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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Adrien Nayrat <adrien.nayrat@anayrat.info>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: idea: log_statement_sample_rate - bottom limit for sampling
Date: Sun, 4 Aug 2019 21:58:23 +0200
Message-ID: <20190804195823.qi7vntgybfgitdnn@development> (raw)
In-Reply-To: <25079.1564946172@sss.pgh.pa.us>
References: <156292912396.1365.3073279552263868317.pgcf@coridan.postgresql.org>
	<156292957348.1365.8079060287740507529.pgcf@coridan.postgresql.org>
	<CAFj8pRB=bHQ=H3wbX1Qs9ViM-JeywvFm_k-ey1cOmSbWe=O0ew@mail.gmail.com>
	<20190727221948.irg6sfqh57dynoc7@development>
	<4540bafe-1b23-a6ce-a313-f3b03bb418df@anayrat.info>
	<cfe72bab-dc4c-d194-4ea2-ac9dc89d6243@anayrat.info>
	<20190801100445.yo5v3pdxelijztzm@development>
	<3f6b75ea-03bb-7c35-1f20-e989f4b7f9ac@anayrat.info>
	<20190804191037.em6rmlvxjpcsjtqu@development>
	<25079.1564946172@sss.pgh.pa.us>

On Sun, Aug 04, 2019 at 03:16:12PM -0400, Tom Lane wrote:
>Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>> OK, I have the revert ready. The one thing I'm wondering about is
>> whether we need to revert log_transaction_sample_rate too? I think it's
>> pretty much independent feature, so I think we can keep that. Opinions?
>
>Isn't the issue here the interaction between log_transaction_sample_rate
>and log_min_duration_statement?  Seems like we have that question
>regardless of whether log_statement_sample_limit exists.
>

No, that interaction only affects statement-level sampling.

For transaction-level sampling we do the sampling independently of the
statement duration, i.e. we when starting a transaction we determine
whether the whole transaction will be sampled. It has nothing to do with
the proposed log_statement_sample_limit.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services 





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