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From: Alexander Korotkov <aekorotkov@gmail.com>
Date: Wed, 20 May 2026 23:29:07 +0300
Message-ID: 
 <CAPpHfdvht=_VcpDybYvwon96Enh=-S-9wGLGPzbu+6_5QmwmwQ@mail.gmail.com>
Subject: Re: Fix SPLIT PARTITION bound-overlap bug and other improvements
To: Chao Li <li.evan.chao@gmail.com>
Cc: Dmitry Koval <d.koval@postgrespro.ru>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
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On Wed, May 20, 2026 at 2:46=E2=80=AFPM Alexander Korotkov <aekorotkov@gmai=
l.com> wrote:
> On Wed, May 20, 2026 at 9:29=E2=80=AFAM Chao Li <li.evan.chao@gmail.com> =
wrote:
> > > On May 20, 2026, at 14:19, Alexander Korotkov <aekorotkov@gmail.com> =
wrote:
> > > On Wed, May 20, 2026 at 2:37=E2=80=AFAM Chao Li <li.evan.chao@gmail.c=
om> wrote:
> > >>> On May 19, 2026, at 19:00, Alexander Korotkov <aekorotkov@gmail.com=
> wrote:
> > >>> On Tue, May 19, 2026 at 5:50=E2=80=AFAM Chao Li <li.evan.chao@gmail=
.com> wrote:
> > >>>>> On May 18, 2026, at 20:04, Alexander Korotkov <aekorotkov@gmail.c=
om> wrote:
> > >>>>>
> > >>>>> On Mon, May 18, 2026 at 2:57=E2=80=AFPM Chao Li <li.evan.chao@gma=
il.com> wrote:
> > >>>>>>> <v3-0003-Clarify-SPLIT-PARTITION-bound-requirements-in-doc.patc=
h><v3-0001-Fix-SPLIT-PARTITION-range-bound-validation-with-D.patch><v3-0002=
-Fix-SPLIT-PARTITION-hint-for-DEFAULT-partition-bo.patch><v3-0004-Reject-de=
generate-SPLIT-PARTITION-with-DEFAULT-pa.patch>
> > >>>>>>
> > >>>>>> v3-0001 through v3-0003 look good to me.
> > >>>>>>
> > >>>>>> For v3-0004, I have a suspicion, but it's late here and my brain=
 is getting slow, so I would like to study it more tomorrow.
> > >>>>>
> > >>>>> Sure, take your time.
> > >>>>>
> > >>>>> ------
> > >>>>> Regards,
> > >>>>> Alexander Korotkov
> > >>>>> Supabase
> > >>>>
> > >>>> My suspicion was that check_split_partition_not_same_bound() now h=
as two paths. The RANGE path honors collation, while the LIST path does not=
. So I spent some time creating a test that uses a case-insensitive collati=
on:
> > >>>> ```
> > >>>> evantest=3D# create collation case_insensitive (provider=3Dicu, lo=
cale=3D'und-u-ks-level2', deterministic =3D false);
> > >>>> CREATE COLLATION
> > >>>> evantest=3D# create table t (b text collate case_insensitive) part=
ition by list (b);
> > >>>> CREATE TABLE
> > >>>> evantest=3D# create table tp_ab partition of t for values in ('a',=
 'b');
> > >>>> CREATE TABLE
> > >>>> evantest=3D# alter table t split partition tp_ab into
> > >>>> evantest-#   (partition tp_a for values in ('a', 'A'),
> > >>>> evantest(#   partition tp_default default);
> > >>>> ERROR:  cannot split partition "tp_ab" only to add a DEFAULT parti=
tion
> > >>>> LINE 2:   (partition tp_a for values in ('a', 'A'),
> > >>>>                    ^
> > >>>> DETAIL:  The non-DEFAULT partition would keep the same partition b=
ound.
> > >>>> HINT:  Use CREATE TABLE ... PARTITION OF ... DEFAULT to add a DEFA=
ULT partition.
> > >>>> ```
> > >>>>
> > >>>> In this test, the split partition=E2=80=99s bound is ('a', 'b'), a=
nd the new partition=E2=80=99s bound is ('a', 'A'). Their list lengths are =
both 2, but the two bounds are actually different, because 'a' and 'A' are =
considered equal by the collation.
> > >>>>
> > >>>> So, in the LIST path, since check_partition_bounds_for_split_list(=
) has already ensured that the new partition=E2=80=99s bound is contained w=
ithin the split partition=E2=80=99s bound, we need to check the reverse dir=
ection as well. Whether the split partition=E2=80=99s bound is also contain=
ed in the new partition=E2=80=99s bound. If yes, the two bounds are identic=
al.
> > >>>>
> > >>>> See the attached v4 for my changes for 0004. 0001-0003 are unchang=
ed. Since 0001 and 0003 are independent of 0004, maybe they can be pushed f=
irst.
> > >>>
> > >>> I've pushed 0001-0003.
> > >>
> > >> Thanks for pushing them.
> > >>
> > >>> Thank you for discovering the collation issue
> > >>> in 0004.  Note that original approach of using
> > >>> partition_bounds_equal() can't handle different collations too (as =
it
> > >>> internally uses datumIsEqual()).
> > >>
> > >> Yes, I realized that while reviewing v3. That=E2=80=99s reason I did=
n=E2=80=99t get back v2 and only worked again based on v3.
> > >>
> > >>> I've revised the remaining patch:
> > >>> made function header comment a bit more detailed
> > >>
> > >> This part looks good to me.
> > >>
> > >>> and added additional
> > >>> regression tests.  Please, check.
> > >>>
> > >>
> > >> But I don=E2=80=99t see any change for regression test between v4 an=
d v5. Maybe you forgot to save your changes?
> > >
> > > Sorry, I just mess up, no changes in tests.
> > > I'm going to push this if no objection.
> > >
> >
> > No worries. Then v5 looks good to me.
>
> Thank you, pushed.

Uhhh, most of buildfarm animals don't support locales used in our
tests.  I've to revert that,

------
Regards,
Alexander Korotkov
Supabase