Ticket #3615: allow_forward_refs_in_fixtures_v2.diff

tests/regressiontests/fixtures_regress/fixtures/forward_ref_bad_data.json

@@ +1 @@
+[
+    {
+        "pk": 1,
+        "model": "fixtures_regress.book",
+        "fields": {
+            "name": "Cryptonomicon",
+            "author": 3
+        }
+    },
+    {
+        "pk": "4",
+        "model": "fixtures_regress.person",
+        "fields": {
+            "name": "Neal Stephenson"
+        }
+    }
+]
+ No newline at end of file

tests/regressiontests/fixtures_regress/fixtures/forward_ref.json

@@ +1 @@
+[
+    {
+        "pk": 1,
+        "model": "fixtures_regress.book",
+        "fields": {
+            "name": "Cryptonomicon",
+            "author": 4
+        }
+    },
+    {
+        "pk": "4",
+        "model": "fixtures_regress.person",
+        "fields": {
+            "name": "Neal Stephenson"
+        }
+    }
+]
+ No newline at end of file

tests/regressiontests/fixtures_regress/tests.py

@@ -12 +12 @@
 from django.core.management.commands.dumpdata import sort_dependencies
 from django.core.management.base import CommandError
 from django.db.models import signals
-from django.db import transaction
+from django.db import transaction, IntegrityError
 from django.test import TestCase, TransactionTestCase, skipIfDBFeature, \
     skipUnlessDBFeature
 
@@ -362 +362 @@
             """[{"pk": %d, "model": "fixtures_regress.widget", "fields": {"name": "grommet"}}]"""
             % widget.pk
             )
+    
+    def test_loaddata_works_when_fixture_has_forward_refs(self):
+        """
+        Regression for #3615 - Forward references cause fixtures not to load in MySQL (InnoDB)
+        """
+        management.call_command(
+            'loaddata',
+            'forward_ref.json',
+            verbosity=0,
+            commit=False
+        )
+        self.assertEqual(Book.objects.all()[0].id, 1)
+        self.assertEqual(Person.objects.all()[0].id, 4)
+    
+    def test_loaddata_raise_when_fixture_has_forward_refs(self):
+        """
+        Regression for #3615 - Ensure data with nonexistent child key references raises error
+        """
+        stderr = StringIO()
+        management.call_command(
+            'loaddata',
+            'forward_ref_bad_data.json',
+            verbosity=0,
+            commit=False,
+            stderr=stderr,
+        )
+        self.assertTrue(
+            stderr.getvalue().startswith('Problem installing fixture')
+        )
 
 
 class NaturalKeyFixtureTests(TestCase):

django/db/backends/mysql/base.py

@@ -25 +25 @@
 from MySQLdb.converters import conversions
 from MySQLdb.constants import FIELD_TYPE, CLIENT
 
-from django.db import utils
+from django.db import utils, IntegrityError
 from django.db.backends import *
 from django.db.backends.signals import connection_created
 from django.db.backends.mysql.client import DatabaseClient
@@ -349 +349 @@
                 raise Exception('Unable to determine MySQL version from version string %r' % self.connection.get_server_info())
             self.server_version = tuple([int(x) for x in m.groups()])
         return self.server_version
+
+    def begin_defer_constraint_checks(self):
+        self.foreign_key_checks_disabled = True
+        self.cursor().execute('SET foreign_key_checks=0')
+
+    def end_defer_constraint_checks(self):
+        self.foreign_key_checks_disabled = False
+        self.cursor().execute('SET foreign_key_checks=1')
+    
+    def check_foreign_key_constraints_for_table(self, table_name):
+        cursor = self.cursor()
+        bad_rows = []
+        key_columns = self.introspection.get_key_columns(self.cursor(), table_name)
+        for column_name, referenced_table_name, referenced_column_name in key_columns:
+            cursor.execute("""
+                SELECT * FROM `%s` as REFERRING
+                LEFT JOIN `%s` as REFERRED
+                ON (REFERRING.`%s` = REFERRED.`%s`)
+                WHERE REFERRING.`%s` IS NOT NULL
+                    AND REFERRED.`%s` IS NULL
+                """ % (table_name, referenced_table_name, column_name, referenced_column_name, column_name, referenced_column_name))
+            bad_rows.extend(cursor.fetchall())
+        if bad_rows:
+            raise IntegrityError("Bad rows found.")

django/db/backends/mysql/introspection.py

@@ -51 +51 @@
         representing all relationships to the given table. Indexes are 0-based.
         """
         my_field_dict = self._name_to_index(cursor, table_name)
-        constraints = []
+        constraints = self.get_key_columns(cursor, table_name)
         relations = {}
+        for my_fieldname, other_table, other_field in constraints:
+            other_field_index = self._name_to_index(cursor, other_table)[other_field]
+            my_field_index = my_field_dict[my_fieldname]
+            relations[my_field_index] = (other_field_index, other_table)
+        return relations
+
+    def get_key_columns(self, cursor, table_name):
+        key_columns = []
         try:
             # This should work for MySQL 5.0.
             cursor.execute("""
@@ -62 +70 @@
                     AND table_schema = DATABASE()
                     AND referenced_table_name IS NOT NULL
                     AND referenced_column_name IS NOT NULL""", [table_name])
-            constraints.extend(cursor.fetchall())
+            key_columns.extend(cursor.fetchall())
         except (ProgrammingError, OperationalError):
             # Fall back to "SHOW CREATE TABLE", for previous MySQL versions.
             # Go through all constraints and save the equal matches.
@@ -74 +82 @@
                     if match == None:
                         break
                     pos = match.end()
-                    constraints.append(match.groups())
+                    key_columns.append(match.groups())
+        return key_columns
 
-        for my_fieldname, other_table, other_field in constraints:
-            other_field_index = self._name_to_index(cursor, other_table)[other_field]
-            my_field_index = my_field_dict[my_fieldname]
-            relations[my_field_index] = (other_field_index, other_table)
-
-        return relations
-
     def get_indexes(self, cursor, table_name):
         """
         Returns a dictionary of fieldname -> infodict for the given table,

django/db/backends/__init__.py

@@ -34 +34 @@
         self.transaction_state = []
         self.savepoint_state = 0
         self._dirty = None
+        
+        self.foreign_key_checks_disabled = False
 
     def __eq__(self, other):
         return self.alias == other.alias
@@ -239 +241 @@
         if self.savepoint_state:
             self._savepoint_commit(sid)
 
+    def begin_defer_constraint_checks(self):
+        return None
+
+    def end_defer_constraint_checks(self):
+        return None
+
     def close(self):
         if self.connection is not None:
             self.connection.close()

django/core/management/commands/loaddata.py

@@ -8 +8 @@
 from django.core import serializers
 from django.core.management.base import BaseCommand
 from django.core.management.color import no_style
-from django.db import connections, router, transaction, DEFAULT_DB_ALIAS
+from django.db import connections, router, transaction, DEFAULT_DB_ALIAS, models as db_models
 from django.db.models import get_apps
 from django.utils.itercompat import product
 
@@ -161 +161 @@
                             fixture_count += 1
                             objects_in_fixture = 0
                             loaded_objects_in_fixture = 0
+                            saved_objects = []
                             if verbosity >= 2:
                                 self.stdout.write("Installing %s fixture '%s' from %s.\n" % \
                                     (format, fixture_name, humanize(fixture_dir)))
                             try:
                                 objects = serializers.deserialize(format, fixture, using=using)
+                                connection.begin_defer_constraint_checks()
                                 for obj in objects:
                                     objects_in_fixture += 1
                                     if router.allow_syncdb(using, obj.object.__class__):
                                         loaded_objects_in_fixture += 1
                                         models.add(obj.object.__class__)
                                         obj.save(using=using)
+                                        saved_objects.append(obj.object)
+                                        
+                                # If we disabled foreign_key_checks, then re-enable them and save them all
+                                # again. This will expose any referential integrity errors.
+                                if connection.foreign_key_checks_disabled:
+                                    connection.end_defer_constraint_checks()
+                                    for model in models:
+                                        connection.check_foreign_key_constraints_for_table(table_name=model._meta.db_table)
+                                    
                                 loaded_object_count += loaded_objects_in_fixture
                                 fixture_object_count += objects_in_fixture
                                 label_found = True