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From: David Rowley <dgrowleyml@gmail.com>
Date: Thu, 23 Apr 2026 17:32:43 +1200
Message-ID: 
 <CAApHDvrJMOReoQOOp-_bFAHH8NTbUPy5L-CwX5XQo_7m55YNMw@mail.gmail.com>
Subject: Re: [PATCH] Fix hashed ScalarArrayOp semantics for NULL LHS with
 non-strict comparators
To: Chengpeng Yan <chengpeng_yan@outlook.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>,
 cca5507 <cca5507@qq.com>,
	Tom Lane <tgl@sss.pgh.pa.us>
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Thanks for looking.

On Thu, 23 Apr 2026 at 16:31, Chengpeng Yan <chengpeng_yan@outlook.com> wrote:
> One possible improvement, though not
> a blocker, would be to defer the lhs-NULL handling until we actually
> encounter the first NULL on the lhs. That could avoid a bit of extra
> work in the common case where the lhs contains no NULLs.

I thought of it, but didn't do it as it meant having to keep a bit
more state to track if we've filled the cache yet, plus the extra
costs incurred to check if we've done it yet that would have to be
paid for every NULL lookup. We currently have to check if the hash
table has been set up already, so I felt more comfortable installing
the new code in with that.

David