Message-ID: <53A7D547.5080302@realfusio.com>
Date: Mon, 23 Jun 2014 09:20:39 +0200
From: Pujol Mathieu <mathieu.pujol@realfusio.com>
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To: pgsql-performance@postgresql.org
Subject: GIST optimization to limit calls to operator on sub nodes
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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.

For example, consider the following gist tree
           R
     /         \
    Na          Nb
  /   \       /    \
La1  La2    Lb1  Lb2

If all nodes return FullyConsistent, postgres will run tests in that 
Order : R, Na, Nb, La1, La2, Lb1, Lb2, thanks to recheck flag it will 
not test rows associated to leaves Lxx.
My goal is that postgres run test on R and then skip tests on other 
nodes. So is there a way to do that in the GIST API ? Or could I share 
data from R to Nx and then From Na to Lax and Nb to Lbx ?
Thanks,
Mathieu


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