[OSM-talk] OGL, OSM, NASA

Raphaël Jacquot sxpert at esitcom.org
Wed Apr 26 11:52:55 BST 2006


Nick Hill wrote:

> Questions:
> 1) Do geometric R-tree type indexes need 2, 4 or 8 indexed values per 
> point?
> 
> 2) Do geometric R-tree indexes grow in a non-linear fashion with number 
> of indexed rows?
> 
> 3) Does the R-tree indexing time for new points necessarily grow in a 
> non-linear fashion with number of indexed rows?
> 
> 4) If the R-tree can't fit in memory, is there an R-tree implementation 
> which can substantially cut down the number of disc seeks?

the source to the GIST implementation lives here :
http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/

standard data types are here:
http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/

> 5) Are there any other relevant questions to using R-trees? If we get 
> positive answers to the above questions, we need to re-run tests in the 
> light of those answers to check this.
> 
> We than need to compare the results to the possible optimisations we can 
> make to b-trees.

r-trees have been specifically designed for 2D things...

> This way, we can save a lot of work for others by mathematically 
> establishing the design decisions we must offset for the open streetmap 
> database.






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