From: Bruce Momjian <bruce@momjian.us>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: yigong hu <yigongh@gmail.com>
Cc: splarv@ya.ru
Cc: pgsql-docs@lists.postgresql.org
Subject: Re: explanation for random_page_cost is outdated
Date: Thu, 21 May 2020 20:28:56 -0400
Message-ID: <20200522002856.GC30409@momjian.us> (raw)
In-Reply-To: <20200427161630.GB21731@momjian.us>
References: <20200319205646.GB28431@momjian.us>
<72492300-BFD4-4CCF-9136-20CC41A18A10@ya.ru>
<CAOxFffcourucFqSk+tZA13ErS3XRYkDy6EeaPff4AvHGiEEuug@mail.gmail.com>
<CAFj8pRA35t++NeQ2mbT=3O9=o7M0hrsRZUmPOCRErZR7Am5A_A@mail.gmail.com>
<20200427161630.GB21731@momjian.us>
On Mon, Apr 27, 2020 at 12:16:30PM -0400, Bruce Momjian wrote:
> On Mon, Apr 27, 2020 at 06:02:41AM +0200, Pavel Stehule wrote:
> > > Storage that has a low random read cost relative to sequential, e.g.
> > solid-state drives, might also be better modeled with a value that is close
> > to 1 for random_page_cost.
> >
> >
> > I depends on estimation. Lot of people use random_page_cost as fix of broken
> > estimation. Then configures this value to some strange values. Lot of other
> > queries with good estimation can be worse then.
>
> I have been recommending 1.1 as a value for random_page_cost for SSDs
> for years, and I think it would be helpful to suggest that value, so doc
> patch attached.
Patch applied back through 9.5.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
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Cc: bruce@momjian.us, pavel.stehule@gmail.com, yigongh@gmail.com, splarv@ya.ru, pgsql-docs@lists.postgresql.org
Subject: Re: explanation for random_page_cost is outdated
In-Reply-To: <20200522002856.GC30409@momjian.us>
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