| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Ronan Dunklau <ronan(dot)dunklau(at)aiven(dot)io>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Pavel Luzanov <p(dot)luzanov(at)postgrespro(dot)ru>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
| Subject: | Re: Add proper planner support for ORDER BY / DISTINCT aggregates |
| Date: | 2022-11-08 06:51:00 |
| Message-ID: | CAMbWs4_+5cP+8xjiAc=hds935ZiiG6oepPDeVNovWhQ66DARJw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Nov 8, 2022 at 9:31 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> I've been playing around with the attached patch which does:
>
> 1. Adjusts add_paths_to_grouping_rel so that we don't add a Sort path
> when we can add an Incremental Sort path instead. This removes quite a
> few redundant lines of code.
For unsorted paths, the original logic here is to explicitly add a Sort
path only for the cheapest-total path. This patch changes that and may
add a Sort path for other paths besides the cheapest-total path. I
think this may introduce in some unnecessary path candidates.
I think it's good that this patch removes redundant codes. ISTM we can
do the same when we try to finalize the partially aggregated paths from
partially_grouped_rel.
Thanks
Richard
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