Merge pull request #321 from mlandauer/bounding_box_2

Add bounding box optimisation

README.md

@@ -527,6 +527,15 @@ Calling `obj.coordinates` directly returns the internal representation of the co
 
 For consistency with the rest of Geocoder, always use the `to_coordinates` method instead.
 
+Optimisation of Distance Queries
+--------------------------------
+
+In MySQL and Postgres the finding of objects near a given point is speeded up by using a bounding box to limit the number of points over which a full distance calculation needs to be done.
+
+To take advantage of this optimisation you need to add a composite index on latitude and longitude. In your Rails migration:
+
+    add_index :table, [:latitude, :longitude]
+
 
 Distance Queries in SQLite
 --------------------------

lib/geocoder/stores/active_record.rb

@@ -102,15 +102,18 @@ module Geocoder::Store
         options[:units] ||= (geocoder_options[:units] || Geocoder::Configuration.units)
         bearing = bearing_sql(latitude, longitude, options)
         distance = distance_sql(latitude, longitude, options)
+
+        b = Geocoder::Calculations.bounding_box([latitude, longitude], radius, options)
+        args = b + [
+          full_column_name(geocoder_options[:latitude]),
+          full_column_name(geocoder_options[:longitude])
+        ]
+        bounding_box_conditions = Geocoder::Sql.within_bounding_box(*args)
+
         if using_sqlite?
-          b = Geocoder::Calculations.bounding_box([latitude, longitude], radius, options)
-          args = b + [
-            full_column_name(geocoder_options[:latitude]),
-            full_column_name(geocoder_options[:longitude])
-          ]
-          conditions = Geocoder::Sql.within_bounding_box(*args)
+          conditions = bounding_box_conditions
         else
-          conditions = ["#{distance} <= ?", radius]
+          conditions = [bounding_box_conditions + " AND #{distance} <= ?", radius]
         end
         {
           :select => select_clause(options[:select], distance, bearing),

test/near_test.rb

+require 'test_helper'
+
+class NearTest < Test::Unit::TestCase
+
+  def test_near_scope_options_without_sqlite_includes_bounding_box_condition
+    result = Event.send(:near_scope_options, 1.0, 2.0, 5)
+
+    assert_match /test_table_name.latitude BETWEEN 0.9276\d* AND 1.0723\d* AND test_table_name.longitude BETWEEN 1.9276\d* AND 2.0723\d* AND /,
+      result[:conditions][0]
+  end
+end

test/test_helper.rb

@@ -4,6 +4,12 @@ require 'test/unit'
 $LOAD_PATH.unshift(File.dirname(__FILE__))
 $LOAD_PATH.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))
 
+class MysqlConnection
+  def adapter_name
+    "mysql"
+  end
+end
+
 ##
 # Simulate enough of ActiveRecord::Base that objects can be used for testing.
 #
@@ -28,6 +34,10 @@ module ActiveRecord
 
     def self.scope(*args); end
 
+    def self.connection
+      MysqlConnection.new
+    end
+
     def method_missing(name, *args, &block)
       if name.to_s[-1..-1] == "="
         write_attribute name.to_s[0...-1], *args