From: Chao Li <li.evan.chao@gmail.com>
Message-Id: <A1535A8F-65AF-4C3D-ACBE-25891CB5D38B@gmail.com>
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Subject: Re: Add missing stats_reset column to pg_stat_database_conflicts view
Date: Mon, 16 Mar 2026 10:10:34 +0800
In-Reply-To: 
 <CAHGQGwG2OpV-Z-8d9K1owosKhsDKO2kiJVvvkEzWoOMp3NzAcQ@mail.gmail.com>
Cc: Sami Imseih <samimseih@gmail.com>,
 shihao zhong <zhong950419@gmail.com>,
 Kirill Reshke <reshkekirill@gmail.com>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
To: Fujii Masao <masao.fujii@gmail.com>
References: 
 <CAGRkXqS98OebEWjax99_LVAECsxCB8i=BfsdAL34i-5QHfwyOQ@mail.gmail.com>
 <CAA5RZ0vSjCEAuKXhxacnp0ftrYkf9QRcyPK-AvTi_otFVDWphA@mail.gmail.com>
 <CAHGQGwEeGUQtj7TOznM2_O2uV-g6iOa1UBBTBfyugJ-nSoS89Q@mail.gmail.com>
 <CALdSSPi4apueVqgnJEZqpy6O0HSEPUiUzf=vTLPPijsQLob2Eg@mail.gmail.com>
 <CAGRkXqQ0qBHTcD=UZ7_GTLsgn+W-=1c8suMJ3yWZb2eP4m0fBg@mail.gmail.com>
 <CAA5RZ0ta3y==2AStFyo-SYyJ2ztd3ZiurN1HQR9gzDTKVtgUDg@mail.gmail.com>
 <CAGRkXqRVDuhXNCvQ=j-+5KCu+Gcar_h5OeHTaMaVKF-FLV2YvQ@mail.gmail.com>
 <CAHGQGwHaHnRrz9hqpDdn984mqToJDdkjMRVvEXXgFwCnXJb89Q@mail.gmail.com>
 <7C8AB453-8353-4D79-AA97-62177D631A18@gmail.com>
 <CAA5RZ0uStx0cWUCNPDPhBprAVmcdOX-uuKd9B_W9qLa6Tsp46w@mail.gmail.com>
 <CAHGQGwF3=y-j5LxHdXtthEsmJYY5U6WtcAsgwbestfCtNvvuaw@mail.gmail.com>
 <CAA5RZ0uy79o0vr2=LeRHS2MZ7V6HGOCsys6YAbmmj3BW8tnziw@mail.gmail.com>
 <126F5EBD-16EB-4786-8A65-8D1BCC0F20D7@gmail.com>
 <CAHGQGwG2OpV-Z-8d9K1owosKhsDKO2kiJVvvkEzWoOMp3NzAcQ@mail.gmail.com>
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> On Mar 13, 2026, at 21:25, Fujii Masao <masao.fujii@gmail.com> wrote:
>=20
> On Fri, Mar 13, 2026 at 5:47=E2=80=AFPM Chao Li =
<li.evan.chao@gmail.com> wrote:
>>=20
>>=20
>>=20
>>> On Mar 13, 2026, at 04:39, Sami Imseih <samimseih@gmail.com> wrote:
>>>=20
>>>> I also made some cosmetic indentation fixes in the docs.
>>>> The v6 patch is attached.
>>>=20
>>> Just one more minor comment fix I noticed.
>>>=20
>>> "Test that reset works for pg_stat_database"
>>>=20
>>> to:
>>>=20
>>> "Test that reset works for pg_stat_database and =
pg_stat_database_conflicts"
>>>=20
>>> --
>>> Sami
>>> <v7-0001-Add-stats_reset-column-to-pg_stat_database_confli.patch>
>=20
> I've pushed the patch. Thanks!
>=20
>=20
>> I still saw (SELECT current_database()) in v7. Does it have any =
special meaning than just current_database()?
>=20
> No. I think it was used by the patch simply because the existing tests
> for stats reset already use it.
>=20
> Regards,
>=20
> --=20
> Fujii Masao

Hi Fujii-san,

If the only reason for using (SELECT current_database()) is to follow =
the existing code, would it make sense to update the code to use =
current_database() instead?

Looking at the execution plans below:
```
evantest=3D# explain select (select current_database());
                    QUERY PLAN
---------------------------------------------------
 Result  (cost=3D0.01..0.02 rows=3D1 width=3D64)
   InitPlan expr_1
     ->  Result  (cost=3D0.00..0.01 rows=3D1 width=3D64)
(3 rows)

evantest=3D# explain select current_database();
                QUERY PLAN
-------------------------------------------
 Result  (cost=3D0.00..0.01 rows=3D1 width=3D64)
(1 row)
```

The nested SELECT introduces an unnecessary InitPlan, which adds extra =
work to execute.

Another point is that the nested SELECT may mislead users or code =
readers into thinking it is required. For example, I often look at =
regression test scripts to check how SQL statements are used in =
practice, and I consider them an important source of reference. Because =
of that, I think it's better for the test scripts to demonstrate the =
simplest and most appropriate usage when possible.

I searched through the test scripts, and it looks like only stats.sql =
uses this pattern. So I attached a small patch that replaces all (SELECT =
current_database()) with current_database().

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/


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