[OSM-dev] How to keep a geographic local part of OSM updated with minutely diffs?

[tb]

Hi,

i'm running a local database of the OpenStreetMap data, and this 
database is permanently updated by using osmosis and osm2pgsql (minutely 
diffs).

Now i'm interested in keeping just a region like a city or a small state 
updated the same way (on a much smaller system). The region i'm 
interested in is defined as a polygon in a separate table, and i keep 
the content of all the mapnik tables (planet_osm_point, ...line, 
...polygon, ...roads) to this region by using a trigger - no problem so 
far. But unfortunately the other tables used by osm2pgsql 
(planet_osm_nodes, ...ways, ...rels) getting bigger by time.

Complete reload of the region every night is something i don't like - so 
far.

I wonder if someone has a system like this up and running, and how this 
works.

Is this possible in general by using osm2pgsql?

Any help or suggestions gratefully accepted!
-tb