[Openstreetmap] graph reduction

[Raphaël Jacquot]

Immanuel Scholz wrote:

> This means, all nodes and all line segments in the given area need to be
> processed.
> 
> If the assumption is true, that bottleneck for delivering street
> information is the CPU power (or I/O capabilities) of the server and not
> the bandwidth, this is currently contra-productive.
> 
> If objects are tagged after importness, the amount of data to be processed
> (and transfered) can be reduced at SQL level.

a couple tricks than can be used

* do some of the things (like adding points/lines) as stored procedures 
instead of scripting multiple queries in a transaction from the web server
* using a 64bit machine with tons of ram (so that the db ends up in the 
buffer segments in ram)
* the above in turns needs a good UPS with a connection to the box to 
turn it off property at a moment's notice, and fairly often syncs
* furthermore, for this kind of application, the AMD 64 bit processors 
are better as they cut 1/2 the ram access latency that the comparable 
intels have (which in turns makes the app 2x faster)