Adds get all medians to Cycle Analytics model

3 files changed, 74 insertions, 5 deletions

diff --git a/lib/gitlab/cycle_analytics/base_query.rb b/lib/gitlab/cycle_analytics/base_query.rb
index 8b3bc3e440d..fee46fc0dda 100644
--- a/lib/gitlab/cycle_analytics/base_query.rb
+++ b/lib/gitlab/cycle_analytics/base_query.rb
@@ -14,7 +14,7 @@ module Gitlab
       def stage_query
         query = mr_closing_issues_table.join(issue_table).on(issue_table[:id].eq(mr_closing_issues_table[:issue_id]))
           .join(issue_metrics_table).on(issue_table[:id].eq(issue_metrics_table[:issue_id]))
-          .where(issue_table[:project_id].eq(@project.id)) # rubocop:disable Gitlab/ModuleWithInstanceVariables
+          .where(issue_table[:project_id].in(project_ids)) # rubocop:disable Gitlab/ModuleWithInstanceVariables
           .where(issue_table[:created_at].gteq(@options[:from])) # rubocop:disable Gitlab/ModuleWithInstanceVariables
 
         # Load merge_requests
@@ -22,9 +22,14 @@ module Gitlab
           .on(mr_table[:id].eq(mr_closing_issues_table[:merge_request_id]))
           .join(mr_metrics_table)
           .on(mr_table[:id].eq(mr_metrics_table[:merge_request_id]))
+          .project(issue_table[:project_id].as("project_id"))
 
         query
       end
+
+      def project_ids
+        @projects.map(&:id)
+      end
     end
   end
 end
diff --git a/lib/gitlab/cycle_analytics/base_stage.rb b/lib/gitlab/cycle_analytics/base_stage.rb
index cac31ea8cff..c9de27ec481 100644
--- a/lib/gitlab/cycle_analytics/base_stage.rb
+++ b/lib/gitlab/cycle_analytics/base_stage.rb
@@ -3,8 +3,8 @@ module Gitlab
     class BaseStage
       include BaseQuery
 
-      def initialize(project:, options:)
-        @project = project
+      def initialize(projects:, options:)
+        @projects = projects
         @options = options
       end
 
@@ -20,7 +20,7 @@ module Gitlab
         raise NotImplementedError.new("Expected #{self.name} to implement title")
       end
 
-      def median
+      def medians
         cte_table = Arel::Table.new("cte_table_for_#{name}")
 
         # Build a `SELECT` query. We find the first of the `end_time_attrs` that isn't `NULL` (call this end_time).
@@ -31,7 +31,7 @@ module Gitlab
           cte_table,
           subtract_datetimes(base_query.dup, start_time_attrs, end_time_attrs, name.to_s))
 
-        median_datetime(cte_table, interval_query, name)
+        median_datetimes(cte_table, interval_query, name)
       end
 
       def name
diff --git a/lib/gitlab/cycle_analytics/usage_data.rb b/lib/gitlab/cycle_analytics/usage_data.rb
new file mode 100644
index 00000000000..43ec9f9c493
--- /dev/null
+++ b/lib/gitlab/cycle_analytics/usage_data.rb
@@ -0,0 +1,64 @@
+module Gitlab
+  module CycleAnalytics
+    class UsageData
+      PROJECTS_LIMIT = 10
+
+      attr_reader :projects, :options
+
+      def initialize(projects, options)
+        @projects = projects
+        @options = options
+      end
+
+      def to_json
+        total = 0
+        values = {}
+
+        medians_per_stage.each do |stage_name, medians|
+          medians = medians.compact
+
+          stage_values = {
+            average: calc_average(medians),
+            sd: standard_deviation(medians),
+            missing: projects.length - medians.length
+          }
+
+          total += stage_values.values.compact.sum
+          values[stage_name] = stage_values
+        end
+
+        values[:total] = total
+
+        { avg_cycle_analytics: values }
+      end
+
+      private
+
+      def medians_per_stage
+        @medians_per_stage ||= ::CycleAnalytics.all_medians_per_stage(projects, options)
+      end
+
+      def calc_average(values)
+        return if values.empty?
+
+        (values.sum / values.length).to_i
+      end
+
+      def sample_variance(values)
+        return 0 if values.length <= 1
+
+        avg = calc_average(values)
+        sum = values.inject(0) do |acc, val|
+          acc + (val - avg)**2
+        end
+
+        sum / (values.length - 1)
+      end
+
+      def standard_deviation(values)
+        Math.sqrt(sample_variance(values)).to_i
+      end
+    end
+  end
+end
+