Re: random_page_cost = 2.0 on Heroku Postgres

On 08/02/12 21:15, Peter van Hardenberg wrote:
> Having read the thread, I don't really see how I could study what a
> more principled value would be.
>
> That said, I have access to a very large fleet in which to can collect
> data so I'm all ears for suggestions about how to measure and would
> gladly share the results with the list.
>
> Peter
>
> On Wed, Feb 8, 2012 at 5:39 PM, Scott Marlowe<scott.marlowe@gmail.com>  wrote:
>> On Wed, Feb 8, 2012 at 5:50 PM, Josh Berkus<josh@agliodbs.com>  wrote:
>>> On 2/7/12 4:59 PM, Peter van Hardenberg wrote:
>>>> Per the thread from last month, I've updated the default
>>>> random_page_cost on Heroku Postgres to reduce the expected cost of a
>>>> random_page on all new databases.
>>> This is because Heroku uses AWS storage, which has fast seeks but poor
>>> throughput compared to internal disk on a standard system, BTW.
>> Also judging by the other thread, it might be something to stop closer
>> to 1.2 to 1.4 or something.
>>
>> --
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>
>
You can execute several queries with the three different values provided
by Scott and Josh.
- SET random_page_cost  = 2.0
First execution of the queries with EXPLAIN ANALYZE
- SET random_page_cost  = 1.4
Second execution of the queries with EXPLAIN ANALYZE
- SET random_page_cost  = 1.2
Second execution of the queries with EXPLAIN ANALYZE

And then, you can compare the pattern behind these queries executions
Regards,

--
Marcos Luis Ortíz Valmaseda
  Sr. Software Engineer (UCI)
  http://marcosluis2186.posterous.com
  http://www.linkedin.com/in/marcosluis2186
  Twitter: @marcosluis2186




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