| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Cc: | Michael Lewis <mlewis(at)entrata(dot)com>, Israel Brewster <ijbrewster(at)alaska(dot)edu>, PostgreSQL Mailing Lists <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Faster distinct query? |
| Date: | 2021-09-23 01:31:36 |
| Message-ID: | CAApHDvrecZLXdWNE00cb1bDAWO7jFDjJDoAToDAOZfMUyEuH5A@mail.gmail.com |
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| Lists: | pgsql-general |
On Thu, 23 Sept 2021 at 13:28, David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
> Agreed, though if the query author needs to do that here we’ve violated the spirit of the declarative SQL language. At first blush nothing about the original query seems like it should be preventing parallelism. Each worker builds its own distinct array then the final concatenation is made distinct.
We don't parallelise DISTINCT / ORDER BY aggregates.
David
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