This sounds much simpler :-) Frederik Ramm wrote: > Hi, > > >> I think that adding the Lat/Lon tag to node references in the ways is not an >> option since it would require a huge amount of queries on the database when >> creating the diffs. The positive side of this would that it would only have >> to be done once. >> > > If you are happy with supporting only zoom level 16 granularity, you can > store the tile x and tile y coordinates for each node, that's only 4 > bytes per node. > > If you create a file that contains four bytes for every node, indexed > simply by node id (node #1 x at file position 0, node #1 y at 2, node #2 > x at 4 etc.), then your file will have about 1.2 Gig for the current > planet. When processing a diff you would simply mmap that file, > effectively loading into memory and granting very fast access to node > positions. > > This wastes some memory because it reserves space for deleted nodes as > well, but when I last looked the number of "deleted" node ids was about > 20%, and this is an acceptable overhead - otherwise you would have to > use something like a hashtable to index your node list which would use > more than that. > > Bye > Frederik > >
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