VRFS-3316 : Reduce method to roll up reviews

* Creates review_summaries
* Calculate and store wilson score
* Unit tests

ruby/lib/jam_ruby/models/review.rb

@@ -10,11 +10,35 @@ module JamRuby
     validates :target, presence:true
     validates :user, presence:true
     validates :target_id, uniqueness: {scope: :user_id, message: "There is already a review for this User and Target."}
-    
-    # # @options - can contain values:
-    # # * target_id (optional)
-    # def reduce(options)
-    #   arel = Review.where("deleted_at=?", nil)
-    # end
+
+    class << self
+      # Create review_summary records by grouping reviews 
+      def reduce()
+        ReviewSummary.transaction do
+          ReviewSummary.destroy_all
+          Review.select("target_id, target_type AS target_type, AVG(rating) as avg_rating, count(*) as review_count, SUM(CASE WHEN rating>=3.0 THEN 1 ELSE 0 END) AS pos_count").group("target_type, target_id")
+                 .each do |r|
+            #puts "Reducing reviews: #{r.inspect} #{r.pos_count} / #{r.review_count}"
+            ReviewSummary.create!(
+              target_id:        r.target_id,
+              target_type:      r.target_type,
+              avg_rating:       r.avg_rating,
+              wilson_score:     ci_lower_bound(r.pos_count, r.review_count),
+              review_count:     r.review_count
+            )
+          end # each
+        end # transaction
+      end # reduce
+
+      def ci_lower_bound(pos, n, confidence=0.95)
+        pos=pos.to_f
+        n=n.to_f
+        return 0 if n == 0
+        z = 1.96 # Statistics2.pnormaldist(1-(1-confidence)/2)
+        phat = 1.0*pos/n
+        (phat + z*z/(2*n) - z * Math.sqrt((phat*(1-phat)+z*z/(4*n))/n))/(1+z*z/n)
+      end
+
+    end # self
   end
 end

ruby/lib/jam_ruby/models/review_summary.rb

@@ -1,12 +1,13 @@
 module JamRuby
   class ReviewSummary < ActiveRecord::Base
-    attr_accessible :target, :target_type, :avg_rating, :wilson_score, :review_count
+    attr_accessible :target, :target_id, :target_type, :avg_rating, :wilson_score, :review_count
     belongs_to :target, polymorphic: true
 
     validates :avg_rating, presence:true, numericality: true
     validates :review_count, presence:true, numericality: {only_integer: true}
     validates :wilson_score, presence:true, numericality: {greater_than:0, less_than:1}
-    validates :target, presence:true
-    validates :target_id, uniqueness:true
+    validates :target_id, presence:true, uniqueness:true
+
+
   end
 end

ruby/spec/factories.rb

@@ -139,6 +139,17 @@ FactoryGirl.define do
     end
   end
 
+  factory :review, :class => JamRuby::Review do
+    sequence(:name)  { |n| "Band" }
+    biography "My Biography"
+    city "Apex"
+    state "NC"
+    country "US"
+    before(:create) { |review|
+      review.genres << Genre.first
+    }
+  end
+
   factory :music_session, :class => JamRuby::MusicSession do
     sequence(:name) { |n| "Music Session #{n}" }
     sequence(:description) { |n| "Music Session Description #{n}" }

ruby/spec/jam_ruby/models/review_spec.rb

@@ -46,8 +46,33 @@ describe Review do
         review2 = Review.create(target:target, rating:3, user:@user)
         review2.valid?.should be_false
       end
-    end
 
+      it "reduces" do
+        review = Review.create(target:target, rating:3, user:@user)
+        review.valid?.should be_true
+
+        review2 = Review.create(target:target, rating:5, user:FactoryGirl.create(:user))
+        review2.valid?.should be_true
+        Review.count.should eq(2)
+        ReviewSummary.count.should eq(0)
+        Review.reduce()
+        ReviewSummary.count.should eq(1)
+        ReviewSummary.first.avg_rating.should eq(4.0)
+
+        puts "ORIG: #{ReviewSummary.all.inspect}"
+        ws_orig = ReviewSummary.first.wilson_score
+        avg_orig = ReviewSummary.first.avg_rating
+
+        5.times {Review.create(target:target, rating:5, user:FactoryGirl.create(:user))}
+        Review.reduce()
+
+        ReviewSummary.first.wilson_score.should > ws_orig
+        ReviewSummary.first.avg_rating.should > avg_orig
+
+        puts "ALL: #{ReviewSummary.all.inspect}"
+      end
+    end # context
+  
     context "validates review summary" do
       it "blank target" do
         review_summary = ReviewSummary.create()
@@ -99,4 +124,5 @@ describe Review do
     it_behaves_like :review, @jam_track, "jam_track"
   end
 
+
 end