Use DateSourcingMilestonesFinder in migration

ee/db/post_migrate/20180713171825_update_epic_dates_from_milestones.rb

@@ -14,7 +14,7 @@ class UpdateEpicDatesFromMilestones < ActiveRecord::Migration
     has_many :epic_issues
     has_many :issues, through: :epic_issues
 
-    def self.update_dates(epics)
+    def self.update_start_and_due_dates(epics)
       groups = epics.includes(:issues).group_by do |epic|
         milestone_ids = epic.issues.map(&:milestone_id)
         milestone_ids.compact!
@@ -25,62 +25,29 @@ class UpdateEpicDatesFromMilestones < ActiveRecord::Migration
       groups.each do |milestone_ids, epics|
         next if milestone_ids.empty?
 
-        data = epics.first.fetch_milestone_date_data
+        data = ::Epics::DateSourcingMilestonesFinder.execute(epics.first.id)
 
         self.where(id: epics.map(&:id)).update_all(
           [
             %{
-                start_date = CASE WHEN start_date_is_fixed = true THEN start_date ELSE ? END,
-                start_date_sourcing_milestone_id = ?,
-                end_date = CASE WHEN due_date_is_fixed = true THEN end_date ELSE ? END,
-                due_date_sourcing_milestone_id = ?
-              },
-            data[:start_date],
-            data[:start_date_sourcing_milestone_id],
-            data[:due_date],
-            data[:due_date_sourcing_milestone_id]
+              start_date = CASE WHEN start_date_is_fixed = true THEN start_date ELSE ? END,
+              start_date_sourcing_milestone_id = ?,
+              end_date = CASE WHEN due_date_is_fixed = true THEN end_date ELSE ? END,
+              due_date_sourcing_milestone_id = ?
+            },
+            data.start_date,
+            data.start_date_sourcing_milestone_id,
+            data.due_date,
+            data.due_date_sourcing_milestone_id
           ]
         )
       end
     end
-
-    def fetch_milestone_date_data
-      sql = <<~SQL
-        SELECT milestones.id, milestones.start_date, milestones.due_date FROM milestones
-        INNER JOIN issues ON issues.milestone_id = milestones.id
-        INNER JOIN epic_issues ON epic_issues.issue_id = issues.id
-        INNER JOIN (
-          SELECT MIN(milestones.start_date) AS start_date, MAX(milestones.due_date) AS due_date
-          FROM milestones
-          INNER JOIN issues ON issues.milestone_id = milestones.id
-          INNER JOIN epic_issues ON epic_issues.issue_id = issues.id
-          WHERE epic_issues.epic_id = #{id}
-        ) inner_results ON (inner_results.start_date = milestones.start_date OR inner_results.due_date = milestones.due_date)
-        WHERE epic_issues.epic_id = #{id}
-      SQL
-
-      db_results = ActiveRecord::Base.connection.select_all(sql).to_a
-
-      results = {}
-      db_results
-        .reject { |row| row['start_date'].nil? }
-        .min_by { |row| row['start_date'] }&.tap do |row|
-        results[:start_date] = row['start_date']
-        results[:start_date_sourcing_milestone_id] = row['id']
-      end
-      db_results
-        .reject { |row| row['due_date'].nil? }
-        .max_by { |row| row['due_date'] }&.tap do |row|
-        results[:due_date] = row['due_date']
-        results[:due_date_sourcing_milestone_id] = row['id']
-      end
-      results
-    end
   end
 
   def up
     Epic.joins(:issues).where('issues.milestone_id IS NOT NULL').each_batch do |epics|
-      Epic.update_dates(epics)
+      Epic.update_start_and_due_dates(epics)
     end
   end
 

ee/spec/migrations/update_epic_dates_from_milestones_spec.rb

+require 'spec_helper'
+require Rails.root.join('ee', 'db', 'post_migrate', '20180713171825_update_epic_dates_from_milestones.rb')
+
+describe UpdateEpicDatesFromMilestones, :migration do
+  let(:migration) { described_class.new }
+  let(:users) { table(:users) }
+  let(:namespaces) { table(:namespaces) }
+  let(:epics) { table(:epics) }
+  let(:projects) { table(:projects) }
+  let(:issues) { table(:issues) }
+  let(:epic_issues) { table(:epic_issues) }
+  let(:milestones) { table(:milestones) }
+
+  describe '#up' do
+    before do
+      user = users.create!(email: 'test@example.com', projects_limit: 100, username: 'test')
+      namespaces.create(id: 1, name: 'gitlab-org', path: 'gitlab-org')
+      projects.create!(id: 1, namespace_id: 1, name: 'gitlab1', path: 'gitlab1')
+
+      epics.create!(id: 1, iid: 1, group_id: 1, title: 'epic with start and due dates', title_html: '', author_id: user.id)
+      epics.create!(id: 2, iid: 2, group_id: 1, title: 'epic with only due date', title_html: '', author_id: user.id)
+      epics.create!(id: 3, iid: 3, group_id: 1, title: 'epic without milestone', title_html: '', author_id: user.id)
+
+      milestones.create!(
+        id: 1,
+        iid: 1,
+        project_id: 1,
+        title: 'milestone-1',
+        start_date: Date.new(2000, 1, 1),
+        due_date: Date.new(2000, 1, 10)
+      )
+      milestones.create!(
+        id: 2,
+        iid: 2,
+        project_id: 1,
+        title: 'milestone-2',
+        due_date: Date.new(2000, 1, 30)
+      )
+
+      issues.create!(id: 1, iid: 1, project_id: 1, milestone_id: 1, title: 'issue-1')
+      issues.create!(id: 2, iid: 2, project_id: 1, milestone_id: 2, title: 'issue-2')
+      issues.create!(id: 3, iid: 3, project_id: 1, milestone_id: 2, title: 'issue-2')
+
+      epic_issues.create!(epic_id: 1, issue_id: 1)
+      epic_issues.create!(epic_id: 1, issue_id: 2)
+      epic_issues.create!(epic_id: 2, issue_id: 3)
+    end
+
+    it 'updates dates milestone ids' do
+      migration.up
+
+      expect(Epic.find(1)).to have_attributes(
+        start_date: Date.new(2000, 1, 1),
+        start_date_sourcing_milestone_id: 1,
+        due_date: Date.new(2000, 1, 30),
+        due_date_sourcing_milestone_id: 2
+      )
+      expect(Epic.find(2)).to have_attributes(
+        start_date: nil,
+        start_date_sourcing_milestone_id: nil,
+        due_date: Date.new(2000, 1, 30),
+        due_date_sourcing_milestone_id: 2
+      )
+      expect(Epic.find(3)).to have_attributes(
+        start_date: nil,
+        start_date_sourcing_milestone_id: nil,
+        due_date: nil,
+        due_date_sourcing_milestone_id: nil
+      )
+    end
+  end
+end