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Subject: Re: Sample rate added to pg_stat_statements
From: "Andrey M. Borodin" <x4mmm@yandex-team.ru>
In-Reply-To: <20994d10-ab44-4c6b-91bc-c4675cd2e58e@tantorlabs.com>
Date: Tue, 7 Jan 2025 19:15:22 +0500
Cc: Sami Imseih <samimseih@gmail.com>,
 Alexander Korotkov <aekorotkov@gmail.com>,
 Michael Paquier <michael@paquier.xyz>,
 Greg Sabino Mullane <htamfids@gmail.com>,
 pgsql-hackers <pgsql-hackers@postgresql.org>
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To: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>
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> On 7 Jan 2025, at 16:05, Ilia Evdokimov =
<ilya.evdokimov@tantorlabs.com> wrote:
>=20
>> 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 "<=3D", not "<".
>>=20
>>     xact_is_sampled =3D log_xact_sample_rate !=3D 0 &&
>> (log_xact_sample_rate =3D=3D 1 ||
>> pg_prng_double(&pg_global_prng_state) <=3D log_xact_sample_rate);
>>=20
> 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 =3D=3D 0)
+		current_query_sampled =3D =
(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.=