jerha202 wrote: > > When setting a rectangle covering 709 objects, it takes 11 seconds to > loop through them. When using a rectangle covering 66 objects, it > takes 8 seconds. Unfortunately, this is insufficient for our > purposes. Does anyone else have experience of spatial query > performance issues, particularly on Windows CE? Any ideas of what we > could try to get better results? What should be the computational > time complexity with regard to the number of objects in the rectangle > and the total number of objects? >
That's an awful amount of time for such a small resultset. How much time does the same query take on a PC? It should be only a fraction of a second. I not familiar with the limitations of the filesystem of a pocket PC, so all I can say is that when a spatial filter is used, then the internal R-tree spatial index is used to fetch the features of interest. This could reault in lots of random disk access, i.e. multiple blocks of 512 bytes being read from random locations in the file... if the pocket PC OS is not efficient with fseek's in binary files then that could possibly explain the poor performance. Actually, given the structure of the TAB files (mainly the .MAP file) which is organized by 512 bytes blocks and that requires multiple blocks to be read for any given feature, even reading without a spatial filter could result in lots of fseek's and also result in poor performance if that is the problem. Daniel -- Daniel Morissette http://www.mapgears.com/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/mitab/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/mitab/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
