Re: Yet another 'why does it not use my index' question. - Mailing list pgsql-performance

On Wed, May 07, 2003 at 09:11:49 -0500,
  Ryan <pgsql-performance@seahat.com> wrote:
> I wanted to do the following:
>
> midas=# explain analyze select * from zip where zip in
>  (select option_value from client_options where option_name = 'ZIP_CODE' );

Until 7.4 comes out IN will be slow and you should use a join to do this.

> midas=# explain analyze select * from zip z, client_options c where
> c.option_name = 'ZIP_CODE' and c.option_value = z.zip;

I think the problem here might be related to option_value being text
and zip being char varying. This might prevent an index from being used
to do the join.