Re: Cost problem

On 8/2/05, Victor <victor(at)ambra(dot)ro> wrote:
> Hello.
>
> I use psql (PostgreSQL) 7.4.5.
>
> I have a cost problem.
>
> A simple select lasts too long.
> I have a table with aprox 900 rows.
> All rows are deleted and reinserted once a minute.
>
> EXPLAIN SELECT * FROM logati;
> QUERY PLAN
> -------------------------------------------------------------------
> Seq Scan on logati (cost=0.00..100741.22 rows=1198722 width=340)
>
>
> EXPLAIN ANALYZE SELECT * FROM logati;
> QUERY PLAN
> -----------------------------------------------------------------------------------------------------------------------
> Seq Scan on logati (cost=0.00..100741.22 rows=1198722 width=340)
> (actual time=35927.945..35944.272 rows=842 loops=1)
> Total runtime: 35945.840 ms
> (2 rows)
>
>
> Tha problem is that "EXPLAIN" function raports that the table has
> 1198722 rows.
> But the table has only 836 rows and the select lasts a lot.
>
> If I recreate the table the number of rows is ok and the select is quick
> for some time, but it becomes slower in time.
>
> How can I fix this?
>
> PS: The table has a index but no primary key.
>
> Thank you
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
>

execute ANALYZE in the table from time to time... And maybe and
better vacuum...

--
Atentamente,
Jaime Casanova
(DBA: DataBase Aniquilator ;)