Re: Query-Planer from 6seconds TO DAYS - Mailing list pgsql-performance

From Jeff Janes
Subject Re: Query-Planer from 6seconds TO DAYS
Date
Msg-id CAMkU=1ydScGzm6XBDPSS0v+w8tKg2HCYCLSTg1OSFGAu2O=mhA@mail.gmail.com
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In response to Re: Query-Planer from 6seconds TO DAYS  ("Kevin Grittner" <kgrittn@mail.com>)
List pgsql-performance
On Fri, Oct 26, 2012 at 8:30 AM, Kevin Grittner <kgrittn@mail.com> wrote:
> ktm@rice.edu wrote:
>
>> You have the sequential_page_cost = 1 which is better than or equal
>> to the random_page_cost in all of your examples. It sounds like you
>> need a sequential_page_cost of 5, 10, 20 or more.
>
> The goal should be to set the cost factors so that they model actual
> costs for you workload in your environment.

Unfortunately the random_page_cost is getting multiplied by an
estimated page count which is 4 orders of magnitude too high.
random_page_cost and seq_page_cost (and enable_seqscan) might not be
the right knobs, but they are the knobs that currently exist.

Cheers,

Jeff


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