Horton

RE: Log a sample of transactions

Kuroda, Hayato <kuroda.hayato@jp.fujitsu.com>

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From: "Kuroda, Hayato" <kuroda.hayato@jp.fujitsu.com>
To: 'Adrien NAYRAT' <adrien.nayrat@anayrat.info>, "'pgsql-hackers@lists.postgresql.org'" <pgsql-hackers@lists.postgresql.org>
Date: 2019-01-28T01:53:51Z
Lists: pgsql-hackers

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  1. Tweak docs for log_statement_sample_rate

Dear Adrien,

>> * xact_is_sampled is left at the end of a transaction.
>> Should the parameter be set to false at the lowest layer of the transaction system?
>> I understand it is unnecessary for the functionality, but it have more symmetry.
>
> Yes, it is not necessary. I wonder what is more important : keep some 
>kind of symmetry or avoid unnecessary code (which can be source of mistake)?

>> 
>> * check_log_duration should be used only when postgres check the duration.
>> But I'm not sure a new function such as check_is_sampled is needed because A processing in new function will be as almost same as check_log_duration.

> I agree, I asked myself the same question and I preferred to keep code 
simple.

I think your point is also correct.
You should inquire superior reviewers or committers because I cannot judge which one is better.


BTW, I give you a suggestion about a test.
This parameter enables users to log statements randomly, hence adding some tests is very difficult.
Perhaps Only three cases are available:

* When log_transaction_sample_rate is set to 1, all statements are logged.
* When the parameter is set to 0, they are never logged.
* When the parameter change to 0 inside the transaction, logging is immediately stopped.


Best Regards,
Hayato Kuroda
Fujitsu LIMITED