Horton

Re: Hybrid Hash/Nested Loop joins and caching results from subplans

Alvaro Herrera <alvherre@2ndquadrant.com>

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From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2020-09-02T13:49:54Z
Lists: pgsql-hackers 
On 2020-Sep-02, David Rowley wrote:

> v7 (Separate Result Cache node)
> Query 1:
>  Execution Time: 894.003 ms
> 
> Query 2:
>  Execution Time: 854.950 ms

> v7 + hacks_V3 (caching done in Nested Loop)
> Query 1:
>  Execution Time: 770.470 ms
>
> Query 2
>  Execution Time: 779.181 ms

Wow, this is a *significant* change.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Add Result Cache executor node (take 2)

  2. Add Result Cache executor node

  3. Allow estimate_num_groups() to pass back further details about the estimation

  4. Allow users of simplehash.h to perform direct deletions

  5. Cache if PathTarget and RestrictInfos contain volatile functions

  6. Fix pull_varnos' miscomputation of relids set for a PlaceHolderVar.