Fixed #12118 -- Added shared cache support to SQLite in-memory testing.

django/db/backends/sqlite3/base.py

@@ -9,6 +9,7 @@ from __future__ import unicode_literals
 import datetime
 import decimal
 import re
+import sys
 import uuid
 import warnings
 
@@ -123,6 +124,14 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     def can_release_savepoints(self):
         return self.uses_savepoints
 
+    @cached_property
+    def can_share_in_memory_db(self):
+        return (
+            sys.version_info[:2] >= (3, 4) and
+            Database.__name__ == 'sqlite3.dbapi2' and
+            Database.sqlite_version_info >= (3, 7, 13)
+        )
+
     @cached_property
     def supports_stddev(self):
         """Confirm support for STDDEV and related stats functions
@@ -405,6 +414,8 @@ class DatabaseWrapper(BaseDatabaseWrapper):
                 RuntimeWarning
             )
         kwargs.update({'check_same_thread': False})
+        if self.features.can_share_in_memory_db:
+            kwargs.update({'uri': True})
         return kwargs
 
     def get_new_connection(self, conn_params):
@@ -429,7 +440,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         # If database is in memory, closing the connection destroys the
         # database. To prevent accidental data loss, ignore close requests on
         # an in-memory db.
-        if self.settings_dict['NAME'] != ":memory:":
+        if not self.is_in_memory_db(self.settings_dict['NAME']):
             BaseDatabaseWrapper.close(self)
 
     def _savepoint_allowed(self):
@@ -505,6 +516,9 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         """
         self.cursor().execute("BEGIN")
 
+    def is_in_memory_db(self, name):
+        return name == ":memory:" or "mode=memory" in name
+
 
 FORMAT_QMARK_REGEX = re.compile(r'(?<!%)%s')
 

django/db/backends/sqlite3/creation.py

@@ -1,6 +1,7 @@
 import os
 import sys
 
+from django.core.exceptions import ImproperlyConfigured
 from django.db.backends.creation import BaseDatabaseCreation
 from django.utils.six.moves import input
 
@@ -51,14 +52,22 @@ class DatabaseCreation(BaseDatabaseCreation):
     def _get_test_db_name(self):
         test_database_name = self.connection.settings_dict['TEST']['NAME']
         if test_database_name and test_database_name != ':memory:':
+            if 'mode=memory' in test_database_name:
+                raise ImproperlyConfigured(
+                    "Using `mode=memory` parameter in the database name is not allowed, "
+                    "use `:memory:` instead."
+                )
             return test_database_name
+        if self.connection.features.can_share_in_memory_db:
+            return 'file:memorydb_%s?mode=memory&cache=shared' % self.connection.alias
         return ':memory:'
 
     def _create_test_db(self, verbosity, autoclobber, keepdb=False):
         test_database_name = self._get_test_db_name()
+
         if keepdb:
             return test_database_name
-        if test_database_name != ':memory:':
+        if not self.connection.is_in_memory_db(test_database_name):
             # Erase the old test database
             if verbosity >= 1:
                 print("Destroying old test database '%s'..." % self.connection.alias)
@@ -80,7 +89,7 @@ class DatabaseCreation(BaseDatabaseCreation):
         return test_database_name
 
     def _destroy_test_db(self, test_database_name, verbosity):
-        if test_database_name and test_database_name != ":memory:":
+        if test_database_name and not self.connection.is_in_memory_db(test_database_name):
             # Remove the SQLite database file
             os.remove(test_database_name)
 
@@ -92,8 +101,8 @@ class DatabaseCreation(BaseDatabaseCreation):
         SQLite since the databases will be distinct despite having the same
         TEST NAME. See http://www.sqlite.org/inmemorydb.html
         """
-        test_dbname = self._get_test_db_name()
+        test_database_name = self._get_test_db_name()
         sig = [self.connection.settings_dict['NAME']]
-        if test_dbname == ':memory:':
+        if self.connection.is_in_memory_db(test_database_name):
             sig.append(self.connection.alias)
         return tuple(sig)

django/test/testcases.py

@@ -1212,8 +1212,7 @@ class LiveServerTestCase(TransactionTestCase):
         for conn in connections.all():
             # If using in-memory sqlite databases, pass the connections to
             # the server thread.
-            if (conn.vendor == 'sqlite'
+            if conn.vendor == 'sqlite' and conn.is_in_memory_db(conn.settings_dict['NAME']):
-                    and conn.settings_dict['NAME'] == ':memory:'):
                 # Explicitly enable thread-shareability for this connection
                 conn.allow_thread_sharing = True
                 connections_override[conn.alias] = conn
@@ -1267,10 +1266,9 @@ class LiveServerTestCase(TransactionTestCase):
             cls.server_thread.terminate()
             cls.server_thread.join()
 
-        # Restore sqlite connections' non-shareability
+        # Restore sqlite in-memory database connections' non-shareability
         for conn in connections.all():
-            if (conn.vendor == 'sqlite'
+            if conn.vendor == 'sqlite' and conn.is_in_memory_db(conn.settings_dict['NAME']):
-                    and conn.settings_dict['NAME'] == ':memory:'):
                 conn.allow_thread_sharing = False
 
     @classmethod

docs/releases/1.8.txt

@@ -573,6 +573,10 @@ Tests
 
 * Added test client support for file uploads with file-like objects.
 
+* A shared cache is now used when testing with a SQLite in-memory database when
+  using Python 3.4+ and SQLite 3.7.13+. This allows sharing the database
+  between threads.
+
 Validators
 ^^^^^^^^^^
 

docs/topics/testing/overview.txt

@@ -185,12 +185,20 @@ control the particular collation used by the test database. See the
 :doc:`settings documentation </ref/settings>` for details of these
 and other advanced settings.
 
+If using a SQLite in-memory database with Python 3.4+ and SQLite 3.7.13+,
+`shared cache <https://www.sqlite.org/sharedcache.html>`_ will be enabled, so
+you can write tests with ability to share the database between threads.
+
 .. versionchanged:: 1.7
 
    The different options in the :setting:`TEST <DATABASE-TEST>` database
    setting used to be separate options in the database settings dictionary,
    prefixed with ``TEST_``.
 
+.. versionadded:: 1.8
+
+    The ability to use SQLite with a shared cache as described above was added.
+
 .. admonition:: Finding data from your production database when running tests?
 
     If your code attempts to access the database when its modules are compiled,

tests/backends/tests.py

@@ -6,6 +6,7 @@ import copy
 import datetime
 from decimal import Decimal, Rounded
 import re
+import sys
 import threading
 import unittest
 import warnings
@@ -1201,3 +1202,21 @@ class DBTestSettingsRenamedTests(IgnoreAllDeprecationWarningsMixin, TestCase):
     def test_empty_settings(self):
         with override_settings(DATABASES=self.db_settings):
             self.handler.prepare_test_settings('default')
+
+
+@unittest.skipUnless(connection.vendor == 'sqlite', 'SQLite specific test.')
+@skipUnlessDBFeature('can_share_in_memory_db')
+class TestSqliteThreadSharing(TransactionTestCase):
+    available_apps = ['backends']
+
+    def test_database_sharing_in_threads(self):
+        def create_object():
+            models.Object.objects.create()
+
+        create_object()
+
+        thread = threading.Thread(target=create_object)
+        thread.start()
+        thread.join()
+
+        self.assertEqual(models.Object.objects.count(), 2)