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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/ref/models/querysets.txt | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/docs/ref/models/querysets.txt b/docs/ref/models/querysets.txt index a160587953..22ccda4b8e 100644 --- a/docs/ref/models/querysets.txt +++ b/docs/ref/models/querysets.txt @@ -989,6 +989,24 @@ less ambiguous than storing a filtered result in the related manager's cache: ... Prefetch('pizzas', queryset=queryset)) >>> vegetarian_pizzas = restaurants[0].pizzas.all() +Custom prefetching also works with single related relations like +forward ``ForeignKey`` or ``OneToOneField``. Generally you'll want to use +:meth:`select_related()` for these relations, but there are a number of cases +where prefetching with a custom ``QuerySet`` is useful: + +* You want to use a ``QuerySet`` that performs further prefetching + on related models. + +* You want to prefetch only a subset of the related objects. + +* You want to use performance optimization techniques like + :meth:`deferred fields <defer()>`: + + >>> queryset = Pizza.objects.only('name') + >>> + >>> restaurants = Restaurant.objects.prefetch_related( + ... Prefetch('best_pizza', queryset=queryset)) + .. note:: The ordering of lookups matters. |