Merge branch 'index_on_iid' into 'master'

 Add uniq db index on project_id+iid

Because:
* its faster
* it solves problem with repeating iid's in one project

CHANGELOG

 v 6.9.0
   - Store Rails cache data in the Redis `cache:gitlab` namespace
   - Adjust MySQL limits for existing installations
+  - Add db index on project_id+iid column. This prevents duplicate on iid.
 
 v 6.8.0
   - Ability to at mention users that are participating in issue and merge req. discussion

app/models/milestone.rb

@@ -25,6 +25,7 @@ class Milestone < ActiveRecord::Base
 
   scope :active, -> { with_state(:active) }
   scope :closed, -> { with_state(:closed) }
+  scope :of_projects, ->(ids) { where(project_id: ids) }
 
   validates :title, presence: true
   validates :project, presence: true

db/migrate/20140416074002_add_index_on_iid.rb

+class AddIndexOnIid < ActiveRecord::Migration
+  def change
+    RemoveDuplicateIid.clean(Issue)
+    RemoveDuplicateIid.clean(MergeRequest, 'target_project_id')
+    RemoveDuplicateIid.clean(Milestone)
+
+    add_index :issues, [:project_id, :iid], unique: true
+    add_index :merge_requests, [:target_project_id, :iid], unique: true
+    add_index :milestones, [:project_id, :iid], unique: true
+  end
+end
+
+class RemoveDuplicateIid
+  def self.clean(klass, project_field = 'project_id')
+    duplicates = klass.find_by_sql("SELECT iid, #{project_field} FROM #{klass.table_name} GROUP BY #{project_field}, iid HAVING COUNT(*) > 1")
+
+    duplicates.each do |duplicate|
+      project_id = duplicate.send(project_field)
+      iid = duplicate.iid
+      items = klass.of_projects(project_id).where(iid: iid)
+
+      if items.size > 1
+        puts "Remove #{klass.name} duplicates for iid: #{iid} and project_id: #{project_id}"
+        items.shift
+        items.each do |item|
+          item.destroy
+          puts '.'
+        end
+      end
+    end
+  end
+end

db/schema.rb

@@ -93,6 +93,7 @@ ActiveRecord::Schema.define(version: 20140416185734) do
   add_index "issues", ["author_id"], name: "index_issues_on_author_id", using: :btree
   add_index "issues", ["created_at"], name: "index_issues_on_created_at", using: :btree
   add_index "issues", ["milestone_id"], name: "index_issues_on_milestone_id", using: :btree
+  add_index "issues", ["project_id", "iid"], name: "index_issues_on_project_id_and_iid", unique: true, using: :btree
   add_index "issues", ["project_id"], name: "index_issues_on_project_id", using: :btree
   add_index "issues", ["title"], name: "index_issues_on_title", using: :btree
 
@@ -143,6 +144,7 @@ ActiveRecord::Schema.define(version: 20140416185734) do
   add_index "merge_requests", ["source_branch"], name: "index_merge_requests_on_source_branch", using: :btree
   add_index "merge_requests", ["source_project_id"], name: "index_merge_requests_on_source_project_id", using: :btree
   add_index "merge_requests", ["target_branch"], name: "index_merge_requests_on_target_branch", using: :btree
+  add_index "merge_requests", ["target_project_id", "iid"], name: "index_merge_requests_on_target_project_id_and_iid", unique: true, using: :btree
   add_index "merge_requests", ["title"], name: "index_merge_requests_on_title", using: :btree
 
   create_table "milestones", force: true do |t|
@@ -157,6 +159,7 @@ ActiveRecord::Schema.define(version: 20140416185734) do
   end
 
   add_index "milestones", ["due_date"], name: "index_milestones_on_due_date", using: :btree
+  add_index "milestones", ["project_id", "iid"], name: "index_milestones_on_project_id_and_iid", unique: true, using: :btree
   add_index "milestones", ["project_id"], name: "index_milestones_on_project_id", using: :btree
 
   create_table "namespaces", force: true do |t|