Martijn van Oosterhout wrote: > On Jan 5, 2008 7:06 PM, Sebastian Spaeth <[EMAIL PROTECTED]> wrote: >>> - When the server has the list of blank tiles to insert, it could run >>> one pass over the list to see if it's mostly sea of mostly land and >>> whatever it is, insert a blank tile with that type at zoom-12 and then >>> only insert the other types. >> Yes it could do that. My idea was to not take that hit at each insert, >> but rather run a cleanup script periodically that does these kinds of >> optimizations with lower priority. Once a z12 tile is marked as blank >> land/sea by such a script subsequent blankness entries at higher zoom >> levels become noop's. > > Sure, but it also cuts the number of insert to be done in the first > place, which produces a measurable speed improvement.
Which is good, I concur. > I actually have a script which grabs all the data for a given set of > zoom levels and actually calculates the minimum number of blank-tile > entries needed to represent that. It produces rather spectacular > results (>90% removal of entries). It's just complex enough that I've > left it for a few days so I when I look at it again I can recheck the > assumptions, but I'm pretty sure it works. Would be great if you could check that in if you are sure that it works. There is a trade off between the number of entries and the number of look-ups required. Do we wan to remove all unneccessary entries or do we want to keep all, say, z12 entries to make z17 lookups not too slow? > The way it's setup is a sort of daemon that monitors for newly > uploaded tilesets and optimises them straight away. It's quite quick > so eventually I'll probably run it over the entire DB and see how it > goes. If you're interested I can check it into SVN, maybe you can > check it for bugs... would be good. let me know if and where you check it in. spaetz _______________________________________________ Tilesathome mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/tilesathome
