lookups.py 文件源码

def process_rhs(self, compiler, connection):
        value = self.rhs
        if self.bilateral_transforms:
            if self.rhs_is_direct_value():
                # Do not call get_db_prep_lookup here as the value will be
                # transformed before being used for lookup
                value = QueryWrapper("%s",
                    [self.lhs.output_field.get_db_prep_value(value, connection)])
            value = self.apply_bilateral_transforms(value)
        # Due to historical reasons there are a couple of different
        # ways to produce sql here. get_compiler is likely a Query
        # instance, _as_sql QuerySet and as_sql just something with
        # as_sql. Finally the value can of course be just plain
        # Python value.
        if hasattr(value, 'get_compiler'):
            value = value.get_compiler(connection=connection)
        if hasattr(value, 'as_sql'):
            sql, params = compiler.compile(value)
            return '(' + sql + ')', params
        if hasattr(value, '_as_sql'):
            sql, params = value._as_sql(connection=connection)
            return '(' + sql + ')', params
        else:
            return self.get_db_prep_lookup(value, connection)