RE: Need to improve performance

From: "Andrew Snow" <als(at)fl(dot)net(dot)au>
To: "Vassili A Akimov" <vassili(at)erols(dot)com>
Cc: "Pgsql-General(at)Postgresql(dot) Org" <pgsql-general(at)postgresql(dot)org>
Subject: RE: Need to improve performance
Date: 2000-06-23 16:17:05
Message-ID: NHEALMDKDACEIPBNOOOCMEDHCGAA.als@fl.net.au
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-general pgsql-sql

> So we were advised to use "fulltextindex".- chunk
> this fields on single words and make new table with words and oids in
> it. After we made this table its size was 2940360 records. And I tried
> to measure the time:
>
> ....
>
> select f1.id from app_fti f1, app_fti f2 where f1.string~*'visual' and
> f2.string~*'basic' and f1.id=f2.id;

What is causing it to be so slow is the use of regular expression pattern
matching. For reasons I don't know, regular expression evaluation in a
query is fairly slow in PostgreSQL. But since you have (correctly, I think)
made a full text index, why do you still need to use regexp's ?

Replace the ~* operator in the query above with 'LIKE', and you should find
it several times faster.

Please let us know the results of your testing.

- Andrew

In response to

Responses

Browse pgsql-general by date

  From Date Subject
Next Message Joseph Shraibman 2000-06-23 16:36:04 Is this still true?
Previous Message The Hermit Hacker 2000-06-23 16:10:37 Re: app-index in www.pgsql.com

Browse pgsql-sql by date

  From Date Subject
Next Message D'Arcy J.M. Cain 2000-06-23 16:39:10 Re: Using substr with user defined types
Previous Message Oliver Elphick 2000-06-23 16:07:20 Re: Orderby two different columns