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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Benjamin Tingle <ben@tingle.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: Query Planner not taking advantage of HASH PARTITION
Date: Sun, 17 Apr 2022 20:50:14 +0200
Message-ID: <202204171850.iqpjc2mmr47y@alvherre.pgsql> (raw)
In-Reply-To: <CABTcpyvoSYrn-2S4p8hRwAsCe3PkOUS4dFxmr6gUy4x9u5PDKA@mail.gmail.com>

On 2022-Apr-14, Benjamin Tingle wrote:

> It doesn't help if I partition temp_data by textfield beforehand either
> (using the same scheme as the target table). It still opts to concatenate
> all of temp_data, hash it, then perform a sequential scan against the
> target partitions.

Does it still do that if you set
  SET enable_partitionwise_join TO on;
?  If the partition strategies are identical, that might get you a
better plan.  (Actually, in pg13 and upwards the strategies don't need
to be exactly identical, just "compatible".)

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end." (2nd Commandment for C programmers)





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