text: from django.contrib.postgres.signals import register_hstore_handler
  from django.db.migrations.operations.base import Operation
  
  
  class CreateExtension(Operation):
      reversible = True
  
      def __init__(self, name):
          self.name = name
  
      def state_forwards(self, app_label, state):
          pass
  
      def database_forwards(self, app_label, schema_editor, from_state, to_state):
          if schema_editor.connection.vendor != 'postgresql':
              return
          schema_editor.execute("CREATE EXTENSION IF NOT EXISTS %s" % self.name)
  
      def database_backwards(self, app_label, schema_editor, from_state, to_state):
          schema_editor.execute("DROP EXTENSION %s" % self.name)
  
      def describe(self):
          return "Creates extension %s" % self.name
  
  
  class HStoreExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'hstore'
  
      def database_forwards(self, app_label, schema_editor, from_state, to_state):
          super(HStoreExtension, self).database_forwards(app_label, schema_editor, from_state, to_state)
          # Register hstore straight away as it cannot be done before the
          # extension is installed, a subsequent data migration would use the
          # same connection
          register_hstore_handler(schema_editor.connection)
  
  
  class UnaccentExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'unaccent'
  