Re: Have the planner convert COUNT(1) / COUNT(not_null_col) to COUNT(*)

David Rowley <dgrowleyml@gmail.com>

From: David Rowley <dgrowleyml@gmail.com>
To: Corey Huinker <corey.huinker@gmail.com>
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2025-11-03T22:49:15Z
Lists: pgsql-hackers
On Sat, 1 Nov 2025 at 14:19, Corey Huinker <corey.huinker@gmail.com> wrote:
>>
>> which might be a more realistic thing if the query without the WHERE
>> clause was part of a VIEW. However, we don't currently have any
>> infrastructure to detect when a column *is* NULL. There's only the
>> opposite with expr_is_nonnullable() or var_is_nonnullable().
>
> But we'd still catch NULL constants, yes?

Yes. It could. I've left that part of the patch #ifdef'd out. I wasn't
planning on using it. I just left it there as an example for if
someone wanted to test it.

>  The change is a big win for clarity. Applies clean. Passes.

Thanks for checking.

David



Commits

  1. Have the planner replace COUNT(ANY) with COUNT(*), when possible