That seems like a pretty horrible way to do that query, given the table sizes.
What about something like:
SELECT count(*)
FROM fotos f
LEFT JOIN archivo a USING(archivo)
WHERE a.archivo IS NULL
Incidentally, can someone explain what the "Materialize" subplan does? Is this new in 8.1?
Dmitri
> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org
> [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of
> Sidar López Cruz
> Sent: Wednesday, October 26, 2005 12:27 AM
> To: pgsql-performance@postgresql.org
> Subject: [PERFORM] zero performance on query
>
>
> what happend with postgresql 8.1b4 performance on query?
> please help me !!!
>
> look at this:
> select count(*) from fotos where archivo not in (select archivo from
> archivos)
> Aggregate (cost=4899037992.36..4899037992.37 rows=1 width=0)
> -> Seq Scan on fotos (cost=22598.78..4899037338.07 rows=261716
> -> width=0)
> Filter: (NOT (subplan))
> SubPlan
> -> Materialize (cost=22598.78..39304.22
> rows=805344 width=58)
> -> Seq Scan on archivos (cost=0.00..13141.44
> rows=805344
> width=58)
>
> I WILL DIE WAITING FOR QUERY RESPONSE !!!
> --
> CREATE TABLE archivos ( archivo varchar(20)) WITHOUT OIDS;
> CREATE INDEX archivos_archivo_idx ON archivos USING
> btree(archivo); ~800000 rows
> --
> CREATE TABLE fotos
> (
> cedula varchar(20),
> nombre varchar(100),
> apellido1 varchar(100),
> apellido2 varchar(100),
> archivo varchar(20)
> ) WITHOUT OIDS;
> CREATE INDEX fotos_archivo_idx ON fotos USING btree (archivo);
> CREATE INDEX fotos_cedula_idx ON fotos USING btree (cedula);
> ~500000 rows
>
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