SP-GIST docs and examples

I know Oleg has been discussing quad trees for years now, so SP-GIST
sounds like a great feature.

The docs on SP-GIST simply suggest people read the code, which is way
below our normal standard of documentation.

CREATE INDEX contains no examples involving SP-GIST indexes.

It seems likely that the first thing a user will ask is When can I use
it? How do I create one? When should I use it in comparison with
existing methods?

ISTM that if we mention this as a major feature in 9.2, and I think we
should, that there should be something more about these in the shared
docs.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services