Horton

Re: New GUC to sample log queries

Adrien NAYRAT <adrien.nayrat@anayrat.info>

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From: Adrien Nayrat <adrien.nayrat@anayrat.info>
To: Michael Paquier <michael@paquier.xyz>
Cc: David Rowley <david.rowley@2ndquadrant.com>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Date: 2018-06-24T11:22:55Z
Lists: pgsql-hackers

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On 05/31/2018 03:22 PM, Michael Paquier wrote:
> On Thu, May 31, 2018 at 02:37:07PM +0200, Adrien Nayrat wrote:
>> On 05/31/2018 03:34 AM, David Rowley wrote:
>>> On 31 May 2018 at 06:44, Adrien Nayrat <adrien.nayrat@anayrat.info> wrote:
>>>> Here is a naive SELECT only bench with a dataset which fit in ram (scale factor
>>>> = 100) and PGDATA and log on a ramdisk:
>>>> shared_buffers = 4GB
>>>> seq_page_cost = random_page_cost = 1.0
>>>> logging_collector = on (no rotation)
>>>
>>> It would be better to just: SELECT 1; to try to get the true overhead
>>> of the additional logging code.
>>
>> Right, I wonder why I didn't have the idea :)
> 
> Using prepared statements help also in reducing the load with
> unnecessary planning.
> --
> Michael
> 

Thanks, but the winner is Julien Rouhaud with only ";", I reach 115K TPS on my
laptop :)

Attached third version of the patch with documentation.

-- 
Adrien NAYRAT

Commits

  1. Use pg_strong_random() to select each server process's random seed.

  2. Use a separate random seed for SQL random()/setseed() functions.

  3. Marginal performance hacking in erand48.c.

  4. Fix latent problem with pg_jrand48().

  5. Silence compiler warning

  6. Add log_statement_sample_rate parameter