Hello, Thanks for the link :) I think the documentation would be better structured, then, if https://docs.djangoproject.com/fr/4.0/ref/models/querysets/ would reference your link.
I have not read all of Django documentation. I do not know if it is expected that most developers would read everything. Hence, I learn using Google top ranked pages inside Django documentation when I search for a narrow topic on Django. If I search django prefetch django prefetching django prefetch_related django prefetch_related_objets I have https://docs.djangoproject.com/fr/4.0/ref/models/querysets/ as first result but your link does not appear. If I search django cache django caching I get this https://docs.djangoproject.com/fr/4.0/topics/cache/ but also your link as the third answer of Google. Maybe, adding a link to /topics/db/optimization from ref/models/querysets/ would help Google and people like me find this information more easily :) Best regards, Laurent Lyaudet Le ven. 24 juin 2022 à 08:05, Jason <[email protected]> a écrit : > > > This is explicitly called out in the documentation at > https://docs.djangoproject.com/en/4.0/topics/db/optimization/#understand-queryset-evaluation > On Thursday, June 23, 2022 at 1:17:50 PM UTC-4 [email protected] wrote: >> >> Hello, >> >> I made a simple test to check the number of queries done : >> >> # First part >> order = Order.objects.get(id=22222) # one query >> items = list(order.items.all()) # one query >> items = list(order.items.all()) # one query >> items = list(order.items.all()) # one query >> >> # Second part >> order = Order.objects.prefetch_related("items").get(id=22222) # two queries >> items = list(order.items.all()) # no query >> items = list(order.items.all()) # no query >> items = list(order.items.all()) # no query >> >> # Third part >> order = Order.objects.get(id=22222) # one query >> prefetch_related_objects([order], "items") # one query >> items = list(order.items.all()) # no query >> items = list(order.items.all()) # no query >> items = list(order.items.all()) # no query >> prefetch_related_objects([order], "items") # no more query >> prefetch_related_objects([order], "items") # no more query >> >> I was surprised that there was 4 queries for the First part of the test >> instead of 2 for the other parts, because I was expecting that .all() would >> also fill the cache and not only use it. >> Maybe it is intended. >> I think that this test or something else explaining this point could enhance >> the documentation on prefetch_related() and prefetch_related_objects(). >> I advised my colleagues to use prefetch_related_objects() when in doubt >> whether the objects given have been already extended with prefetching. >> >> Best regards, >> Laurent Lyaudet >> >> >> >> > -- > You received this message because you are subscribed to a topic in the Google > Groups "Django users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/django-users/CLnzKAcrE-A/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/01353b97-2b21-4d52-aab7-3046f93a5e1dn%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CAB1LBmssEnOGAAiKJDdLbL226oguyryJTkMUsKNYLTg1%3D89Urg%40mail.gmail.com.
