Edits create_project_mirror_data to add the new columns when table already exists

db/migrate/20180502122856_create_project_mirror_data.rb

@@ -4,13 +4,17 @@ class CreateProjectMirrorData < ActiveRecord::Migration
   DOWNTIME = false
 
   def up
-    return if table_exists?(:project_mirror_data)
-
-    create_table :project_mirror_data do |t|
-      t.references :project, index: true, foreign_key: { on_delete: :cascade }
-      t.string :status
-      t.string :jid
-      t.text :last_error
+    if table_exists?(:project_mirror_data)
+      add_column :project_mirror_data, :status, :string unless column_exists?(:project_mirror_data, :status)
+      add_column :project_mirror_data, :jid, :string unless column_exists?(:project_mirror_data, :jid)
+      add_column :project_mirror_data, :last_error, :text unless column_exists?(:project_mirror_data, :last_error)
+    else
+      create_table :project_mirror_data do |t|
+        t.references :project, index: true, foreign_key: { on_delete: :cascade }
+        t.string :status
+        t.string :jid
+        t.text :last_error
+      end
     end
   end