[osmosis-dev] postGIS: bbox columns?

[David Carmean]

On Sun, May 23, 2010 at 12:23:27AM +0200, Frederik Ramm wrote:
> Hi,
> 
> David Carmean wrote:
> >     Who/what uses the ways.bbox column?  Is there something/somebody 
> >     that cannot use the linestring gist index, but instead requires 
> >     an explicit bounding box geometry?
> 
> Is the bbox column not meant to be a quicker alternative to a full 
> linestring (quicker in importing, not quicker in using)? I.e. you won't 
> have a linestring to base your GIST index on if you use that as intended.

The presence of the gist index on the linestring geometry column is what
allows the GIS client I use to link only a small portion of the dataset
based on a bounding box I specify; without it, it links the entire table
as a drawing layer.  The gist index presents a "proxy" bounding box 
internally.
 
  http://postgis.refractions.net/documentation/manual-1.3/ch03.html#id2570609

As described above, this index can be used to perform a quick first-pass 
query based on just the table indices (proxy bounding boxes) and present 
the main query with a pre-filtered set of candidates.  

I'm just wondering if there's some other application that uses this 
explicitly-built bbox geometry column (and whether it could be improved 
by using the index instead).