today i was rolling out some new search functionality and really needed the ‘geoNear’ functionality of mongo
http://docs.mongodb.org/manual/reference/command/geoNear/
unfortunately the mongoid (3) gem doesn’t directly support it.
fortunately durran’s (https://twitter.com/modetojoy) code is tight enough that a few moments of digging found the solution, and led to this actual code:
# http://stackoverflow.com/questions/5319988/how-is-maxdistance-measured-in-mongodb
# 1° latitude = 69.047 miles = 111.12 kilometers
#
DEGREES_PER_MILE = 1 / 69.047
MILES_PER_DEGREE = 1 / DEGREES_PER_MILE
def Store.find_all_by_lat_lng(lat, lng, options = {})
options.to_options!
miles = options[:miles] || 100
max_distance = miles * DEGREES_PER_MILE
doc =
Mongoid.session(:default).
command(
:geoNear => Store.collection_name,
:near => {:lat => lat, :lng => lng},
:maxDistance => max_distance
)
stores = []
if doc['ok'] == 1.0
results = Array(doc['results'])
results.each do |result|
distance_in_degrees = result['dis']
obj = result['obj']
store = Store.instantiate(obj)
store['distance'] = Float(distance_in_degrees) * MILES_PER_DEGREE
stores.push(store)
end
end
stores
end