Optimize places memory usage by paginating, plucking fields, and limiting nearest_to (#4792)

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: Brenda Wallace <brenda@wallace.net.nz>

app/controllers/places_controller.rb

@@ -4,14 +4,17 @@ class PlacesController < ApplicationController
   skip_authorize_resource
   respond_to :html, :json
 
+  MEMBER_FIELDS = %i[id login_name slug location latitude longitude].freeze
+
   def index
     respond_to do |format|
       format.html
       # json response is whatever we want to map here
       format.json do
-        render json: Member.located.to_json(only: %i(
-                                              id login_name slug location latitude longitude
-                                            ))
+        members = Member.located.paginate(page: params[:page]).pluck(*MEMBER_FIELDS).map do |row|
+          MEMBER_FIELDS.zip(row).to_h
+        end
+        render json: members
       end
     end
   end
@@ -24,9 +27,7 @@ class PlacesController < ApplicationController
     respond_to do |format|
       format.html # show.html.haml
       format.json do
-        render json: @nearby_members.to_json(only: %i(
-                                               id login_name slug location latitude longitude
-                                             ))
+        render json: @nearby_members.as_json(only: MEMBER_FIELDS)
       end
     end
   end

app/models/member.rb

@@ -173,13 +173,14 @@ class Member < ApplicationRecord
     where(["lower(login_name) = :value", { value: login.downcase }])
   end
 
-  def self.nearest_to(place)
-    return [] if place.blank?
+  def self.nearest_to(place, limit = 50)
+    return Member.none if place.blank?
 
     latitude, longitude = Geocoder.coordinates(place, params: { limit: 1 })
-    return [] unless latitude && longitude
+    return Member.none unless latitude && longitude
 
-    Member.located.near([latitude, longitude], 1000)
+    relation = Member.located.near([latitude, longitude], 1000)
+    limit ? relation.limit(limit) : relation
   end
 
   def already_following?(member)

spec/controllers/places_controller_spec.rb

@@ -7,6 +7,26 @@ describe PlacesController do
     controller.stub(:current_member) { nil }
   end
 
+  describe "GET index" do
+    before do
+      @london_member = create(:london_member)
+    end
+
+    it "renders the index template for HTML request" do
+      get :index
+      response.should render_template(:index)
+    end
+
+    it "returns JSON with paginated located members" do
+      get :index, format: :json
+      response.should be_successful
+      json = JSON.parse(response.body)
+      expect(json).to be_an(Array)
+      expect(json.first["login_name"]).to eq(@london_member.login_name)
+      expect(json.first.keys).to match_array(%w(id login_name slug location latitude longitude))
+    end
+  end
+
   describe "GET show" do
     before do
       @london_member = create(:london_member)
@@ -22,6 +42,15 @@ describe PlacesController do
       get :show, params: { place: @london_member.location }
       assigns(:nearby_members).should eq [@london_member, @edinburgh_member]
     end
+
+    it "returns JSON with nearby members" do
+      get :show, params: { place: @london_member.location }, format: :json
+      response.should be_successful
+      json = JSON.parse(response.body)
+      expect(json).to be_an(Array)
+      expect(json.map { |m| m["login_name"] }).to eq([@london_member.login_name, @edinburgh_member.login_name])
+      expect(json.first.keys).to match_array(%w(id login_name slug location latitude longitude))
+    end
   end
 
   describe "GET search" do

spec/models/member_spec.rb

@@ -250,6 +250,17 @@ describe Member do
       london_member = create(:london_member)
       Member.nearest_to('Greenwich, UK').should eq [london_member, edinburgh_member]
     end
+
+    it 'returns Member.none when place is blank or un-geocoded' do
+      expect(Member.nearest_to('')).to eq Member.none
+      expect(Member.nearest_to(nil)).to eq Member.none
+    end
+
+    it 'respects the limit parameter' do
+      create(:edinburgh_member)
+      create(:london_member)
+      expect(Member.nearest_to('Greenwich, UK', 1).to_a.size).to eq 1
+    end
   end
 
   describe 'interesting scope' do