update query taking too long - Mailing list pgsql-performance

From Chris
Subject update query taking too long
Date
Msg-id 46834124.5010600@gmail.com
Whole thread Raw
Responses Re: update query taking too long  ("A. Kretschmer" <andreas.kretschmer@schollglas.com>)
Re: update query taking too long  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-performance
Hi all,

I'm trying to do an update of a reasonably large table and it's taking
way too long so I'm trying to work out why and if I need to tweak any
settings to speed it up.

The table is around 3.5 million records.

The query is

update table set domainname=substring(emailaddress from position('@' in
emailaddress));

I've left it running for over 20 minutes and it hasn't finished so I'm
doing something terribly bad but I have no idea what ;)

Maybe there's another way to write the query but I'm not sure how to
make it better.

Most settings are default, I have bumped up shared_buffers a bit to
65536 - I think that works out to 512Meg ? The machine has 2G ram.

Running version 8.1.9.

Any pointers about settings etc are most welcome.

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