Re: idea: log_statement_sample_rate - bottom limit for sampling
От | Tomas Vondra |
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Тема | Re: idea: log_statement_sample_rate - bottom limit for sampling |
Дата | |
Msg-id | 20191106182106.dwdvxalewyydqbx3@development обсуждение исходный текст |
Ответ на | Re: idea: log_statement_sample_rate - bottom limit for sampling (Tomas Vondra <tomas.vondra@2ndquadrant.com>) |
Ответы |
Re: idea: log_statement_sample_rate - bottom limit for sampling
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Список | pgsql-hackers |
On Sun, Aug 04, 2019 at 11:41:54PM +0200, Tomas Vondra wrote: >On Sun, Aug 04, 2019 at 10:48:48PM +0200, Tomas Vondra wrote: >>On Sun, Aug 04, 2019 at 04:25:12PM -0400, Tom Lane wrote: >>>Tomas Vondra <tomas.vondra@2ndquadrant.com> writes: >>>>On Sun, Aug 04, 2019 at 03:16:12PM -0400, Tom Lane wrote: >>>>>Isn't the issue here the interaction between log_transaction_sample_rate >>>>>and log_min_duration_statement? >>> >>>>No, that interaction only affects statement-level sampling. >>> >>>OK, I was confusing the features. >>> >>>>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. >>> >>>So, to clarify: our plan is that a given statement will be logged >>>if any of these various partial-logging features says to do so? >>> >> >>Yes, I think that's the expected behavior. >> >>- did it exceed log_min_duration_statement? -> log it >>- is it part of sampled xact? -> log it >>- maybe sample the statement (to be reverted / reimplemented) >> >>>(And the knock on HEAD's behavior is exactly that it breaks that >>>independence for log_min_duration_statement.) >>> >> >>Yeah. There's no way to use sampling, while ensure logging of all >>queries longer than some limit. >> > >FWIW I've reverted the log_statement_sample_rate (both from master and >REL_12_STABLE). May the buildfarm be merciful to me. > >I've left the log_transaction_sample_rate in, as that seems unaffected >by this discussion. > I've pushed the reworked version of log_statement_sample_rate patch [1]. If I understand correctly, that makes this patch unnecessary, and we should mark it as rejected. Or do we still need it? regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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