Re: Parallel Apply

From: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
To: "Zhijie Hou (Fujitsu)" <houzj(dot)fnst(at)fujitsu(dot)com>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, 'Amit Kapila' <amit(dot)kapila16(at)gmail(dot)com>, Tomas Vondra <tomas(at)vondra(dot)me>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Andrei Lepikhov <lepihov(at)gmail(dot)com>, wenhui qiu <qiuwenhuifx(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Parallel Apply
Date: 2026-04-17 05:48:12
Message-ID: aeHIVhNiFtfGss4b@alvherre.pgsql
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Hello,

I have a quick question about this work -- is there an expectation of
how quicker parallel apply is, compared to our normal (serial) apply,
for average cases? Are we talking 20% faster, 2x faster, 10x faster?

(When I say average, I mean not considering fringe cases where the
workload is such that very little paralelization can be done, and also
those where you have a contrived case with one thousand parallel
processes each making progress separately to the point where you get
ridiculously high numbers. I mean something that can occur in realistic
workloads.)

My point is that if it's 20% faster, it's nice. But if it's, say, 4x
faster, then it's probably groundbreaking to the point that it may
enable new use cases not currently possible.

Thoughts, pointers?

Many thanks

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"¿Qué importan los años? Lo que realmente importa es comprobar que
a fin de cuentas la mejor edad de la vida es estar vivo" (Mafalda)

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