsc2       where c1.volid = c2.volid         and c1.bdate <= c2.bdate         and c1.level >= c2.level
groupby 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@sable.ox.ac.uk>
Unix Systems Programmer
Oxford University Computing Services