次のPiP検索は、ユーザーが住所またはlat / lng（http://staging.placeanddisplaced.org）でニューヨークの政府地区を検索できるようにするプロジェクト用に作成されました。動作しますが、特に複雑なポリゴンを持つ地区を検索する場合は、少し遅くなります。誰かが私にこのコードを最適化するためのいくつかの指針を与えることができますか？
私が持っていた1つの考えは、point_in_polygonを実行することでしたか？各ポリゴンの簡略化されたバージョン、つまりより少ない座標での方法。これは、処理時間が短くなるだけでなく、精度も低下することを意味します。
class DistrictPolygonsController < ApplicationController
def index
...
if coordinates?
@district_polygons = DistrictPolygon.
coordinates_within_bounding_box(params[:lat], params[:lng]).
find(:all, :include => :district, :select => select).
select { |dp| dp.contains_coordinates?(params[:lat], params[:lng]) }
else
@district_polygons = DistrictPolygon.find(:all, :include => :district, :select => select)
end
...
end
end
class DistrictPolygon < ActiveRecord::Base
named_scope :coordinates_within_bounding_box, lambda { |lat,lng| { :conditions => ['min_lat<? AND max_lat>? AND min_lng<? AND max_lng>?', lat.to_f, lat.to_f, lng.to_f, lng.to_f] } }
named_scope :with_district_type, lambda { |t| { :conditions => ['district_type=?', t] } }
before_save :get_bounding_box_from_geometry
def get_bounding_box_from_geometry
# return true unless self.new_record? || self.geometry_changed? || self.bounds_unknown?
self.min_lat = all_lats.min
self.max_lat = all_lats.max
self.min_lng = all_lngs.min
self.max_lng = all_lngs.max
true # object won't save without this return
end
def bounds_unknown?
%w(min_lat max_lat min_lng max_lng).any? {|b| self[b.to_sym].blank? }
end
def bounds_known?; !bounds_unknown?; end
# Returns an array of XML objects containing each polygons coordinates
def polygons
Nokogiri::XML(self.geometry).search("Polygon/outerBoundaryIs/LinearRing/coordinates")
end
def multi_geometric?
Nokogiri::XML(self.geometry).search("MultiGeometry").size > 0
end
# Returns an array of [lng,lat] arrays
def all_coordinates
pairs = []
polygons.map do |polygon|
polygon.content.split("\n").map do |coord|
# Get rid of third 'altitude' param from coordinate..
pair = coord.strip.split(",")[0..1].map(&:to_f)
# Don't let any nils, blanks, or zeros through..
pairs << pair unless pair.any? {|point| point.blank? || point.zero? }
end
end
pairs
end
# All latitudes, regardless of MultiPolygonal geometry
def all_lats
all_coordinates.map(&:last).reject{|lat| lat.blank? || lat.zero?}
end
# All longitudes, regardless of MultiPolygonal geometry
def all_lngs
all_coordinates.map(&:first).reject{|lng| lng.blank? || lng.zero?}
end
# Check to see if coordinates are in the rectangular bounds of this district
def contains_coordinates?(lat, lng)
return false unless coordinates_within_bounding_box?(lat.to_f, lng.to_f)
polygons.any? { |polygon| DistrictPolygon.point_in_polygon?(all_lats, all_lngs, lat.to_f, lng.to_f) }
end
def coordinates_within_bounding_box?(lat, lng)
return false if (max_lat > lat.to_f == min_lat > lat.to_f) # Not between lats
return false if (max_lng > lng.to_f == min_lng > lng.to_f) # Not between lngs
true
end
# This algorithm came from http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html
def self.point_in_polygon?(x_points, y_points, x_target, y_target)
num_points = x_points.size
j = num_points-1
c = false
for i in 0...num_points do
c = !c if ( ((y_points[i]>y_target) != (y_points[j]>y_target)) && (x_target < (x_points[j]-x_points[i]) * (y_target-y_points[i]) / (y_points[j]-y_points[i]) + x_points[i]) )
j = i
end
return c
end
end