I’m trying to do a location-based search on App Engine, but since the data store doesn’t support multiple inequality operators, I can’t search “where lat between a and b and lon between c and d”.
One of the solutions is to pre-compute bounding boxes to search on, as explained here:
http://code.google.com/appengine/articles/geosearch.html
However, I’m a little confused about “slices”. I’m trying to figure out:
- Why have slices? Why not just increase the resolution? Don’t they do the same thing?
-
Why does the same have 5 configs – won’t one do?
GEOBOX_CONFIGS = (
(4, 5, True),
(3, 2, True),
(3, 8, False),
(3, 16, False),
(2, 5, False),
)
I’m trying to figure out what to set the config to for my own app, but there are so many variables, it’s not clear what to do. Do I increase the resolution (first number), the number of slices (second number), add/remove config?
Ultimately, I’m interested in points within 10-15 miles (the code already sorts them by distance), but I don’t understand why it can’t be done with 1 config and the resolution set high enough.
I found another example which seems to wrap everything up nicely, and I don’t need to worry about all those crazy config values!
http://code.google.com/p/geomodel/wiki/Usage