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From: Alexander Kukushkin <[email protected]>
To: Michael Paquier <[email protected]>
Cc: Sami Imseih <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Christoph Berg <[email protected]>
Cc: Lukas Fittl <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: ma lz <[email protected]>
Subject: Re: query_id: jumble names of temp tables for better pg_stat_statement UX
Date: Tue, 15 Jul 2025 16:48:05 +0200
Message-ID: <CAFh8B==vog16UGpigF5jukg0yZW+MHsvvKG0QBs7gV6cHgqanA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>

Hi,

I totally understand the wish to make pg_stat_statements useful for
workloads that create/drop a ton of temporary tables.
However, when pursuing this goal we impacted other types of totally valid
workloads when tables with the same name exist in different schemas.
Example:
create schema s1;
create table s1.t as select id from generate_series(1, 10) as id;
create schema s2;
create table s1.t as select id from generate_series(1, 1000000) as id;
select count(id) from s1.t;
select count(id) from s2.t;

select * from pg_stat_statements;
userid                     | 10
dbid                       | 5
toplevel                   | t
queryid                    | -8317141500049987426
query                      | select count(id) from s1.t
plans                      | 0
total_plan_time            | 0
min_plan_time              | 0
max_plan_time              | 0
mean_plan_time             | 0
stddev_plan_time           | 0
calls                      | 2
total_exec_time            | 22.577107
min_exec_time              | 0.325021
max_exec_time              | 22.252086000000002
mean_exec_time             | 11.2885535
stddev_exec_time           | 10.963532500000001
rows                       | 2
shared_blks_hit            | 4425

That is, two different queries, accessing two absolutely different tables
(one of them has 100000 times more rows!) were merged together.

Regards,
--
Alexander Kukushkin

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