From: Chris Hoover <revoohc@gmail.com>
To: Dan Harris <fbsd@drivefaster.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: Fwd: Help with view performance problem
Date: Thu, 28 Jul 2005 13:34:54 -0400
Message-ID: <1d219a6f05072810341d67c525@mail.gmail.com> (raw)
In-Reply-To: <B0A387FA-9B74-4DB9-9C9F-C8291965A55F@drivefaster.net>
References: <1d219a6f05072708122cf6abeb@mail.gmail.com>
<1d219a6f050727092927746db1@mail.gmail.com>
<1d219a6f0507280738791f0ea3@mail.gmail.com>
<B0A387FA-9B74-4DB9-9C9F-C8291965A55F@drivefaster.net>
I'm alreading running at 1.5. It looks like if I drop the
random_page_cost t0 1.39, it starts using the indexes. Are there any
unseen issues with dropping the random_page_cost this low?
Thanks,
Chris
On 7/28/05, Dan Harris <fbsd@drivefaster.net> wrote:
>
> On Jul 28, 2005, at 8:38 AM, Chris Hoover wrote:
> >
> >
> > I did some more testing, and ran the explain analyze on the problem.
> > In my session I did a set enable_hashjoin = false and then ran the
> > analyze. This caused it to use the indexes as I have been expecting
> > it to do.
> >
> > Now, how can I get it to use the indexes w/o manipulating the
> > environment? What make postgresql want to sequentially scan and use a
> > hash join?
> >
> > thanks,
> >
> > Chris
> >
> > explain analyze with set_hashjoin=false;
> > prob_db=#explain analyze select * from clm_com;
> >
> >
>
> I had something similar to this happen recently. The planner was
> choosing a merge join and seq scan because my 'random_page_cost' was
> set too high. I had it at 3 , and ended up settling at 1.8 to get it
> to correctly use my indices. Once that change was in place, the
> planner did the 'right' thing for me.
>
> Not sure if this will help you, but it sounds similar.
>
> -Dan
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
>
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To: pgsql-performance@postgresql.org
Cc: revoohc@gmail.com, fbsd@drivefaster.net
Subject: Re: Fwd: Help with view performance problem
In-Reply-To: <1d219a6f05072810341d67c525@mail.gmail.com>
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