outcomes speed improvements

refs CNVS-12716

test plan:
  - make course with many assessed outcomes
  - load the mastery gradebook
  - it should load relatively fast

Change-Id: I81a91d58d37e5ae3d5399d59f6e3626af53496ea
Reviewed-on: https://gerrit.instructure.com/53493
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Deepeeca Soundarrajan <dsoundarrajan@instructure.com>
Tested-by: Jenkins
Product-Review: Hilary Scharton <hilary@instructure.com>

Author: Michael Nomitch

app/models/learning_outcome.rb

@@ -295,7 +295,11 @@ def destroy
   end
 
   def assessed?
-    learning_outcome_results.exists?
+    if learning_outcome_results.loaded?
+      learning_outcome_results.any?
+    else
+      learning_outcome_results.exists?
+    end
   end
 
   def tie_to(context)

db/migrate/20150505173732_add_learning_outcome_index_to_outcome_results.rb

@@ -0,0 +1,12 @@
+class AddLearningOutcomeIndexToOutcomeResults < ActiveRecord::Migration
+  tag :postdeploy
+  disable_ddl_transaction!
+
+  def up
+    add_index :learning_outcome_results, :learning_outcome_id, algorithm: :concurrently, where: "learning_outcome_id IS NOT NULL"
+  end
+
+  def down
+    remove_index :learning_outcome_results, :learning_outcome_id
+  end
+end

lib/api/v1/outcome_results.rb

@@ -60,8 +60,12 @@ def outcome_results_rollups_json(rollups)
   #
   # Returns a Hash containing serialized outcomes.
   def outcome_results_include_outcomes_json(outcomes)
+    ActiveRecord::Associations::Preloader.new(outcomes, [:context, :alignments]).run
+    assessed_outcomes = LearningOutcomeResult.uniq
+      .where(learning_outcome_id: outcomes.map(&:id))
+      .pluck(:learning_outcome_id)
     outcomes.map do |o|
-      hash = outcome_json(o, @current_user, session)
+      hash = outcome_json(o, @current_user, session, assessed_outcomes: assessed_outcomes)
       hash.merge!(alignments: o.alignments.map(&:content_asset_string))
       Api.recursively_stringify_json_ids(hash)
     end

lib/outcomes/result_analytics.rb

@@ -62,6 +62,7 @@ def order_results_for_rollup(relation)
     #
     # Returns an Array of Rollup objects.
     def outcome_results_rollups(results, users=[])
+      ActiveRecord::Associations::Preloader.new(results, :learning_outcome).run
       rollups = results.chunk(&:user_id).map do |_, user_results|
         Rollup.new(user_results.first.user, rollup_user_results(user_results))
       end
@@ -82,7 +83,9 @@ def aggregate_outcome_results_rollup(results, context)
       aggregate_results = outcome_results.map do |scores|
         scores.map{|score| Result.new(score.outcome, score.score, score.count)}
       end
-      aggregate_rollups = aggregate_results.map{|result| RollupScore.new(result,{aggregate_score: true})}
+      aggregate_rollups = aggregate_results.map do |result|
+        RollupScore.new(result,{aggregate_score: true})
+      end
       Rollup.new(context, aggregate_rollups)
     end
 

spec/lib/outcomes/result_analytics_spec.rb

@@ -167,6 +167,9 @@ def user_id
   end
 
   describe '#outcome_results_rollups' do
+    before do
+      ActiveRecord::Associations::Preloader.any_instance.stubs(:run)
+    end
     it 'returns a rollup for each distinct user_id' do
       results = [
         MockOutcomeResult[MockUser[10, 'a'], MockOutcome[80], 4.0],
@@ -183,6 +186,9 @@ def user_id
   end
 
   describe '#aggregate_outcome_results_rollup' do
+    before do
+      ActiveRecord::Associations::Preloader.any_instance.stubs(:run)
+    end
     it 'returns one rollup with the rollup averages' do
       fake_context = MockUser.new(42, 'fake')
       results = [