>>> len(connection.queries)
44
>>> lista = []
>>> ordens = Ordered.objects.all()
>>> for ordem in ordens:
...     for o in ordem.dealership.all():
...         lista.append(o.dealership)
...
>>> lista
[u'd1', u'd2', u'd2', u'd3', u'd1', u'd3', u'd2']
>>> len(connection.queries)
49
>>> lista = []
>>> ordens = Ordered.objects.all().prefetch_related('dealership')
>>> for ordem in ordens:
...     for o in ordem.dealership.all():
...         lista.append(o.dealership)
...
>>> lista
[u'd1', u'd2', u'd2', u'd3', u'd1', u'd3', u'd2']
>>> len(connection.queries)
51