Re: GIST optimization to limit calls to operator on sub nodes

Pujol Mathieu <mathieu(dot)pujol(at)realfusio(dot)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.