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From: Emre Hasegeli <emre@hasegeli.com>
To: Pujol Mathieu <mathieu.pujol@realfusio.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: GIST optimization to limit calls to operator on sub nodes
Date: Sun, 29 Jun 2014 23:14:19 +0300
Message-ID: <20140629201419.GA63570@hasegeli.local> (raw)
In-Reply-To: <53A7D547.5080302@realfusio.com>
References: <53A7D547.5080302@realfusio.com>
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Pujol Mathieu <mathieu.pujol@realfusio.com>:
> Hello,
> I already post my question in the General Mailing list, but without
> succeed so I try this one that seems to me more specialized.
> My question is about GIST index.
> 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.


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