'Return records to prefetch that have no value in cache for ``field``
(:class:`Field` instance), including ``self``.
Return at most ``limit`` records.'

@api.model
def _in_cache_without(self, field, limit=PREFETCH_MAX):

    ids = filter(None, (self._prefetch[self._name] - set(self.env.cache[field])))
    recs = self.browse(ids)
    if (limit and (len(recs) > limit)):
        recs = (self + (recs - self)[:(limit - len(self))])
    return recs
