| From: | John Naylor <john(dot)naylor(at)enterprisedb(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Time to increase hash_mem_multiplier default? |
| Date: | 2022-01-19 19:31:51 |
| Message-ID: | CAFBsxsHhf5Kw5xaGvva-Y9cmXnzD9w79wuUZDco4v-HDzx0LHg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, Jan 16, 2022 at 7:28 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
>
> The current hash_mem_multiplier default is 1.0, which is a fairly
> conservative default: it preserves the historic behavior, which is
> that hash-based executor nodes receive the same work_mem budget as
> sort-based nodes. I propose that the default be increased to 2.0 for
> Postgres 15.
I don't have anything really profound to say here, but in the last
year I did on a couple occasions recommend clients to raise
hash_mem_multiplier to 2.0 to fix performance problems.
During this cycle, we also got a small speedup in the external sorting
code. Also, if the "generation context" idea gets traction, that might
be another reason to consider differentiating the mem settings.
--
John Naylor
EDB: http://www.enterprisedb.com
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