Re: [GENERAL] Two questions about join performance - Mailing list pgsql-general

From Rudy Gireyev
Subject Re: [GENERAL] Two questions about join performance
Date
Msg-id 199908060452.AAA71810@hub.org
Whole thread Raw
In response to Two questions about join performance  (Roberto Moreda <moreda@sanluis.net>)
List pgsql-general
Well maybe now is a good time to take a look at your
design and see why you have to do this.
There just happens to be a number of great DBAs on
this list as well. :-)

Rudy

On 6 Aug 99, at 2:14, Roberto Moreda wrote:

> Sorry for being so reiterative :)
>
> The planifier isn't perfect for many queries...
> Is there any way (without touch C code) to tell explicitly the plan of a
> query to Postgres?
>
> How can I manage the problem of select a few rows with a boolean atribute
> when they are 5 rows in a table of 100000 rows? I't must to be an index,
> but the optimizer asumes that a Seq Scan is more cheap... yes, yes... I
> know : if I ask for the 100000 then Seq Scan is the solution, but the
> interesting query is the other : to extract the 5 rows with flag='Y' from
> whitin the 100000 rows with the flag='N'.
>
> I'm in a big trouble because of all this.
>
> TIA again.
>
>  Roberto
>
> --
> Roberto Moreda
> Resp. Dpto. Informática Handem/San Luis
> Tlf +34 981 779000
> Fax +34 981 779022
> Pol. Piadela Sur, Autovía A6 Sal.567
> 15300 Betanzos (A Coruña) - España
>
>



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