Re: New GUC to sample log queries

On 10/07/18 20:34, Adrien Nayrat wrote:
> On 06/27/2018 11:13 PM, Adrien Nayrat wrote:
>>> 3) Is it intentional to only sample with log_min_duration_statement and
>>> not also with log_duration? It seems like it should affect both. In
>>> both cases, the name is too generic. Something called "log_sample_rate"
>>> should sample **everything**.
>> I do not think it could be useful to sample other case such as log_duration.
>>
>> But yes, the GUC is confusing and I am not comfortable to introduce a new GUC in
>> my initial patch.
>>
>> Maybe we should adapt current GUC with something like :
>>
>> log_min_duration_statement = <time>,<sample rate>>
>> This give :
>>
>> log_min_duration_statement = 0,0.1
>>
>> Equivalent to :
>> log_min_duration_statement = 0
>> log_sample_rate = 0.1
>>
>> Thought?
>>
>
> After reflection it seems a bad idea :
>
> * it breaks compatibility with external tools
> * it introduce a kind of "composite" GUC which may add complexity to use. For
> example in pg_settings view.

Yes, I think that was a very bad idea.

> What do you think of : log_min_duration_statement_sample ?

Hmm. Not sure if that last word should be _sample, _sampling, _rate, or
a combination of those.

> Is it too long?

I introduced idle_in_transaction_session_timeout, so I'm not one to say
a setting name is too long :)
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