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help / color / mirror / Atom feedFrom: Andrey M. Borodin <[email protected]>
To: Ilia Evdokimov <[email protected]>
Cc: Sami Imseih <[email protected]>
Cc: Alexander Korotkov <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Greg Sabino Mullane <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: Sample rate added to pg_stat_statements
Date: Tue, 7 Jan 2025 19:15:22 +0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
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> On 7 Jan 2025, at 16:05, Ilia Evdokimov <[email protected]> wrote:
>
>> 1. This code seems a little different from your patch. It is trying to avoid engaging PRNG. I'm not sure it's a good idea, but still. Also, it uses "<=", not "<".
>>
>> xact_is_sampled = log_xact_sample_rate != 0 &&
>> (log_xact_sample_rate == 1 ||
>> pg_prng_double(&pg_global_prng_state) <= log_xact_sample_rate);
>>
> Are we sure we're discussing the same patch? Because these remarks refer to the 5 version of the patch, which I abandoned due to your remarks.
Yes. v6 has this code
+ if (nesting_level == 0)
+ current_query_sampled = (pg_prng_double(&pg_global_prng_state) < pgss_sample_rate);
while upstream has code that I cited. And logic is slightly different.
Best regards, Andrey Borodin.
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