Peter, Thanks for the suggestion but that's not the part I'm trying to optimise at the moment. It could be useful to use auxdata there as well to avoid reparsing the text of course. What I would really like to achieve is that the GEOSPreparedGeometry can be cached to speed up the geometry calculations.
Pepijn On 07 Sep 2013, at 00:58, Peter Aronson <pbaron...@att.net> wrote: > Actually, as it turns out, you can get the result you want by having the > GeomFromText function use auxdata to store the geometry blob generated from > the WKT string, since it's a constant. Then all the GeomFromText has to do > is to return the Geometry blob when sqlite3_get_auxdata returns non-NULL. > > Peter > > ----- Original Message ----- >> From: Pepijn Van Eeckhoudt <pep...@vaneeckhoudt.net> >> To: sqlite-users@sqlite.org >> Cc: >> Sent: Friday, September 6, 2013 8:38 AM >> Subject: [sqlite] How to use aux_data effectively? >> >> Hi, >> >> In the extension I'm developing (https://bitbucket.org/luciad/libgpkg) >> I'm currently adding support for queries like: >> select Distance( >> GeomFromText('Point(13.457 3)'), >> geometry >> ) from table; >> >> GeomFromText takes a string and outputs a geometry blob >> Distance takes two geometry blobs and returns a double >> >> In order to speed up the distance function I was wondering if I could >> use aux_data to cache the parsed version of the first parameter since >> this remains the same for every call. So far I haven't been able to get >> this to work though, aux_data is always NULL, no matter what I try. >> >> My hunch is that this is because the first parameter is the result of a >> function call which could in theory return different values for each row >> even if the input parameters are constant. Is that correct? >> >> Are there any other ways to kind of memoize the GeomFromText function >> (or the parameters to distance) besides aux_data? >> >> Thanks, >> >> Pepijn >> >> _______________________________________________ >> sqlite-users mailing list >> sqlite-users@sqlite.org >> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >> > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
