Re: Log statement sample - take two
От | Tomas Vondra |
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Тема | Re: Log statement sample - take two |
Дата | |
Msg-id | 20191104010807.e2tanu55ny2qqpez@development обсуждение исходный текст |
Ответ на | Log statement sample - take two (Adrien Nayrat <adrien.nayrat@anayrat.info>) |
Ответы |
Re: Log statement sample - take two
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Список | pgsql-hackers |
On Sat, Oct 19, 2019 at 05:02:01PM +0200, Adrien Nayrat wrote: >Hello, > >This patch propose a new way to sample statement to logs. > >As a reminder, this feature was committed in PG12[1] then reverted[2] after the >proposition of log_statement_sample_limit[3] > >The first implementation added a new GUC to sample statement logged by >log_min_duration_statement. Then, we wanted to add the ability to log all >statement whose duration exceed log_statement_sample_limit. > >This was confusing because log_min_duration behaves as a minimum to enable >sampling. While log_statement_sample_limit behave as maximum to disable it.[4] > >Tomas Vondra proposed to use two minimum thresholds: > >> 1) log_min_duration_sample - enables sampling of commands, using the >> existing GUC log_statement_sample_rate >> >> 2) log_min_duration_statement - logs all commands exceeding this > >This patch implement this idea. > >PS: I notice I forgot to mention "Only superusers can change this setting" in >the log_transaction_sample_rate documentation. It attached a second patch to fix >this. > Seems fine to me, mostly. I think the docs should explain how log_min_duration_statement interacts with log_min_duration_sample. Attached is a patch doing that, by adding one para to each GUC, along with some minor rewordings. I think the docs are mixing "sampling" vs. "logging" and "durations" vs. "statements" not sure. I also think the two new sampling GUCs (log_min_duration_sample and log_statement_sample_rate) should be next to each other. We're not ordering the GUCs alphabetically anyway. I plan to make those changes and push in a couple days. regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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