Merge branch 'add-index-to-approvals-mr-id' into 'master'

Add index to approvals.merge_request_id

Closes #2229

See merge request !1695

changelogs/unreleased-ee/add-index-to-approvals-mr-id.yml

+---
+title: Add index to approvals.merge_request_id
+merge_request:
+author:

db/migrate/20170421113144_add_index_to_approvals_merge_request_id.rb

+class AddIndexToApprovalsMergeRequestId < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :approvals, :merge_request_id
+  end
+
+  def down
+    remove_concurrent_index :approvals, :merge_request_id
+  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: 20170419065104) do
+ActiveRecord::Schema.define(version: 20170421113144) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -141,6 +141,8 @@ ActiveRecord::Schema.define(version: 20170419065104) do
     t.datetime "updated_at"
   end
 
+  add_index "approvals", ["merge_request_id"], name: "index_approvals_on_merge_request_id", using: :btree
+
   create_table "approver_groups", force: :cascade do |t|
     t.integer "target_id", null: false
     t.string "target_type", null: false