Message-ID: <47EA5B4D.5000300@geizhals.at>
Date: Wed, 26 Mar 2008 15:18:53 +0100
From: Marinos Yannikos <mjy@geizhals.at>
User-Agent: Thunderbird 2.0.0.12 (Windows/20080213)
MIME-Version: 1.0
To: pgsql-performance@postgresql.org
Subject: 1-/2-dimensional indexes for common columns, rationale?
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit

Hello,

we have several indexes such as:

create index foo1 on bla (a);
create index foo2 on bla (b);
create index foo3 on bla (a,b);

They are all used often by frequently used queries (according to 
pg_statio_user_indexes), but we need somewhat higher INSERT/UPDATE 
performance (having tuned most other things) so we'd like to remove some.

Which of the above would generally speaking be most redundant / best to 
remove? Is a 2-dimensional index always much slower than a 1-dimensional 
with the first column for queries on the first column? Any other 
suggestions?

Thanks,
  Marinos