Guard the EE migration because upgrading from

CE to EE could already have run the CE migration,
making these migrations not useful anymore.

ee/db/migrate/20170718185922_add_group_id_to_boards.rb

@@ -2,12 +2,16 @@ class AddGroupIdToBoards < ActiveRecord::Migration
   DOWNTIME = false
 
   def up
+    return if group_id_exists?
+
     change_column_null :boards, :project_id, true
 
     add_column :boards, :group_id, :integer
   end
 
   def down
+    return unless group_id_exists?
+
     # We cannot rollback project_id not null constraint if there are records
     # with null values.
     execute "DELETE from boards WHERE project_id IS NULL"
@@ -15,4 +19,10 @@ class AddGroupIdToBoards < ActiveRecord::Migration
     remove_column :boards, :group_id
     change_column :boards, :project_id, :integer, null: false
   end
+
+  private
+
+  def group_id_exists?
+    column_exists?(:boards, :group_id)
+  end
 end

ee/db/migrate/20170718190627_add_group_boards_indexes.rb

@@ -6,14 +6,26 @@ class AddGroupBoardsIndexes < ActiveRecord::Migration
   DOWNTIME = false
 
   def up
+    return if foreign_key_exists?(:boards, :group_id)
+
     add_concurrent_foreign_key :boards, :namespaces, column: :group_id, on_delete: :cascade
 
     add_concurrent_index :boards, :group_id
   end
 
   def down
+    return unless foreign_key_exists?(:boards, :group_id)
+
     remove_foreign_key :boards, column: :group_id
 
     remove_concurrent_index :boards, :group_id
   end
+
+  private
+
+  def foreign_key_exists?(table, column)
+    foreign_keys(table).any? do |key|
+      key.options[:column] == column.to_s
+    end
+  end
 end