Re: BUG #19633: Unexpected results of IN (subquery) with a non-deterministic collation

From: Andrey Rachitskiy <pl0h0yp1(at)gmail(dot)com>
To: Richard Guo <guofenglinux(at)gmail(dot)com>
Cc: Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Tender Wang <tndrwang(at)gmail(dot)com>, syzhong16(at)gmail(dot)com, pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: BUG #19633: Unexpected results of IN (subquery) with a non-deterministic collation
Date: 2026-09-10 07:56:47
Message-ID: CAB8bMito5933gwme=3Z06-aeQeK7-DuvCRfQ6ZzO9VyfDvY32w@mail.gmail.com
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On backpatch the C change applies cleanly through 14. The regress
SQL hunks also apply, but the EXPLAIN text is not identical across
branches even when the counts are. I checked REL_19 through REL_14
with --with-icu. After the fix the counts are 1/1/1 and 3 everywhere.
The EXPLAIN differences are:

- Unique Sort Key on REL_18 and older prints
((test2cs.x)::text) COLLATE case_insensitive
where master/REL_19 print test2cs.x COLLATE case_insensitive

- unique-index case on REL_17 through REL_14 comes out as
Hash Semi Join rather than Hash Right Semi Join

So the backpatch will need a small expected.

--
Regards,
Rachitskiy Andrey

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