Re: Creating Empty Index

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, "naman(dot)iitb" <naman(dot)bbps(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Creating Empty Index
Date: 2013-11-03 03:01:07
Message-ID: 22979.1383447667@sss.pgh.pa.us
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Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
> On Sat, Nov 2, 2013 at 10:28 PM, Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
>> What exactly would be the point? Indexes are automatically maintained by
>> postgres. Something that isn't doesn't seem to me to qualify for the
>> description of "index".

> Perhaps an index without data that could be used by the planner for
> automatic query tuning to evaluate how a query could run if the index
> exists? Like the concept of hypothetical indexes or something like the
> possibility to do a CREATE/ALTER INDEX ... WITH [ NO ] DATA.

But we already provide support for hypothetical indexes via planner
plugins. Why would you need an actual empty index underlying that?

I agree with Andrew that the use-case for this hasn't been explained.

regards, tom lane

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