text: from django.contrib.postgres.signals import (
      get_citext_oids, get_hstore_oids, register_type_handlers,
  )
  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" % schema_editor.quote_name(self.name))
          # Clear cached, stale oids.
          get_hstore_oids.cache_clear()
          get_citext_oids.cache_clear()
          # Registering new type handlers cannot be done before the extension is
          # installed, otherwise a subsequent data migration would use the same
          # connection.
          register_type_handlers(schema_editor.connection)
  
      def database_backwards(self, app_label, schema_editor, from_state, to_state):
          schema_editor.execute("DROP EXTENSION %s" % schema_editor.quote_name(self.name))
          # Clear cached, stale oids.
          get_hstore_oids.cache_clear()
          get_citext_oids.cache_clear()
  
      def describe(self):
          return "Creates extension %s" % self.name
  
  
  class BtreeGinExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'btree_gin'
  
  
  class BtreeGistExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'btree_gist'
  
  
  class CITextExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'citext'
  
  
  class CryptoExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'pgcrypto'
  
  
  class HStoreExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'hstore'
  
  
  class TrigramExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'pg_trgm'
  
  
  class UnaccentExtension(CreateExtension):
  
      def __init__(self):
          self.name = 'unaccent'
  