From: Tom Lane <tgl@sss.pgh.pa.us>
To: Emre Hasegeli <emre@hasegeli.com>
cc: Pujol Mathieu <mathieu.pujol@realfusio.com>,
 PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: GIST optimization to limit calls to operator on sub nodes
In-reply-to: <20140629201419.GA63570@hasegeli.local>
References: <53A7D547.5080302@realfusio.com>
 <20140629201419.GA63570@hasegeli.local>
Comments: In-reply-to Emre Hasegeli <emre@hasegeli.com>
 message dated "Sun, 29 Jun 2014 23:14:19 +0300"
Date: Sun, 29 Jun 2014 16:30:22 -0400
Message-ID: <4113.1404073822@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-performance-owner@postgresql.org

Emre Hasegeli <emre@hasegeli.com> writes:
> Pujol Mathieu <mathieu.pujol@realfusio.com>:
>> I made my own index to handle specific data and operators. It works
>> pretty fine but I wonder if it was possible to optimize it.
>> When I run my operator on a GIST node (in the method
>> gist_range_consistent) it returns "NotConsistent" /
>> "MaybeConsistent" / "FullyConsistent".
>> NotConsistent -> means that all subnodes could be ignored,
>> gist_range_consistent return false
>> MaybeConsistent -> means that at least one subnode/leaf will be
>> consistent, gist_range_consistent return true
>> FullyConsistent -> means that all subnodes/leaves will be
>> consistent, gist_range_consistent return true
>> 
>> So like with the "recheck flag" I would like to know if there is a
>> way to notify postgres that it is not necessary to rerun my operator
>> on subnodes, to speedup the search.

> I do not think it is possible at the moment.  The GiST framework can
> be extended to support this use case.  I am not sure about the
> speedup.  Most of the consistent functions do not seem very expensive
> compared to other operations of the GiST framework.  I would be
> happy to test it, if you would implement.

I don't actually understand what's being requested here that the
NotConsistent case doesn't already cover.

			regards, tom lane


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