Re: bad estimates / non-scanning aggregates

Bruno Wolff III wrote:
> On Thu, Aug 28, 2003 at 17:10:31 -0700,
>   Ken Geis <kgeis@speakeasy.org> wrote:
>
>>The query I want to run is
>>
>>select stock_id, min(price_date) from day_ends group by stock_id;
>
> The fast way to do this is:
>
> select distinct on (stock_id) stock_id, price_date
>   order by stock_id, price_date;

Not according to the optimizer!  Plus, this is not guaranteed to return
the correct results.

  Unique  (cost=3711244.30..3795942.42 rows=6366 width=8)
    ->  Sort  (cost=3711244.30..3753593.36 rows=16939624 width=8)
          Sort Key: stock_id, price_date
          ->  Seq Scan on day_ends  (cost=0.00..361892.24 rows=16939624
width=8)