Re: parse partition strategy string in gram.y

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: "Finnerty, Jim" <jfinnert(at)amazon(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Japin Li <japinli(at)hotmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: parse partition strategy string in gram.y
Date: 2022-10-25 23:23:36
Message-ID: 20221025232336.6zisdii6n6sbdacq@alvherre.pgsql
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On 2022-Oct-26, Alvaro Herrera wrote:

> On 2022-Oct-25, Finnerty, Jim wrote:
>
> > Or if you know the frequencies of the highly frequent values of the
> > partitioning key at the time the partition bounds are defined, you
> > could define hash ranges that contain approximately the same number of
> > rows in each partition. A parallel sequential scan of all partitions
> > would then perform better because data skew is minimized.
>
> This sounds very much like list partitioning to me.

... or maybe you mean "if the value is X then use this specific
partition, otherwise use hash partitioning". It's a bit like
multi-level partitioning, but not really.

(You could test this idea by using two levels, list partitioning on top
with a default partition which is in turn partitioned by hash; but this
is unlikely to work well for large scale in practice. Or does it?)

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Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
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