Re: Index not used in join.. (example included).

From: Ron Arts <ron(dot)arts(at)neonova(dot)nl>
To: PostgreSQL List - Novice <pgsql-novice(at)postgresql(dot)org>
Subject: Re: Index not used in join.. (example included).
Date: 2009-09-18 14:27:32
Message-ID: 4AB398D4.4080308@neonova.nl
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-novice

Sorry. Maybe I should refrase my question.

I have two tables A and B.
Each table contains a non-unique indexed varchar column.

Table A contains around 500000 rows
table B contains around 4 million rows

for a given value of col there are typically 3 records in A and
20 records in B (give or take)

I want to do something like this:

select a.somecol from A left join B on B.col = A.col where A.date > '2001-01-01';

But this query runs for hours on an eight core server with 4G etc etc.
I configured PG to use 128Mb shared memory, but fiddling with that value
doesn't change much..

And I continuously see the planner choosing for seq scans.

I don't get it.

Ron

--
NeoNova BV
innovatieve internetoplossingen

http://www.neonova.nl Science Park 140 1098 XG Amsterdam
info: 020-5611300 servicedesk: 020-5611302 fax: 020-5611301
KvK Amsterdam 34151241

Op dit bericht is de volgende disclaimer van toepassing:
http://www.neonova.nl/maildisclaimer

In response to

Responses

Browse pgsql-novice by date

  From Date Subject
Next Message Tom Lane 2009-09-18 15:11:48 Re: Index not used in join.. (example included).
Previous Message Tom Lane 2009-09-18 14:10:50 Re: Index not used in join.. (example included)