| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Issue with query_is_distinct_for() and grouping sets |
| Date: | 2025-10-23 03:43:36 |
| Message-ID: | CAMbWs48-jA654k+UKZ-S2Pym1bcQQtMLxC=DAzKJGcL_yOE09w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Oct 23, 2025 at 12:07 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> Or if it's a case of it returning false when it could have returned
> true, then maybe the commit message should make that clear. I'm unable
> to tell from reading it. Something like; "The previous logic in
> query_is_distinct_for() was incomplete [as it failed to detect that a
> query was distinct when ...]".
It's the case of failing to recognize distinctness when it actually
holds (i.e., a false negative). Therefore, this issue does not cause
incorrect results, but rather leads to missed optimization
opportunities.
How about using the following wording in the commit message?
"
The previous logic in query_is_distinct_for() was incomplete because
the check was insufficiently thorough and could return false when it
should have returned true.
"
- Richard
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