Skip site navigation (1) Skip section navigation (2)

Re: seq scan woes

From: "Dan Langille" <dan(at)langille(dot)org>
To: Rod Taylor <ports(at)rbt(dot)ca>
Cc: Postgresql Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: seq scan woes
Date: 2004-06-07 20:12:40
Message-ID: 40C493F8.1181.48F37175@localhost (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On 7 Jun 2004 at 16:00, Rod Taylor wrote:

> On Mon, 2004-06-07 at 15:45, Dan Langille wrote:
> > A production system has had a query recently degrade in performance.  
> > What once took < 1s now takes over 1s.  I have tracked down the 
> > problem to a working example.
> What changes have you made to postgresql.conf?

Nothing recently (ie. past few months). Nothing at all really.  
Perhaps I need to start tuning that.

> Could you send explain analyse again with SEQ_SCAN enabled but with
> nested loops disabled?



> Off the cuff? I might hazard a guess that effective_cache is too low or
> random_page_cost is a touch too high. Probably the former.

I grep'd postgresql.conf:

#effective_cache_size = 1000    # typically 8KB each
#random_page_cost = 4           # units are one sequential page fetch cost

NOTE: both above are commented out.

Thank you
Dan Langille :
BSDCan -

In response to


pgsql-performance by date

Next:From: Josh BerkusDate: 2004-06-07 20:31:37
Subject: Re: is it possible to for the planner to optimize this form?
Previous:From: Rod TaylorDate: 2004-06-07 20:00:28
Subject: Re: seq scan woes

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group