Add the "Code" Cycle Analytics section.

1. Record the `wip_flag_first_removed_at` and
   `first_assigned_to_user_other_than_author` metrics for a merge
   request. Use a `merge_request_metrics` table, similar to the one for
   `issues`. Metrics are recorded `after_save`.

2. Move larger queries to a `CycleAnalytics::Queries` module.

app/models/cycle_analytics.rb

@@ -2,20 +2,22 @@ class CycleAnalytics
   def issue
     issues = Issue.includes(:metrics).where("issue_metrics.id IS NOT NULL").references(:issue_metrics).to_a
     start_time_fn = -> (issue) { issue.created_at  }
-    end_time_fn = -> (issue) { issue.metrics.first_associated_with_milestone_at.presence || issue.metrics.first_added_to_board_at.presence }
-
-    calculate_metric(issues, start_time_fn, end_time_fn)
+    calculate_metric(issues, start_time_fn, Queries::issue_first_associated_with_milestone_or_first_added_to_list_label_time)
   end
 
   def plan
     issues = Issue.includes(:metrics).where("issue_metrics.id IS NOT NULL").references(:issue_metrics).to_a
-    start_time_fn = -> (issue) { issue.metrics.first_associated_with_milestone_at.presence || issue.metrics.first_added_to_board_at.presence }
-    end_time_fn = lambda do |issue|
-      merge_requests = issue.closed_by_merge_requests
-      merge_requests.map(&:created_at).min if merge_requests.present?
+    calculate_metric(issues,
+                     Queries::issue_first_associated_with_milestone_or_first_added_to_list_label_time,
+                     Queries::issue_closing_merge_request_opened_time)
   end
 
-    calculate_metric(issues, start_time_fn, end_time_fn)
+  def code
+    issues = Issue.all.to_a
+    start_time_fn = -> (merge_request) { merge_request.created_at }
+    calculate_metric(issues.map(&:closed_by_merge_requests).flatten,
+                     start_time_fn,
+                     Queries::mr_wip_flag_removed_or_assigned_to_user_other_than_author_time)
   end
 
   private
@@ -34,6 +36,7 @@ class CycleAnalytics
   end
 
   def median(coll)
+    return if coll.empty?
     size = coll.length
     (coll[size / 2] + coll[(size - 1) / 2]) / 2.0
   end

app/models/cycle_analytics/queries.rb

+class CycleAnalytics
+  module Queries
+    class << self
+      def issue_first_associated_with_milestone_or_first_added_to_list_label_time
+        lambda do |issue|
+          issue.metrics.first_associated_with_milestone_at.presence || issue.metrics.first_added_to_board_at.presence
+        end
+      end
+
+      def issue_closing_merge_request_opened_time
+        lambda do |issue|
+          merge_requests = issue.closed_by_merge_requests
+          merge_requests.map(&:created_at).min if merge_requests.present?
+        end
+      end
+
+      def mr_wip_flag_removed_or_assigned_to_user_other_than_author_time
+        lambda do |merge_request|
+          if merge_request.metrics.present?
+            merge_request.metrics.wip_flag_first_removed_at || merge_request.metrics.first_assigned_to_user_other_than_author
+          end
+        end
+      end
+    end
+  end
+end

app/models/merge_request.rb

@@ -13,6 +13,7 @@ class MergeRequest < ActiveRecord::Base
   has_many :merge_request_diffs, dependent: :destroy
   has_one :merge_request_diff,
     -> { order('merge_request_diffs.id DESC') }
+  has_one :metrics, dependent: :destroy
 
   has_many :events, as: :target, dependent: :destroy
 
@@ -31,6 +32,8 @@ class MergeRequest < ActiveRecord::Base
   # when creating new merge request
   attr_accessor :can_be_created, :compare_commits, :compare
 
+  after_save :record_metrics
+
   state_machine :state, initial: :opened do
     event :close do
       transition [:reopened, :opened] => :closed
@@ -807,4 +810,9 @@ class MergeRequest < ActiveRecord::Base
       @conflicts_can_be_resolved_in_ui = false
     end
   end
+
+  def record_metrics
+    metrics = Metrics.find_or_create_by(merge_request_id: self.id)
+    metrics.record!
+  end
 end

app/models/merge_request/metrics.rb

+class MergeRequest::Metrics < ActiveRecord::Base
+  belongs_to :merge_request
+
+  def record!
+    if !merge_request.work_in_progress? && self.wip_flag_first_removed_at.blank?
+      self.wip_flag_first_removed_at = Time.now
+    end
+
+    if merge_request.author_id != merge_request.assignee_id && self.first_assigned_to_user_other_than_author.blank?
+      self.first_assigned_to_user_other_than_author = Time.now
+    end
+
+    self.save if self.changed?
+  end
+end

app/views/projects/cycle_analytics/show.html.haml

 %ul.list-group
   %li.list-group-item
     Issue:
-    = distance_of_time_in_words @cycle_analytics.issue
+    - if issue = @cycle_analytics.issue
+      = distance_of_time_in_words issue
+    - else
+      <Not enough data>
 
   %li.list-group-item
     Plan:
-    = distance_of_time_in_words @cycle_analytics.plan
+    - if plan = @cycle_analytics.plan
+      = distance_of_time_in_words plan
+    - else
+      <Not enough data>
+
+  %li.list-group-item
+    Code:
+    - if code = @cycle_analytics.code.presence
+      = distance_of_time_in_words code
+    - else
+      = "<Not enough data>"

db/migrate/20160825052008_add_table_merge_request_metrics.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddTableMergeRequestMetrics < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  # When a migration requires downtime you **must** uncomment the following
+  # constant and define a short and easy to understand explanation as to why the
+  # migration requires downtime.
+  # DOWNTIME_REASON = ''
+
+  # When using the methods "add_concurrent_index" or "add_column_with_default"
+  # you must disable the use of transactions as these methods can not run in an
+  # existing transaction. When using "add_concurrent_index" make sure that this
+  # method is the _only_ method called in the migration, any other changes
+  # should go in a separate migration. This ensures that upon failure _only_ the
+  # index creation fails and can be retried or reverted easily.
+  #
+  # To disable transactions uncomment the following line and remove these
+  # comments:
+  # disable_ddl_transaction!
+
+  def change
+    create_table :merge_request_metrics do |t|
+      t.references :merge_request, index: { name: "index_merge_request_metrics" }, foreign_key: true, null: false
+
+      t.datetime 'wip_flag_first_removed_at'
+      t.datetime 'first_assigned_to_user_other_than_author'
+
+      t.timestamps null: false
+    end
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160824124900) do
+ActiveRecord::Schema.define(version: 20160825052008) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -605,6 +605,16 @@ ActiveRecord::Schema.define(version: 20160824124900) do
 
   add_index "merge_request_diffs", ["merge_request_id"], name: "index_merge_request_diffs_on_merge_request_id", using: :btree
 
+  create_table "merge_request_metrics", force: :cascade do |t|
+    t.integer  "merge_request_id",                         null: false
+    t.datetime "wip_flag_first_removed_at"
+    t.datetime "first_assigned_to_user_other_than_author"
+    t.datetime "created_at",                               null: false
+    t.datetime "updated_at",                               null: false
+  end
+
+  add_index "merge_request_metrics", ["merge_request_id"], name: "index_merge_request_metrics", using: :btree
+
   create_table "merge_requests", force: :cascade do |t|
     t.string   "target_branch",                                null: false
     t.string   "source_branch",                                null: false
@@ -1163,6 +1173,7 @@ ActiveRecord::Schema.define(version: 20160824124900) do
   add_foreign_key "issue_metrics", "issues"
   add_foreign_key "lists", "boards"
   add_foreign_key "lists", "labels"
+  add_foreign_key "merge_request_metrics", "merge_requests"
   add_foreign_key "personal_access_tokens", "users"
   add_foreign_key "protected_branch_merge_access_levels", "protected_branches"
   add_foreign_key "protected_branch_push_access_levels", "protected_branches"