Re: GiST penalty functions [PoC]

> This thread has basically died, so marking as returned with feedback.
Well, not exactly died, but it's kind of in blind lead.

I'll summarize a bit for future references:
1. cube extension for indexing lowered dimensionality data (2d in 3d)
is broken. Queries effectively will degrade to full index scan.
2. In existing GiST API this can be fixed only with technique,
implemented in this patch. But this technique seems controversial.
3. This patch also brings 30%-40% speedup, but expected speedup of
advanced GIST API techniques is much higher.
As Norbert Beckmann put it in other discussion:
> Overlap optimization [requires API advancement] is one of the main elements, if not the main query performance tuning element of the RR*-tree. You would fall back to old R-Tree times if that would be left off.

Outcome: I'm planning to rollout another patch for both GiST and cube,
probably to next CF, which will render this patch unnecessary.
Thanks to everyone for discussion.

Best regards, Andrey Borodin.