redis_geohash

location-aware lists + simple distance calculation with geohashes and ruby/redis. geohash implementation in pure ruby.

http://en.wikipedia.org/wiki/Geohash

using redis_geohash

RedisGeohash.connect! is only necessary if you want to use LookupTables.

require "redis"
require "redis_geohash"

my_redis = Redis.new
RedisGeohash.connect!(my_redis)

location aware lists

Every RedisGeohash::LookupTable will create 8 redis-keys (hashes). Precision can be 0-8. Use :no_reverse_lookup => true to disable the second lookup pass (much faster, less acurate).

# create a namespace
geo_tbl = RedisGeohash::LookupTable.new('my_world')

# store the first items
geo_tbl.store!(:id => '23422342', :lat => ..., :lng => ...)
geo_tbl.store!(:id => '55552323', :lat => ..., :lng => ...)

# do a radius/grid search
geo_tbl.lookup(:lat => ..., :lng => ..., :precision => 4)
# => ['23422342', '55552323', ...]

# do a fast radius/grid search
geo_tbl.lookup(:lat => ..., :lng => ..., :precision => 4, :no_reverse_lookup => true)
# => ['23422342', '55552323', ...]

creating hashes manually

Hashes can be created without a redis connection

# create from lat/lng
geo_hash = RedisGeohash::GeoHash.new(:lat => ..., :lng => ...)

# create from geohash string
geo_hash = RedisGeohash::GeoHash.new("u33dc1f0j1nqg")

geo_hash.geohash
# => "u33dc1f0j1nqg"

geo_hash.coordinates
# => {:lat => ..., :lng => ...}

geo_hash.adjacents
# => [<GeoHash geohash="...">, <GeoHash geohash="...">, ...]

bonus: distance calculation

Pass in two lat/lng-hashes or two RedisGeohash::GeoHash objects.

RedisGeohash.distance({:lat => ..., :lng => ...}, {:lat => ..., :lng => ...})
#  => 34,654

RedisGeohash.distance(geo_hash_one, geo_hash_two)
#  => 34,654

Installation

gem install redis_geohash

or in your Gemfile:

gem 'redis_geohash', '~> 0.1'

Caveats

There is currently no (atomic) way to remove ids from a table

Todos

remove range monkeypatch

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to use, copy and modify copies of the Software, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

lauraschlimmer/redis_geohash