Re: I don't understand this explain output

Personaly I have no ideia what's happenning but I got a suggestion that may
be a long shot, but try to vacuum de table or database.
>From what I know from pg is every update / delete just happens logic,
meaning that it flag the row updated as old and add a new one to file. Since
you told that this table is updated every minute I thought it might have
something to do with it.

On Tue, May 26, 2009 at 5:32 AM, Ron Arts <ron(dot)arts(at)neonova(dot)nl> wrote:

> Hi,
>
> I am looking at a very simple query (select * from queue),
> which takes forever to finish. I don't understand the output that
> explain tells me:
>
> m=# explain select * from queue;
> QUERY PLAN
> ------------------------------------------------------------
> Seq Scan on queue (cost=0.00..635477.00 rows=1 width=402)
> (1 row)
>
> The cost seems to be very high. It's a small table (only 23 rows)
> and has not seen many modifications since the table was initially
> filled. OTOH many individual records are updated every minute.
>
>
> If I look at anopther table in the same database:
>
> m=# explain select * from contact;
> QUERY PLAN
> -------------------------------------------------------------
> Seq Scan on contact (cost=0.00..183.14 rows=614 width=411)
> (1 row)
>
> and this query finishes very quickly (614 rows).
>
>
> Why would a simple query be so very costly?
>
> Thanks,
> Ron Arts
>
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