Re: group by will not use an index?

> For the reasons indicated (that is, MVCC), PG can not do a DISTINCT or the
> equivalent
> GROUP BY from index values alone.

Ok, that makes sense. Thanks for the help everybody!

If this table is large, perhaps you could denormalize and maintain a
> summary table with date (using truncation) and count, updated with
> triggers on the original table. This table will presumably have a
> small number of rows at the cost of doubling the times for updates,
> inserts, and deletes.

Well, the inserted time, at least, is never updated, and deletions are very
rare (never, so far), so I'll have a look at doing things that way. Thanks!