Commit d5c7f9ef authored by Anssi Kääriäinen's avatar Anssi Kääriäinen
Browse files

Fixed #18304 -- Optimized save() when update_can_self_select=False 

Databases with update_can_self_select = False (MySQL for example)
generated non-necessary queries when saving a multitable inherited
model, and when the save resulted in update.
parent 6219591f

django/db/models/sql/compiler.py

+6 −0
Original line number Diff line number Diff line
@@ -1015,6 +1015,12 @@ class SQLUpdateCompiler(SQLCompiler): 
        query.extra = {}

        query.select = []

        query.add_fields([query.model._meta.pk.name])

        # Recheck the count - it is possible that fiddling with the select

        # fields above removes tables from the query. Refs #18304.

        count = query.count_active_tables()

        if not self.query.related_updates and count == 1:

            return



        must_pre_select = count > 1 and not self.connection.features.update_can_self_select



        # Now we adjust the current query: reset the where clause and get rid

tests/modeltests/model_inheritance/tests.py

+18 −0
Original line number Diff line number Diff line
@@ -275,3 +275,21 @@ class ModelInheritanceTests(TestCase): 
    def test_mixin_init(self):

        m = MixinModel()

        self.assertEqual(m.other_attr, 1)



    def test_update_query_counts(self):

        """

        Test that update queries do not generate non-necessary queries.

        Refs #18304.

        """

        c = Chef.objects.create(name="Albert")

        ir = ItalianRestaurant.objects.create(

            name="Ristorante Miron",

            address="1234 W. Ash",

            serves_hot_dogs=False,

            serves_pizza=False,

            serves_gnocchi=True,

            rating=4,

            chef=c

        )

        with self.assertNumQueries(6):

            ir.save()

tests/modeltests/update_only_fields/tests.py

+1 −4
Original line number Diff line number Diff line 
from __future__ import absolute_import



from django.test import TestCase, skipUnlessDBFeature

from django.test import TestCase

from django.db.models.signals import pre_save, post_save

from .models import Person, Employee, ProxyEmployee, Profile, Account
@@ -123,9 +123,6 @@ class UpdateOnlyFieldsTests(TestCase): 
        self.assertEqual(len(pre_save_data), 0)

        self.assertEqual(len(post_save_data), 0)



    # A bug in SQLUpdateCompiler prevents this test from succeeding on MySQL

    # Require update_can_self_select for this test for now. Refs #18304.

    @skipUnlessDBFeature('update_can_self_select')

    def test_num_queries_inheritance(self):

        s = Employee.objects.create(name='Sara', gender='F')

        s.employee_num = 1