Horton

Re: random_page_cost vs seq_page_cost

Peter Eisentraut <peter_e@gmx.net>

View thread
From: Peter Eisentraut <peter_e@gmx.net>
To: Benedikt Grundmann <bgrundmann@janestreet.com>
Cc: pgsql-hackers@postgresql.org
Date: 2012-01-07T21:01:26Z
Lists: pgsql-hackers 
On tor, 2012-01-05 at 10:04 +0000, Benedikt Grundmann wrote:
> We have recently upgrade two of our biggest postgres databases 
> to new hardware and minor version number bump (8.4.5 -> 8.4.9).
> 
> We are experiencing a big performance regression in some queries.
> In those cases the planner seems to choose a nested loop index
> scan instead of hashing the index once and then joining.

There was a planner regression introduced in version 8.4.8, which was
thought to be fixed in 8.4.9.  Maybe you got caught by that.  See

Message-Id: <760C0206-B5F4-4DC6-9296-B7A730B7F403@silentmedia.com>

for some information.  Check if your queries match that pattern.