only_example.py

# retrieving products with all fields
%timeit Product.objects.all()                                                                                                                                                                                                                        
6.08 µs ± 97.2 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)

# loading products with only upc column
%timeit Product.objects.only('upc')                                                                                                                                                                                                                  
15.4 µs ± 117 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)


# more about 'only()'
# this only loads upc and ignores earlier calls
Product.objects.only("name", "stock").only("upc")

# only and defer combined - this loads only upcs column immediately
Product.objects.only("name", "upc").defer("name")

# loads upc and name immediately as only() replaces any existing set of fields
Product.objects.defer("name").only("upc", "name")