Re: Planner should use index on a LIKE 'foo%' query

Hi,

Le samedi 28 juin 2008, Moritz Onken a écrit :
> select count(*)
> from result
> where exists
> (select * from item where item.url LIKE result.url || '%' limit 1);
>
> which basically returns the number of items which exist in table
> result and match a URL in table item by its prefix.

It seems you could benefit from the prefix project, which support indexing
your case of prefix searches. Your query would then be:
SELECT count(*) FROM result r JOIN item i ON r.url @> i.url;

The result.url column would have to made of type prefix_range, which casts
automatically to text when needed.

Find out more about the prefix projects at those urls:
http://pgfoundry.org/projects/prefix
http://prefix.projects.postgresql.org/README.html

Regards,
--
dim