Accessing the internal data structure storing Postgis spatial index (PostGres GiST)

Question

I am curious about how the internal data structures and storage mechanism of the spatial GiST index in Postgis. In Oracle, I used to like to show how the SDO indexes were "just another table", and how the levels were attributes of the indexes, and the bboxes of the indexed geometries were stored as blobs (that could be extracted). HOw does postgis store the indexes, and where?

The system tables http://www.postgresql.org/docs/8.3/static/catalogs.html can be used to identify indexes, but I do not know how to access the actual storage ( if they are indeed tables)

Answer 1

As Craig mentions the spatial indexes are not just another table. Instead, PostGis uses GiST as the structural foundation for storing bbox details. Yes, this is (when using defaults) different and more efficient and less precise that B-Trees, or R-Trees....but you can specify parameters which make GiST indexes similar to spatial indexes from other storage.

Here is the documentation on how to work with them (including extending them.)

Dig in.