#26491: Duplicated queries with nested prefetch ----------------------------------------------+-------------------- Reporter: duduklein | Owner: nobody Type: Uncategorized | Status: new Component: Database layer (models, ORM) | Version: 1.9 Severity: Normal | Keywords: Triage Stage: Unreviewed | Has patch: 0 Easy pickings: 0 | UI/UX: 0 ----------------------------------------------+-------------------- This ticket may be related to #26318 , but it's not the same since it does not involve repeated models.
Consider the following 3 test models: {{{ class Test1(models.Model): pass class Test2(models.Model): test1 = models.ForeignKey(Test1, related_name="tests2") class Test3(models.Model): test2 = models.ForeignKey(Test2, related_name="tests3") }}} Through the shell, we create initial entries and run the nested prefetch queries. We verify that the last 2 queries are duplicated: {{{ from test.models import Test1, Test2, test3 from django.db import connection from django.db.models import Prefetch t1 = Test1.objects.create() t2 = Test2.objects.create(test1 = t1) t3 = Test3.objects.create(test2 = t2) connection.queries_log.clear() tests2_prefetch = Prefetch("tests2", Test2.objects.prefetch_related("tests3")) Test1.objects.prefetch_related(tests2_prefetch) assert len(connection.queries) == 4 assert connection.queries[-1] == connection.queries[-2] }}} We had 4 queries instead of 3 expected and the last 2 are duplicated (to prefetch Test3 entries). -- Ticket URL: <https://code.djangoproject.com/ticket/26491> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To post to this group, send email to django-updates@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/052.d3b71c38ebab04c1490bda0b6ef4c816%40djangoproject.com. For more options, visit https://groups.google.com/d/optout.