Christophe Rousson ha scritto: > Hi Ian and Andrea, > > I wrote down my plan for using a quadtree to cache features : > > http://docs.codehaus.org/display/GEOTOOLS/SoC+2007+Caching+data#SoC2007Cachingdata-ideasquadtree > > <http://docs.codehaus.org/display/GEOTOOLS/SoC+2007+Caching+data#SoC2007Cachingdata-ideasquadtree> > > Could you have a look at this ?
I looked at the description, did not have enough time for the code sorry. The idea looks good, I have a few questions thought: * does a non leaf tile contain geometries? If not, where do you put geometries that cover more than one tile? What if your map has shorelines or isolines that span most of the map? * what do you do if there are many partial nodes under the same node, that is, if the situation is not clear cut? Do a lot of queries? At a certain level you should stop and reload a few of the features in order to execute less queries, since query setup and latency have a price too. * This somehow has consequences on eviction... a good eviction policy will try to keep the holes in the tree big and square instead of generating a crossword like picture * I think eviction search should not be that expensive if you are able to keep the tree relatively small (level wise) and you update the last updated time from the leaf up to the root for each access. It would also be interesting to have an estimate of how many megabytes of stuff are there under each node (down to the leaves) so that you can decide where you have enough stuff to evict to gather back the space you need to load the missing parts * when a query has only partial match, I guess you should first lock the nodes that answer part of the query (minus those that you may reload due to query grouping) and then evict those that are not locked. Ok, that's enough for the moment. Keep up the good work Cheers Andrea ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Geotools-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-devel
