[osmosis-dev] postGIS: bbox columns?

[Frederik Ramm]

David,

David Carmean wrote:
> 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 probably have not made myself clear enough. It is obvious that having 
a proper linestring in your table, together with a GIST index, beats 
having just a bbox, and it is unlikely that any application will be 
unable to make use of the index.

HOWEVER, it takes much longer to import the full linestrings than to 
just import a bbox in the first place.

So if your application, for whatever reason, does not need pre-built 
geometries, but just an overall idea of where in the world a certain way 
is, then the bbox builder mechanism in Osmosis allows you to skip 
linestring generation altogether, saving time and storage space.

The bbox column does not present added value if you intend to import the 
full linestrings. It is only useful if you want a lean database without 
full linestrings.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"