Moved popular plant plarts calculation into sql

app/models/crop.rb

@@ -163,11 +163,11 @@ class Crop < ActiveRecord::Base
   # key: plant part (eg. 'fruit')
   # value: count of how many times it's been used by harvests
   def popular_plant_parts
-    popular_plant_parts = Hash.new(0)
-    harvests.each do |h|
-      popular_plant_parts[h.plant_part] += 1 if h.plant_part
-    end
-    popular_plant_parts.sort_by { |_s, freq| freq }.reverse
+    PlantPart.joins(:harvests)
+      .where("crop_id = ?", id)
+      .order("count_harvests_id DESC")
+      .group("plant_parts.id", "plant_parts.name")
+      .count("harvests.id")
   end
 
   def interesting?

app/views/crops/_grown_for.html.haml

@@ -3,6 +3,7 @@
   - if crop.harvests.empty?
     not known.
   - else
-    - crop.popular_plant_parts.map do |plant_part, frequency|
-      = link_to plant_part.name, plant_part_path(plant_part)
+    - crop.popular_plant_parts.each do |plant_part, frequency|
+    - id, name = plant_part
+      = link_to name, plant_part_path(id: id)
       (#{frequency})

spec/models/crop_spec.rb

@@ -248,9 +248,9 @@ describe Crop do
 
     it 'counts each plant_part value' do
       @fruit = FactoryGirl.create(:plant_part)
-      @seed = FactoryGirl.create(:plant_part)
-      @root = FactoryGirl.create(:plant_part)
-      @bulb = FactoryGirl.create(:plant_part)
+      @seed = FactoryGirl.create(:plant_part, name: 'seed')
+      @root = FactoryGirl.create(:plant_part, name: 'root')
+      @bulb = FactoryGirl.create(:plant_part, name: 'bulb')
       @harvest1 = FactoryGirl.create(:harvest,
         crop: crop,
         plant_part: @fruit
@@ -267,7 +267,9 @@ describe Crop do
         crop: crop,
         plant_part: @root
       )
-      crop.popular_plant_parts.should == { @fruit => 2, @seed => 1, @root => 1 }
+      crop.popular_plant_parts.should == { [@fruit.id, @fruit.name] => 2,
+                                           [@seed.id, @seed.name] => 1,
+                                           [@root.id, @root.name] => 1 }
     end
   end