"jorge alberto" <jorge.is.a.geek@gmail.com> writes:
> where can i find the .h that describes the interface that a spatial access
> method, like the R-tree, must have in order to work with postgresql.
There is no single .h file that will tell you everything you need to know.
I'd suggest starting here:
http://developer.postgresql.org/pgdocs/postgres/internals.html
with particular attention to chapter 48
http://developer.postgresql.org/pgdocs/postgres/indexam.html
After that the indexam README files might be educational:
src/backend/access/nbtree/README
src/backend/access/gin/README
src/backend/access/gist/README
src/backend/access/hash/README
and then start looking at .h files.
regards, tom lane