Re: Proposal: Global Index

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Peter Geoghegan <pg(at)bowt(dot)ie>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, 曾文旌 <wenjing(dot)zwj(at)alibaba-inc(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Amit Langote <amitlangote09(at)gmail(dot)com>, Hamid Akhtar <hamid(dot)akhtar(at)gmail(dot)com>, "heikki(dot)linnakangas" <heikki(dot)linnakangas(at)iki(dot)fi>, "Nasby, Jim" <nasbyj(at)amazon(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Subject: Re: Proposal: Global Index
Date: 2021-01-11 20:24:06
Message-ID: 20210111202406.GL4320@momjian.us
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On Mon, Jan 11, 2021 at 12:05:43PM -0800, Peter Geoghegan wrote:
> On Mon, Jan 11, 2021 at 11:25 AM Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > Once you layer on all the places a global index will be worse than just
> > creating a single large table, or a partitioned table with an index per
> > child, there might not be much usefulness left. A POC patch might tell
> > us that, and might allow us to mark it as "not wanted".
>
> I'm confused. Of course it's true to some degree that having a global
> index "defeats the purpose" of having a partitioned table. But only to
> a degree. And for some users it will make the difference between using
> partitioning and not using partitioning -- they simply won't be able
> to tolerate not having it available (e.g. because of a requirement for
> a unique constraint that does not cover the partitioning key).

Yes, that is a good point. For those cases, I think we need to look at
the code complexity/overhead of supporting that feature. There are
going to be a few cases it is a win, but will the code complexity be
worth it?

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EnterpriseDB https://enterprisedb.com

The usefulness of a cup is in its emptiness, Bruce Lee

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