Why Django don't cache part of the result when the queryset is partly evaluated?

[胡凯旋]

As official document said, the code will query database twice.

>>> queryset = Entry.objects.all()
>>> print(queryset[5]) # Queries the database
>>> print(queryset[5]) # Queries the database again

 Why don't just cache the record at index 5 of this queryset? When execute queryset[5] again, fetch result from cache rather than database? 

Is there any reason don't cache results of queryset partly?