| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Sergey Shinderuk <s(dot)shinderuk(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, David Rowley <drowley(at)postgresql(dot)org> |
| Subject: | Re: Bug in row_number() optimization |
| Date: | 2022-11-25 03:00:27 |
| Message-ID: | CAMbWs4-8UnEWbb8t-mqD0oSSUF_6eK7++BkzaEED8kCvN7g90Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Nov 25, 2022 at 7:34 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> Since upper-level WindowAggs cannot reference values calculated in
> some lower-level WindowAgg, why can't we just NULLify the pointers
> instead? See attached.
Verified the problem is fixed with this patch. I'm not familiar with
the WindowAgg execution codes. As far as I understand, this patch works
because we set ecxt_aggnulls to true, making it a NULL value. And the
top-level WindowAgg node's "Filter" is strict so that it can filter out
all the tuples that don't match the intermediate WindowAgg node's run
condition. So I find the comments about "WindowAggs above us cannot
reference the result of another WindowAgg" confusing. But maybe I'm
missing something.
Thanks
Richard
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