From: Julien Cigar <jcigar@ulb.ac.be>
To: pgsql-sql@postgresql.org
Subject: bad plan
Date: Thu, 05 Apr 2012 13:38:38 +0200
Message-ID: <4F7D843E.4060304@ulb.ac.be> (raw)
Hello,
I have an extremely bad plan for one of my colleague's query. Basically
PostgreSQL chooses to seq scan instead of index scan. This is on:
antabif=# select version();
version
----------------------------------------------------------------------------------------------------------
PostgreSQL 9.0.7 on amd64-portbld-freebsd8.2, compiled by GCC cc (GCC)
4.2.1 20070719 [FreeBSD], 64-bit
The machines has 4GB of RAM with the following config:
- shared_buffers: 512MB
- effective_cache_size: 2GB
- work_mem: 32MB
- maintenance_work_mem: 128MB
- default_statistics_target: 300
- temp_buffers: 64MB
- wal_buffers: 8MB
- checkpoint_segments = 15
The tables have been ANALYZE'd. I've put the EXPLAIN ANALYZE on:
- http://www.pastie.org/3731956 : with default config
- http://www.pastie.org/3731960 : this is with enable_seq_scan = off
- http://www.pastie.org/3731962 : I tried to play on the various cost
settings but it's doesn't change anything, except setting
random_page_cost to 1 (which will lead to bad plans for other queries,
so not a solution)
- http://www.pastie.org/3732035 : with enable_hashagg and
enable_hashjoin to false
I'm currently out of idea why PostgreSQL still chooses a bad plan for
this query ... any hint :) ?
Thank you,
Julien
--
No trees were killed in the creation of this message.
However, many electrons were terribly inconvenienced.
Attachments:
[text/x-vcard] jcigar.vcf (290B, ../4F7D843E.4060304@ulb.ac.be/2-jcigar.vcf)
download | inline:
begin:vcard
fn:Julien Cigar
n:Cigar;Julien
org;quoted-printable:Belgian Biodiversity Platform;ULB (Universit=C3=A9 Libre de Bruxelles)
adr:;;;Brussels;;;Belgium
email;internet:jcigar@ulb.ac.be
tel;work:+32(0)26505752
x-mozilla-html:FALSE
url:http://www.biodiversity.be
version:2.1
end:vcard
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-sql@postgresql.org
Cc: jcigar@ulb.ac.be
Subject: Re: bad plan
In-Reply-To: <4F7D843E.4060304@ulb.ac.be>
* 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