Date: Wed, 19 Oct 2016 13:04:16 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>,
	Alexander Korotkov <a.korotkov@postgrespro.ru>,
	Robert Haas <robertmhaas@gmail.com>,
	Alvaro Herrera <alvherre@2ndquadrant.com>,
	Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Indirect indexes
Message-ID: <20161019170416.GR5087@momjian.us>
References: <20161018182843.xczrxsa2yd47pnru@alvherre.pgsql>
 <CA+TgmoajGNsjTg7B3KjdpuDEuaOiMXWoh6ewc9jkhuCuv2deFQ@mail.gmail.com>
 <CAPpHfdseka0Vmukp9SRKgGDdGb7pYDcn-iWGqFv1a0R9em2anQ@mail.gmail.com>
 <CABOikdM2FpKs813oxfCXeAYR5SiK8V9-x8o7Y1zZpD_-Oso7BQ@mail.gmail.com>
 <20161019164043.GN5087@momjian.us>
 <CANP8+j+ERoVPn6gFevWqm6U=SGAeg3JhCASpLDLysKnUeViujg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: 
 <CANP8+j+ERoVPn6gFevWqm6U=SGAeg3JhCASpLDLysKnUeViujg@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

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.

> What we should ask is what is the difference between indirect indexes
> and WARM and to what extent they overlap.
> 
> My current understanding is that WARM won't help you if you update
> parts of a JSON document and/or use GIN indexes, but is effective
> without needing to add a new index type and will be faster for
> retrieval than indirect indexes.
> 
> So everybody please chirp in with benefits or comparisons.

I am not sure we have even explored all the limits of WARM with btree
indexes --- I haven't heard anyone talk about non-btree indexes yet.

-- 
  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 +


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers