| From: | Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Amit Langote <amitlangote09(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, tomas(at)vondra(dot)me, vignesh C <vignesh21(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Richard Guo <guofenglinux(at)gmail(dot)com> |
| Subject: | Re: Reducing memory consumed by RestrictInfo list translations in partitionwise join planning |
| Date: | 2025-03-28 16:46:15 |
| Message-ID: | CAExHW5ufwK=7UgegeQVVjewiZqGaY6CsA+5ht1OpO_yS0EkHBQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Mar 28, 2025 at 12:01 PM Ashutosh Bapat
<ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
>
> Comparing root->join_rel_hash with EC->ec_derives_hash in the context
> of initial hash table size is a thinko on my part. It's less likely
> that there will be 1000 subqueries (requiring 1000 PlannerInfos) each
> with more than 32 join rels than a query with 1000 equivalence classes
> in one PlannerInfo with more than 32 ec_derives. So if using a small
> initial hash table doesn't impact performance negatively, why not save
> some memory. Thinking more about it, we know the size of
> ec_derives_list when creating the hash table and we are using
> simplehash which uses its own fillfactor and its own logic to expand
> the hash table, I think we should just use the length of
> ec_derives_list as the initial size. What do you think?
>
PFA patches. 0001 and 0002 are the same as the previous set. 0003
changes the initial hash table size to the length of ec_derives.
--
Best Wishes,
Ashutosh Bapat
| Attachment | Content-Type | Size |
|---|---|---|
| 0001-Add-assertion-to-verify-derived-clause-has--20250328.patch | text/x-patch | 1.5 KB |
| 0002-Make-derived-clause-lookup-in-EquivalenceCl-20250328.patch | text/x-patch | 25.5 KB |
| 0003-Use-length-of-ec_derives-clause-list-as-ini-20250328.patch | text/x-patch | 1.1 KB |
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