[OSM-dev] OSM and MongoDB

[Frederik Ramm]

Hi,

On 04/12/2011 02:58 AM, Ian Dees wrote:
> The most recent dev version of MongoDB includes "multi-location
> documents" support:
> http://www.mongodb.org/display/DOCS/Geospatial+Indexing#GeospatialIndexing-MultilocationDocuments
>
> This would allow a single way document to be indexed at multiple
> locations and vastly speed up the map query.

It sounds to me that if one were to make extensive use of that feature, 
one would basically recreate the whole OSM database inside MongoDB's 
index structure. Before too long, you'll end up storing only "empty 
documents" because all the data you need has been migrated to the index 
in order to achieve decent performance ;)

What's more, a linear object, in theory, has an infinite number of 
"locations"; without knowing the inner workings of MongoDB I must assume 
that choosing only a few of them for inclusion in the index might lead 
to the object being falsely omitted from some query results (just as we 
have it today when we only search for nodes inside a bounding box and 
thereby miss ways that intersect our box without having a node inside).

Bye
Frederik