| From: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Alexander Alexander <alexander(dot)berezin3000(at)gmail(dot)com>, pgsql-bugs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: BUG #18477: A specific SQL query with "ORDER BY ... NULLS FIRST" is performing poorly if an ordering column is n |
| Date: | 2024-06-06 08:10:53 |
| Message-ID: | 8807644dd252993a498b4ec77e6ecbc46808b142.camel@cybertec.at |
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| Lists: | pgsql-bugs |
On Thu, 2024-06-06 at 17:04 +1200, David Rowley wrote:
> On Thu, 6 Jun 2024 at 15:48, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > AFAICS the problem is purely self-inflicted damage: why is the user
> > specifying NULLS FIRST if he knows the column is not-null?
>
> If the user has some genuine reason for creating a NULLS FIRST index
> for some other query, then it might be nice if we were able to use
> that index for Merge Joins instead of them having to create another
> index to speed up the join query.
I cannot imagine a genuine reason for creating a NULLS FIRST index
on a NOT NULL column, but perhaps I am too narrow-minded.
Yours,
Laurenz Albe
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