DB migration helper

migration_reversible.rb

module MigrationReversible
  def remove_existing_index(table_name, column_names, **options)
    index_name = options[:name]
    exists = suppress_messages { index_exists?(table_name, column_names, name: index_name) }

    reversible do |dir|
      dir.up { remove_index(table_name, name: index_name) if exists }
      dir.down do
        if exists
          say "existing index #{index_name.inspect} on table #{table_name.inspect}"
        else
          add_index(table_name, column_names, **options)
        end
      end
    end
  end

  def execute_when(up: nil, down: nil)
    reversible do |dir|
      dir.up { execute(up) } if up
      dir.down { execute(down) } if down
    end
  end
end