From: Joshua D. Drake <jd@commandprompt.com>
To: Mikko Partio <mpartio@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Slow indexscan
Date: Wed, 20 Jun 2007 09:01:55 -0700
Message-ID: <46794F73.5010201@commandprompt.com> (raw)
In-Reply-To: <2ca799770706200855w1a6b6a7cy8526b9be0ef9c97c@mail.gmail.com>
References: <2ca799770706200702y1074f066s61279b67f93315d0@mail.gmail.com>
<17907.1182352197@sss.pgh.pa.us>
<2ca799770706200855w1a6b6a7cy8526b9be0ef9c97c@mail.gmail.com>
Mikko Partio wrote:
>
>
> On 6/20/07, *Tom Lane* <tgl@sss.pgh.pa.us <mailto:tgl@sss.pgh.pa.us>> wrote:
>
> "Mikko Partio" <mpartio@gmail.com <mailto:mpartio@gmail.com>> writes:
>
> > Index Scan using tbl_20070601_pkey on tbl_20070601 t1
> > (cost=0.00..365.13rows=13 width=137) (actual time=
> > 120.83..10752.64 rows=539 loops=1)
> > Index Cond: ((validtime >= 20070602000000::bigint) AND
> (validtime <=
> > 20070602235500::bigint) AND (latitude = 60.2744::double
> precision) AND
> > (longitude = 26.4417::double precision))
> > Filter: (parname = 'temperature'::character varying)
>
> You do realize that's going to scan the entire index range from
> 20070602000000 to 20070602235500?
>
> If this is a typical query you'd be better off putting the lat/long
> columns first in the index.
>
> regards, tom lane
>
>
>
> Thanks for the reply.
>
> Adding a new index does not speed up the query (although the planner
> decides to use the index):
>
> db=# create index tbl_20070601_latlonvalidpar_index on tbl_20070601
> (latitude,longitude,validtime,parname);
> CREATE INDEX
>
> db=# explain analyze select * from tbl_20070601 where validtime between
> 20070602000000 and 20070602235500 and latitude= 60.2744 and
> longitude=26.4417 and parname in ('temperature');
>
> QUERY PLAN
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Index Scan using tbl_20070601_latlonvalidpar_index on tbl_20070601 t1
> (cost=0.00..29.18 rows=13 width=137) (actual time=3471.94..31542.90
> rows=539 loops=1)
> Index Cond: ((latitude = 60.2744::double precision) AND (longitude =
> 26.4417::double precision) AND (validtime >= 20070602000000::bigint) AND
> (validtime <= 20070602235500::bigint) AND (parname =
> 'temperature'::character varying))
> Total runtime: 31544.48 msec
> (3 rows)
>
>
> This is a very typical query and therefore it should be made as fast as
> possible. There are several tables like this rowcount ranging from 3
> million to 13 million. I have some possibilities to modify the queries
> as well as the tables, but the actual table structure is hard coded.
>
> Any other suggestions?
Try increasing your default_statistics_target and rerunning explain
analyze. Secondly try increasing your work_mem.
Joshua D. Drake
>
> Regards
>
> MP
>
>
--
=== The PostgreSQL Company: Command Prompt, Inc. ===
Sales/Support: +1.503.667.4564 || 24x7/Emergency: +1.800.492.2240
Providing the most comprehensive PostgreSQL solutions since 1997
http://www.commandprompt.com/
Donate to the PostgreSQL Project: http://www.postgresql.org/about/donate
PostgreSQL Replication: http://www.commandprompt.com/products/
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: jd@commandprompt.com, mpartio@gmail.com, tgl@sss.pgh.pa.us
Subject: Re: Slow indexscan
In-Reply-To: <46794F73.5010201@commandprompt.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox