Ticket #4102: 4102_Django1.3_JL20110610.patch

django/db/models/base.py

@@ -275 +275 @@
     def __init__(self, *args, **kwargs):
         signals.pre_init.send(sender=self.__class__, args=args, kwargs=kwargs)
 
+        self._reset_modified_attrs()
+
         # Set up the storage for instance state
         self._state = ModelState()
 
         # There is a rather weird disparity here; if kwargs, it's set, then args
-        # overrides it. It should be one or the other; don't duplicate the work
+        # overrides it. It should be one or the other; don't duplicate the work.
         # The reason for the kwargs check is that standard iterator passes in by
         # args, and instantiation for iteration is 33% faster.
         args_len = len(args)
@@ -365 +367 @@
         super(Model, self).__init__()
         signals.post_init.send(sender=self.__class__, instance=self)
 
+    def __setattr__(self, name, value):
+        if name not in self.__dict__.setdefault('_modified_attrs', []):
+            if not hasattr(self, name) or value != getattr(self, name):
+                self._modified_attrs.append(name)
+        super(Model, self).__setattr__(name, value)
+
+    def _reset_modified_attrs(self):
+        self.__dict__['_modified_attrs'] = []
+
     def __repr__(self):
         try:
             u = unicode(self)
@@ -523 +534 @@
                     # It does already exist, so do an UPDATE.
                     if force_update or non_pks:
                         values = [(f, None, (raw and getattr(self, f.attname) or f.pre_save(self, False))) for f in non_pks]
+
+                        # Only keep modified_attrs and those whose value has changed after pre_save
+                        if self._state.db == using:
+                            modified_attrs = self._modified_attrs
+                            values = [v for v in values
+                                      if v[0].name in modified_attrs or v[0].attname in modified_attrs or
+                                      v[2] != getattr(self, v[0].name)]
                         rows = manager.using(using).filter(pk=pk_val)._update(values)
                         if force_update and not rows:
                             raise DatabaseError("Forced update did not affect any rows.")
@@ -559 +577 @@
                     setattr(self, meta.pk.attname, result)
             transaction.commit_unless_managed(using=using)
 
+            self._reset_modified_attrs()
+
         # Store the database on which the object was saved
         self._state.db = using
         # Once saved, this is no longer a to-be-added instance.

django/db/models/query.py

@@ -284 +284 @@
                 else:
                     # Omit aggregates in object creation.
                     obj = model(*row[index_start:aggregate_start])
+                    # Models keep a track of modified attrs to choose which
+                    # fields to save. Since we're just pulling from the
+                    # database, nothing has changed yet.
+                    obj._reset_modified_attrs()
 
                 # Store the source database of the object
                 obj._state.db = db

tests/regressiontests/update_fields/models.py

@@ +1 @@
+"""
+Save only modified fields on update
+"""
+from django.db import models
+
+class Article(models.Model):
+    headline = models.CharField(max_length=100, default='Default headline')
+    body = models.TextField()
+    pub_date = models.DateTimeField()
+    modify_date = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        ordering = ('pub_date','headline')
+
+    def __str__(self):
+        return self.headline

tests/regressiontests/update_fields/tests.py

@@ +1 @@
+from datetime import datetime
+
+from django.test import TestCase
+
+from models import Article
+
+
+class UpdateFieldsTest(TestCase):
+
+    def test_basic_update_fields(self):
+        # Create a couple of Articles.
+        a = Article(headline=u'Article 1', body=u'Body 1', pub_date=datetime(2007, 5, 5))
+        a.save()
+
+        # Change headline and body on different instances, then save both to
+        # verify that each only updated the modified field.
+        a1 = Article.objects.get(pk=a.id)
+        a2 = Article.objects.get(pk=a.id)
+        a1.headline = u'Changed article 1'
+        a2.body = u'Changed body 1'
+        a1.save()
+        a2.save()
+
+        # The pre_save method should change the new modify_date of a1 and a2
+        self.assertNotEqual(a1.modify_date, a2.modify_date)
+        
+        a3 = Article.objects.get(pk=a.id)
+        self.assertEqual(a3.headline, u'Changed article 1')
+        self.assertEqual(a3.body, u'Changed body 1')
+        self.assertEqual(a3.modify_date, a2.modify_date)
+
+        # Fields entered at instantiation of a model which will already exists
+        # should be saved as well.
+        a = Article(id=a.id, headline=u'Reset article 1', body=u'Reset body 1', pub_date=datetime(2007, 5, 5))
+        a.save()
+        a3 = Article.objects.get(pk=a.id)
+        self.assertEqual(a3.headline, u'Reset article 1')
+        self.assertEqual(a3.body, u'Reset body 1')
+
+        # If the value doesn't change, it won't be marked as modified --
+        # otherwise user input like forms/etc is going to mark everything
+        # modified regardless.
+        a1 = Article.objects.get(pk=a.id)
+        a2 = Article.objects.get(pk=a.id)
+        a1.headline = u'Changed article 2'
+        a2.headline = a2.headline
+        a2.body = u'Changed body 2'
+        a1.save()
+        a2.save()
+        a3 = Article.objects.get(pk=a.id)
+        self.assertEqual(a3.headline, u'Changed article 2')
+        self.assertEqual(a3.body, u'Changed body 2')