Add index to ahoy_messages to (#2367)

* Add index to ahoy_messages to

* Add ahoy_messages index concurrently

db/migrate/20190410124957_add_index_to_ahoy_messages_to.rb

@@ -0,0 +1,7 @@
+class AddIndexToAhoyMessagesTo < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_index :ahoy_messages, :to, algorithm: :concurrently
+  end
+end

db/schema.rb

@@ -33,6 +33,7 @@ ActiveRecord::Schema.define(version: 2019_07_23_094834) do
     t.string "utm_medium"
     t.string "utm_source"
     t.string "utm_term"
+    t.index ["to"], name: "index_ahoy_messages_on_to"
     t.index ["token"], name: "index_ahoy_messages_on_token"
     t.index ["user_id", "user_type"], name: "index_ahoy_messages_on_user_id_and_user_type"
   end