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In-Reply-To: <119bd418-1d7a-42c7-9270-86f3b6696399@gmail.com>
From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Thu, 16 Apr 2026 10:58:40 -0700
Message-ID: <CAD21AoAit-Qp9OriVbb9c_Qebi=Cgxz0AQJu+zxQpp=_1Lt2dQ@mail.gmail.com>
Subject: Re: TRAP: failed Assert("offsets[i] > offsets[i - 1]"), File: "tidstore.c"
To: Andrei Lepikhov <lepihov@gmail.com>
Cc: PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
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On Thu, Apr 16, 2026 at 1:26=E2=80=AFAM Andrei Lepikhov <lepihov@gmail.com>=
 wrote:
>
> On 16/04/2026 10:11, Masahiko Sawada wrote:
> > On Thu, Apr 16, 2026 at 12:13=E2=80=AFAM Andrei Lepikhov <lepihov@gmail=
.com> wrote:
> > -- Random TIDs test. The offset numbers are randomized and must be --
> > unique and ordered. INSERT INTO hideblocks (blockno) SELECT
> > do_set_block_offsets(blkno, array_agg(DISTINCT greatest((random() *
> > :maxoffset)::int, 1))::int2[]) FROM generate_series(1, 100)
> > num_offsets, generate_series(1000, 1100, 1) blkno GROUP BY blkno;
>
> Alright, I used an explicit sort in reverse order to make sure the test i=
s
> stable. I usually create modules that may change different paths, costs, =
and
> orders, and using random can make things unpredictable. But for this spec=
ific
> test, I don't see any risk.
>
> >
> > While I agree that we need to sort the offset numbers, I think it
> > would be better to make sure the offset numbers in the array to be
> > sorted in a test_tidstore.sql file where required, instead of doing so
> > for all cases.
>
> I'm not sure I follow. Are you saying that do_set_block_offsets shouldn't=
 sort
> the incoming offsets?

No, I wanted to mean that if we sort the given array in
do_set_block_offsets() as the proposed patch does, we end up always
sorting arrays even if the sorting is no actually required (e.g., when
executing "SELECT do_set_block_offsets(1,
array[1,2,3,4,100]::int2[]);"). So an alternative idea to stabilize
the regression test would be to create a SQL function to return a list
of sorted offsets and use it where it's required. While the patch gets
a little bigger, It would also help simplify the tests somewhat by
removing the redundant codes. I've attached the patch for this idea.

Regards,

--=20
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

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