Re: Optimization of this SQL sentence

You could try rewriting the query like this:

SELECT MAX(idcomment)
FROM comment c
WHERE idstatus=3 AND ctype=1
AND EXISTS (SELECT 1 FROM ficha vf WHERE idestado IN ('3', '4') AND
vf.idficha = c.idfile);

The planner can then try a backward scan on the comment_pkey index,
which should be quicker than the seq scan assuming that there's a lot of
rows that match the restrictions (idstatus=3 ctype=1 idestado IN ('3',
'4')).

But see comments inline below:

Ruben Rubio wrote:
> CREATE TABLE "comment"
> (
> idcomment int4 NOT NULL DEFAULT
> nextval('comment_idcomment_seq'::regclass),
> score int4,
> title varchar,
> ctext varchar,
> idusuarioficha int4,
> galleta varchar,
> navlang int4,
> cdate timestamp DEFAULT now(),
> idstatus int4,
> ctype int4 NOT NULL,
> idfile int4 NOT NULL,
> nick varchar,
> nombre varchar,
> apellidos varchar,
> dni varchar,
> nacionalidad varchar,
> email varchar,
> telefono varchar,
> code varchar,
> memo varchar,
> c_ip varchar(30),
> codpais char(2),
> replay varchar,
> replaydate timestamp,
> advsent int4,
> usrwarn int4,
> nouserlink int4,
> aviso_confirmacion_15 timestamp,
> aviso_confirmacion_60 timestamp,
> CONSTRAINT comment_pkey PRIMARY KEY (idcomment)
> )

Without knowing anything about you're application, it looks like there's
a some fields in the comment-table that are duplicates of fields in the
ficha-table. Telefono and email for example. You should consider doing
some normalization.

> No indexes in ficha

Except for the implicit idficha_pkey index.

> CREATE TABLE ficha
> (
> ...
> idestado char(1),

If idestado contains numbers (codes of some kind, I presume), you're
better off using the smallint data type.

> ....
> searchengine1 int4,
> searchengine2 int4,
> searchengine3 int4,
> searchengine4 int4,
> searchengine5 int4,
> searchengine6 int4,

Normalization?!

> deseo1 int4,
> deseo2 int4,
> deseo3 int4,
> deseo4 int4,
> deseo5 int4,
> deseo6 int4,

For these as well...

> ...
> lat varchar(25),
> long varchar(25),

Isn't there's a better data type for latitude and longitude? Decimal,
perhaps?

> titulomapa_l0 varchar(255),
> titulomapa_l1 varchar(255),
> titulomapa_l2 varchar(255),
> titulomapa_l3 varchar(255),
> titulomapa_l4 varchar(255),
> titulomapa_l5 varchar(255),
> titulomapa_l6 varchar(255),
> titulomapa_l7 varchar(255),
> titulomapa_l8 varchar(255),
> titulomapa_l9 varchar(255),

Again, normalization...

- Heikki