The problem with using geohashes is that you can’t efficiently do ranges with random token distribution. So even if your scalar values are close to each other numerically they’ll likely end up on different nodes, and you end up doing a scatter gather.
If the goal is to provide a scalable solution, building a table that functions as an R-Tree or Quad Tree is the only way I know that can solve the problem without scanning the entire cluster. Jon > On May 9, 2017, at 10:11 AM, Jim Ancona <j...@anconafamily.com> wrote: > > There are clever ways to encode coordinates into a single scalar value where > points that are close on a surface are also close in value, making queries > efficient. Examples are Geohash <https://en.wikipedia.org/wiki/Geohash> and > Google's S2 > <https://docs.google.com/presentation/d/1Hl4KapfAENAOf4gv-pSngKwvS_jwNVHRPZTTDzXXn6Q/view#slide=id.i0>. > As Jon mentions, this puts more work on the client, but might give you a lot > of querying flexibility when using Cassandra. > > Jim > > On Mon, May 8, 2017 at 11:13 PM, Jon Haddad <jonathan.had...@gmail.com > <mailto:jonathan.had...@gmail.com>> wrote: > It gets a little tricky when you try to add in the coordinates to the > clustering key if you want to do operations that are more complex. For > instance, finding all the elements within a radius of point (x,y) isn’t > particularly fun with Cassandra. I recommend moving that logic into the > application. > > > On May 8, 2017, at 10:06 PM, kurt greaves <k...@instaclustr.com > > <mailto:k...@instaclustr.com>> wrote: > > > > Note that will not give you the desired range queries of 0 >= x <= 1 and 0 > > >= y <= 1. > > > > > > Something akin to Jon's solution could give you those range queries if you > > made the x and y components part of the clustering key. > > > > For example, a space of (1,1) could contain all x,y coordinates where x and > > y are > 0 and <= 1. You would then have a table like: > > > > CREATE TABLE geospatial ( > > space text, > > x double, > > y double, > > item text, > > m1, > > m2, > > m3, > > primary key ((space), x, y, m1, m2, m3, m4, m5) > > ); > > > > A query of select * where space = '1,1' and x <1 and x >0.5 and y< 0.2 and > > y>0.1; should yield all x and y pairs and their distinct metadata. Or > > something like that anyway. > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org > <mailto:user-unsubscr...@cassandra.apache.org> > For additional commands, e-mail: user-h...@cassandra.apache.org > <mailto:user-h...@cassandra.apache.org> > >
