i ran a query with ILIKE but it doesn't use the index.
but i tried following method, and it worked. there is 3 extra lower() overhead but i don't think it will effect the performance.
CREATE INDEX index_name ON mytable (lower(column) varchar_pattern_ops);
SELECT * FROM mytable WHERE lower(column) LIKE lower('beginswith%')
if insert operations are high in database. you use only this index to search case sensitive.
say you want this:
SELECT * FROM mytable WHERE column LIKE 'beGinsWith%'
write this:
SELECT * FROM mytable WHERE lower(column) LIKE lower('beGinsWith%') AND column LIKE 'beGinsWith%'
than query planner will search on index, than scan the resulting bitmap heap.
On 2/22/06, Brendan Duddridge <brendan@xxxxxxxxxxxxxx> wrote:
Hi,Can this technique work with case insensitive ILIKE?It didn't seem to use the index when I used ILIKE instead of LIKE.Thanks,
____________________________________________________________________
Brendan Duddridge | CTO | 403-277-5591 x24 | brendan@xxxxxxxxxxxxxx
ClickSpace Interactive Inc.
Suite L100, 239 - 10th Ave. SE
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http://www.clickspace.comOn Feb 21, 2006, at 1:28 PM, Ibrahim Tekin wrote:this trick did the job.
thanks.On 2/21/06, Alvaro Herrera < alvherre@xxxxxxxxxxxxxxxxx> wrote:Scott Marlowe wrote:
> On Tue, 2006-02-21 at 09:57, Ibrahim Tekin wrote:
> > hi,
> > i have btree index on a text type field. i want see rows which starts
> > with certain characters on that field. so i write a query like this:
> >
> > SELECT * FROM mytable WHERE myfield LIKE 'john%'
> >
> > since this condition is from start of the field, query planner should
> > use index to find such elements but explain command shows me it will
> > do a sequential scan.
> >
> > is this lack of a feature or i am wrong somewhere?
>
> This is an artifact of how PostgreSQL handles locales other than ASCII.
>
> If you want such a query to use an index, you need to back up your
> database, and re-initdb with --locale=C as an argument.
... or you can choose to create an index with the text_pattern_ops
operator class, which would be used in a LIKE constraint regardless of
locale.
http://www.postgresql.org/docs/8.1/static/indexes-opclass.html
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
