Move foreign key to separate migration

db/migrate/20170217151948_add_owner_id_to_triggers.rb

@@ -5,6 +5,5 @@ class AddOwnerIdToTriggers < ActiveRecord::Migration
 
   def change
     add_column :ci_triggers, :owner_id, :integer
-    add_foreign_key :ci_triggers, :users, column: :owner_id, on_delete: :cascade
   end
 end

db/migrate/20170305203726_add_owner_id_foreign_key.rb

+class AddOwnerIdForeignKey < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def change
+    add_concurrent_foreign_key :ci_triggers, :users, column: :owner_id, on_delete: :cascade
+  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: 20170217151949) do
+ActiveRecord::Schema.define(version: 20170305203726) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -1335,7 +1335,7 @@ ActiveRecord::Schema.define(version: 20170217151949) do
   add_index "web_hooks", ["project_id"], name: "index_web_hooks_on_project_id", using: :btree
 
   add_foreign_key "boards", "projects"
-  add_foreign_key "ci_triggers", "users", column: "owner_id", on_delete: :cascade
+  add_foreign_key "ci_triggers", "users", column: "owner_id", name: "fk_e8e10d1964", on_delete: :cascade
   add_foreign_key "issue_metrics", "issues", on_delete: :cascade
   add_foreign_key "label_priorities", "labels", on_delete: :cascade
   add_foreign_key "label_priorities", "projects", on_delete: :cascade