From: Bruce Momjian <bruce@momjian.us>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: Alexander Korotkov <a.korotkov@postgrespro.ru>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Indirect indexes
Date: Thu, 20 Oct 2016 08:29:37 -0400
Message-ID: <20161020122937.GA28621@momjian.us> (raw)
In-Reply-To: <20161019170416.GR5087@momjian.us>
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On Wed, Oct 19, 2016 at 01:04:16PM -0400, Bruce Momjian wrote:
> On Wed, Oct 19, 2016 at 06:58:05PM +0200, Simon Riggs wrote:
> > >> I agree. Also, I think the recheck mechanism will have to be something like
> > >> what I wrote for WARM i.e. only checking for index quals won't be enough and we
> > >> would actually need to verify that the heap tuple satisfies the key in the
> > >> indirect index.
> > >
> > > I personally would like to see how far we get with WARM before adding
> > > this feature that requires a DBA to evaluate and enable it.
> >
> > Assuming WARM is accepted, that *might* be fine.
>
> First, I love WARM because everyone gets the benefits by default. For
> example, a feature that improves performance by 10% but is only used by
> 1% of users has a usefulness of 0.1% --- at least that is how I think of
> it.
Just to clarify, if a feature improves performance by 1%, but is enabled
by default, that is 10x more useful across our entire user base as the
feature numbers listed above, 1% vs 0.1%.
Also, it seems indirect indexes would be useful for indexing columns
that are not updated frequently on tables that are updated frequently,
and whose primary key is not updated frequently. That's quite a logic
problem for users to understand.
Also, if vacuum is difficult for indirect indexes, and also for WARM,
perhaps the vacuum problem can be solved for WARM and WARM can be used
in this case too.
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
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To: pgsql-hackers@postgresql.org
Cc: bruce@momjian.us, simon@2ndquadrant.com, pavan.deolasee@gmail.com, a.korotkov@postgrespro.ru, robertmhaas@gmail.com, alvherre@2ndquadrant.com
Subject: Re: Indirect indexes
In-Reply-To: <20161020122937.GA28621@momjian.us>
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