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* Very slow search using basic pattern matching
@ 2004-05-18 15:47 Dan Field <dof@llgc.org.uk>
0 siblings, 2 replies; 5+ messages in thread
From: Dan Field @ 2004-05-18 15:47 UTC (permalink / raw)
To: pgsql-sql
I'm trying to use the following statement as part of a search facility
on a site I develop. However the search is taking in excess of 10
seconds some times to return results. I'ts a dual opteron server with a
couple gigs of RAM so should be more than enough to deal with this
database.
SELECT
da_records.RECORD_ID,
da_records.TITLE_EN AS TITLE,
da_records.AUTHOR_EN AS AUTHOR,
da_records.DESCRIPTION_CY AS DESCRIPTION,
da_records.PUBLISHER_CY AS PUBLISHER,
da_records.URL_CY AS URL,
da_records.RECORD_ID,
da_records.KEYWORD_LIST_ID,
da_records.LANGUAGE,
da_records.CONTRIBUTOR_NAME,
da_records.CONTRIBUTOR_EMAIL,
da_records.CONTRIBUTOR_ORGANISATION,
da_records.CONTRIBUTOR_CREDIT,
da_records.DEWEY_LIST_ID,
da_records.LISTING_PRIORITY,
da_records.SUBMITTED_DATE,
da_records.LAST_EDIT_DATE,
da_records.STATUS
FROM
da_records
WHERE
da_records.DESCRIPTION_CY ~* '.*Aberystwyth*.'
OR
da_records.TITLE_CY ~* '.*Aberystwyth*.'
limit 100
Is there a better way of matching the string? (Must be case insensitive)
TIA
--
Dan Field <dof@llgc.org.uk> - Support Programmer: Cymru ar y we
cy_GB: http://www.cymruarywe.org
en_GB: http://www.walesontheweb.org
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: Very slow search using basic pattern matching
@ 2004-05-18 16:12 Bruno Wolff III <bruno@wolff.to>
parent: Dan Field <dof@llgc.org.uk>
1 sibling, 1 reply; 5+ messages in thread
From: Bruno Wolff III @ 2004-05-18 16:12 UTC (permalink / raw)
To: Dan Field <dof@llgc.org.uk>; +Cc: pgsql-sql
On Tue, May 18, 2004 at 16:47:11 +0100,
Dan Field <dof@llgc.org.uk> wrote:
> FROM
> da_records
> WHERE
> da_records.DESCRIPTION_CY ~* '.*Aberystwyth*.'
> OR
> da_records.TITLE_CY ~* '.*Aberystwyth*.'
> limit 100
>
> Is there a better way of matching the string? (Must be case insensitive)
This is going to require a sequential scan and if you aren't going to
hit 100 entries near the beginning of the table, you will be effectively
doing a full scan of the table.
You might try looking at the tsearch2 contrib entry (a package for full text
searching) as that will likely be able to help you out.
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: Very slow search using basic pattern matching
@ 2004-05-18 17:15 Karsten Hilbert <Karsten.Hilbert@gmx.net>
parent: Dan Field <dof@llgc.org.uk>
1 sibling, 0 replies; 5+ messages in thread
From: Karsten Hilbert @ 2004-05-18 17:15 UTC (permalink / raw)
To: pgsql-sql
> WHERE
> da_records.DESCRIPTION_CY ~* '.*Aberystwyth*.'
> OR
> da_records.TITLE_CY ~* '.*Aberystwyth*.'
> limit 100
>
> Is there a better way of matching the string? (Must be case
> insensitive)
Are you sure you can't anchor the search pattern ?
eg ~* '^' || lower('Aberystwyth') || '.*'
That'd allow for use of (functional) indices.
Karsten
--
GPG key ID E4071346 @ wwwkeys.pgp.net
E167 67FD A291 2BEA 73BD 4537 78B9 A9F9 E407 1346
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: Very slow search using basic pattern matching
@ 2004-05-19 11:33 Dan Field <dof@llgc.org.uk>
parent: Bruno Wolff III <bruno@wolff.to>
0 siblings, 1 reply; 5+ messages in thread
From: Dan Field @ 2004-05-19 11:33 UTC (permalink / raw)
To: pgsql-sql
On 18 May 2004, at 17:12, Bruno Wolff III wrote:
> On Tue, May 18, 2004 at 16:47:11 +0100,
> Dan Field <dof@llgc.org.uk> wrote:
>> FROM
>> da_records
>> WHERE
>> da_records.DESCRIPTION_CY ~* '.*Aberystwyth*.'
>> OR
>> da_records.TITLE_CY ~* '.*Aberystwyth*.'
>> limit 100
>>
>> Is there a better way of matching the string? (Must be case
>> insensitive)
>
> This is going to require a sequential scan and if you aren't going to
> hit 100 entries near the beginning of the table, you will be
> effectively
> doing a full scan of the table.
>
> You might try looking at the tsearch2 contrib entry (a package for
> full text
> searching) as that will likely be able to help you out.
OK It looks like the full text search is the way forward here, but I
can only find the tsearch.sql file in contrib. I'm using RedHat EL 3.0
Advanced Server with PG version 7.3-RH.
Is there any documentation available on how to go about creating these
indexes on my text fields?
I'm at a bit of a loss here, Google is failing me sadly
--
Dan Field <dof@llgc.org.uk> - Support Programmer: Cymru ar y we
cy_GB: http://www.cymruarywe.org
en_GB: http://www.walesontheweb.org
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: Very slow search using basic pattern matching
@ 2004-05-19 11:51 Raphael A. Bauer <rbauer@informatik.hu-berlin.de>
parent: Dan Field <dof@llgc.org.uk>
0 siblings, 0 replies; 5+ messages in thread
From: Raphael A. Bauer @ 2004-05-19 11:51 UTC (permalink / raw)
To: Dan Field <dof@llgc.org.uk>; +Cc: pgsql-sql
Dan Field wrote:
> Is there any documentation available on how to go about creating these
> indexes on my text fields?
>
> I'm at a bit of a loss here, Google is failing me sadly
http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/
We made quite good experiences with tsearch2.
The problem for you could be that the case sensititity gets lost.
Raph
^ permalink raw reply [nested|flat] 5+ messages in thread
end of thread, other threads:[~2004-05-19 11:51 UTC | newest]
Thread overview: 5+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2004-05-18 15:47 Very slow search using basic pattern matching Dan Field <dof@llgc.org.uk>
2004-05-18 16:12 ` Bruno Wolff III <bruno@wolff.to>
2004-05-19 11:33 ` Dan Field <dof@llgc.org.uk>
2004-05-19 11:51 ` Raphael A. Bauer <rbauer@informatik.hu-berlin.de>
2004-05-18 17:15 ` Karsten Hilbert <Karsten.Hilbert@gmx.net>
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