> On Mar 13, 2026, at 21:25, Fujii Masao <[email protected]> wrote: > > On Fri, Mar 13, 2026 at 5:47 PM Chao Li <[email protected]> wrote: >> >> >> >>> On Mar 13, 2026, at 04:39, Sami Imseih <[email protected]> wrote: >>> >>>> I also made some cosmetic indentation fixes in the docs. >>>> The v6 patch is attached. >>> >>> Just one more minor comment fix I noticed. >>> >>> "Test that reset works for pg_stat_database" >>> >>> to: >>> >>> "Test that reset works for pg_stat_database and pg_stat_database_conflicts" >>> >>> -- >>> Sami >>> <v7-0001-Add-stats_reset-column-to-pg_stat_database_confli.patch> > > I've pushed the patch. Thanks! > > >> I still saw (SELECT current_database()) in v7. Does it have any special >> meaning than just current_database()? > > No. I think it was used by the patch simply because the existing tests > for stats reset already use it. > > Regards, > > -- > 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=# explain select (select current_database());
QUERY PLAN
---------------------------------------------------
Result (cost=0.01..0.02 rows=1 width=64)
InitPlan expr_1
-> Result (cost=0.00..0.01 rows=1 width=64)
(3 rows)
evantest=# explain select current_database();
QUERY PLAN
-------------------------------------------
Result (cost=0.00..0.01 rows=1 width=64)
(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/
v1-0001-regress-remove-unnecessary-subquery-around-curren.patch
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