'Oracle doesn\'t support a database index on some data types.'

def check_field_type(self, field, field_type):

    errors = []
    if (field.db_index and (field_type.lower() in self.connection._limited_data_types)):
        errors.append(checks.Warning(('Oracle    does    not    support    a    database    index    on    %s    columns.' % field_type), hint="An    index    won't    be    created.    Silence    this    warning    if    you    don't    care    about    it.", obj=field, id='fields.W162'))
    return errors
