Comment 1 for bug 1287708

Hmm in fact it is set. In the method itself:

        # We memoize allowed partner
        if not context.get('partner_memoizer'):
            context['partner_memoizer'] = tuple(self.pool['res.partner'].search(cr, uid, []))
        if not context['partner_memoizer']:
            return res

But I have some doubt on the efficiency of such a thing as anyway it always searches all the ids.