'GROUP BY' / 'DISTINCT' interaction bug?

Is this a known problem? Is there a work-around?

create table t (c char, i int);
insert into t values ('a', 1);
insert into t values ('a', 1);
insert into t values ('a', 2);
insert into t values ('b', 2);

select distinct on (c, i) c, count(i) from t group by c;
ERROR: Attribute t.i must be GROUPed or used in an aggregate function

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Mark Hollomon
mhh(at)nortelnetworks(dot)com
ESN 451-9008 (302)454-9008