add index on CommunicationChannel.confirmation_code

Change-Id: Id277db73d6964eebdfdd5d76c1d0c7d4f015bad6
Reviewed-on: https://gerrit.instructure.com/23524
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

db/migrate/20130820210746_add_index_on_cccc.rb

@@ -0,0 +1,12 @@
+class AddIndexOnCccc < ActiveRecord::Migration
+  tag :postdeploy
+  self.transactional = false
+
+  def self.up
+    add_index :communication_channels, :confirmation_code, concurrently: true
+  end
+
+  def self.down
+    remove_index :communication_channels, :confirmation_code
+  end
+end