Horton

Re: [PATCH] ANALYZE: hash-accelerate MCV tracking for equality-only types

John Naylor <johncnaylorls@gmail.com>

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From: John Naylor <johncnaylorls@gmail.com>
To: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>
Cc: Chengpeng Yan <chengpeng_yan@outlook.com>, Tatsuya Kawata <kawatatatsuya0913@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2026-05-04T02:10:16Z
Lists: pgsql-hackers 
On Thu, Feb 26, 2026 at 6:46 PM Ilia Evdokimov
<ilya.evdokimov@tantorlabs.com> wrote:
> While reviewing the patch more closely, I noticed
> that compute_distinct_stats() is only used for types where we have =, !=
> but not <. In practice, most common scalar types go through
> compute_scalar_stats() instead.
>
> That makes me wonder how often this optimization would actually trigger
> in real workloads. Since compute_scalar_stats() is the more common path,
> there's chance that the hash-table based improvement in
> compute_distinct_stats() may not provide a noticeable overall benefit.

Coming back to this point, in any installation, the common path is
going to vastly outnumber the rare path, so this patch is optimizing
the wrong thing.

-- 
John Naylor
Amazon Web Services