[OSM-talk] Bounding box

[Raphaël Jacquot]

Nick Hill wrote:

> Mysql implements partitioning which is transparent to the queries or API.

hmm, ok.

> Unless the partitioning is extremely fine-grained, few bounding boxes 
> will cross the border between partitions.

I supposed that at some point you'd need to increase the fine-ness of 
the partitionning, no ?

> I agree you didn't mention OGC, but given you didn't specifically tell 
> me what you *were* referring to, and given you alluded to the nature of 
> an inflated size  index, I think most people would forgive me for 
> concluding that is what is in your mind.

well, it's similar to precalculation of extremely large tables in 
cryptoanalysis to help make it realtime.

>> the box limit requirement is a function of the time it takes for
>> a) the database to return the resultset
>> b) the time it takes for the web server to format that resultset to xml
>> c) some value dependant on whatever scripting language used
> 
> z)You can also add to that things like: Tendency for a query to flush 
> other used data from a cache

that's where you need more ram, so that the *indexes* end up in there.
(that's where things like http://www.superssd.com/products/tera-ramsan/ 
of which the largest installation sits somewhere within NSA, are used)

> y) I/O taken to retrieve perhaps hundreds of millions of data points, 
> sort them, find duplicates, return whatever page

it's the query optimizer job to order the bits composing the request so 
that the heavy operations are executed on limited data sets.

> If we used a more efficient indexing scheme, the database may perhaps 
> more easily determine the implication of the request from bounding box 
> information.
> 
> To perform tests, get the mysql schema from SVN. Load it into mysql. Get 
> the planet dump then use planet2mysql to generate the OSM dataset in mysql.
> 
> Download the API from SVN. Point the API at the database. Run queries. 
> Make changes to the database. Find some fabulous new way of increasing 
> the speed with unlimited bounding boxes and no server slowdown. give us 
> all the figures. Convince everyone. I'll buy you a pint.

that's understandable, but is not representative, as the planet doesn't 
have any history information.