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Re: pgsql: Document random page cost is only 4x seqeuntial, and not 40x.

From: Thom Brown <thom(at)linux(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: pgsql-committers(at)postgresql(dot)org
Subject: Re: pgsql: Document random page cost is only 4x seqeuntial, and not 40x.
Date: 2012-02-14 22:58:52
Message-ID: CAA-aLv6WQVC0PP4pQYxTpQprBJW1=bt47kbMZ8fD1kHwkP0UoQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-committers
On 14 February 2012 22:46, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> On Tue, Feb 14, 2012 at 10:44:08PM +0000, Thom Brown wrote:
>> On 14 February 2012 21:55, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> > Document random page cost is only 4x seqeuntial, and not 40x.
>> >
>> > Branch
>> > ------
>> > master
>> >
>> > Details
>> > -------
>> > http://git.postgresql.org/pg/commitdiff/c1d9df4fa227781b31be44a5a3024865a7f48049
>> >
>> > Modified Files
>> > --------------
>> > doc/src/sgml/config.sgml |   20 ++++++++++++++++++++
>> > 1 files changed, 20 insertions(+), 0 deletions(-)
>>
>> This change does say that it is 40 times slower:
>>
>> "The default value can be thought of as modeling random access as 40
>> times slower than sequential..."
>
> I meant to say that it documents why we have a default of 4x, not 40x.
> (In fact, real world, it is probably 100x.)

Hmmm.. okay.  I haven't managed to test that myself, but I'll take
your word for it. :)

-- 
Thom

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