Use the aggregated tables for duration chart

ee/lib/ee/gitlab/analytics/cycle_analytics/aggregated/data_collector.rb

+# frozen_string_literal: true
+
+module EE
+  module Gitlab
+    module Analytics
+      module CycleAnalytics
+        module Aggregated
+          module DataCollector
+            def duration_chart_average_data
+              ::Gitlab::Analytics::CycleAnalytics::Aggregated::DataForDurationChart
+                .new(stage: stage, params: params, query: query)
+                .average_by_day
+            end
+          end
+        end
+      end
+    end
+  end
+end

ee/lib/ee/gitlab/analytics/cycle_analytics/data_collector.rb

@@ -6,8 +6,12 @@ module EE
       module CycleAnalytics
         module DataCollector
           def duration_chart_average_data
-            strong_memoize(:duration_chart_average_data) do
-              duration_chart.average_by_day
+            strong_memoize(:records_fetcher) do
+              if use_aggregated_data_collector?
+                aggregated_data_collector.duration_chart_average_data
+              else
+                duration_chart.average_by_day
+              end
             end
           end
 

ee/lib/gitlab/analytics/cycle_analytics/aggregated/data_for_duration_chart.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    module CycleAnalytics
+      module Aggregated
+        class DataForDurationChart
+          include StageQueryHelpers
+
+          def initialize(stage:, params:, query:)
+            @stage = stage
+            @params = params
+            @query = query
+          end
+
+          # rubocop: disable CodeReuse/ActiveRecord
+          def average_by_day
+            @query
+              .group(date_expression)
+              .select(date_expression.as('date'), duration.average.as('average_duration_in_seconds'))
+          end
+          # rubocop: enable CodeReuse/ActiveRecord
+
+          private
+
+          attr_reader :stage, :query, :params
+
+          def date_expression
+            Arel::Nodes::NamedFunction.new('DATE', [query.model.arel_table[:end_event_timestamp]])
+          end
+        end
+      end
+    end
+  end
+end

ee/spec/lib/gitlab/analytics/cycle_analytics/aggregated/data_for_duration_chart_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Analytics::CycleAnalytics::Aggregated::DataForDurationChart do
+  let_it_be(:stage) { create(:cycle_analytics_group_stage, start_event_identifier: :issue_created, end_event_identifier: :issue_closed) }
+  let_it_be(:project) { create(:project, group: stage.group) }
+  let_it_be(:issue_1) { create(:issue, project: project) }
+  let_it_be(:issue_2) { create(:issue, project: project) }
+  let_it_be(:issue_3) { create(:issue, project: project) }
+
+  subject(:result) do
+    described_class
+      .new(stage: stage, params: {}, query: Analytics::CycleAnalytics::IssueStageEvent.all)
+      .average_by_day
+  end
+
+  it 'calculates the daily average stage duration' do
+    end_timestamp_1 = Time.zone.local(2020, 5, 6, 12, 0)
+    end_timestamp_2 = Time.zone.local(2020, 5, 15, 10, 0)
+
+    create(:cycle_analytics_issue_stage_event, issue_id: issue_1.id, start_event_timestamp: end_timestamp_1 - 3.days, end_event_timestamp: end_timestamp_1) # 3 days
+    create(:cycle_analytics_issue_stage_event, issue_id: issue_2.id, start_event_timestamp: end_timestamp_2 - 3.days, end_event_timestamp: end_timestamp_2) # 3 days
+    create(:cycle_analytics_issue_stage_event, issue_id: issue_3.id, start_event_timestamp: end_timestamp_2 - 1.day, end_event_timestamp: end_timestamp_2) # 1 day
+
+    average_two_days_ago = result[0]
+    average_today = result[1]
+
+    expect(average_two_days_ago).to have_attributes(date: end_timestamp_1.to_date, average_duration_in_seconds: 3.days)
+    expect(average_today).to have_attributes(date: end_timestamp_2.to_date, average_duration_in_seconds: 2.days)
+  end
+end

ee/spec/lib/gitlab/analytics/cycle_analytics/data_collector_spec.rb

@@ -138,6 +138,15 @@ RSpec.describe Gitlab::Analytics::CycleAnalytics::DataCollector do
           resource_2_end_time.utc.to_date => 5,
           resource_3_end_time.utc.to_date => 15
         })
+
+        if aggregated_data_collector_enabled
+          data = aggregated_data_collector.duration_chart_average_data.map { |item| [item.date, round_to_days(item.average_duration_in_seconds)] }
+          expect(Hash[data]).to eq({
+            resource_1_end_time.utc.to_date => 10,
+            resource_2_end_time.utc.to_date => 5,
+            resource_3_end_time.utc.to_date => 15
+          })
+        end
       end
     end
 

ee/spec/support/shared_examples/controllers/analytics/cycle_analytics/shared_stage_shared_examples.rb

@@ -280,7 +280,12 @@ RSpec.shared_examples 'Value Stream Analytics Stages controller' do
 
       it 'matches the response schema' do
         fake_result = [double(MergeRequest, average_duration_in_seconds: 10, date: Time.current.to_date)]
-        expect_any_instance_of(Gitlab::Analytics::CycleAnalytics::DataForDurationChart).to receive(:average_by_day).and_return(fake_result)
+
+        if Feature.enabled?(:use_vsa_aggregated_tables)
+          expect_any_instance_of(Gitlab::Analytics::CycleAnalytics::Aggregated::DataForDurationChart).to receive(:average_by_day).and_return(fake_result)
+        else
+          expect_any_instance_of(Gitlab::Analytics::CycleAnalytics::DataForDurationChart).to receive(:average_by_day).and_return(fake_result)
+        end
 
         subject
 

lib/gitlab/analytics/cycle_analytics/aggregated/data_collector.rb

@@ -52,3 +52,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::Analytics::CycleAnalytics::Aggregated::DataCollector.prepend_mod_with('Gitlab::Analytics::CycleAnalytics::Aggregated::DataCollector')