edits

Author: timgraham

django_mongodb_backend/cache.py

@@ -14,8 +14,9 @@ def __init__(self, protocol=None):
         self.protocol = pickle.HIGHEST_PROTOCOL if protocol is None else protocol
 
     def dumps(self, obj):
-        # Only skip pickling for integers, a int subclasses as bool should be
-        # pickled.
+        # For better incr() and decr() atomicity, don't pickle integers.
+        # Using type() rather than isinstance() matches only integers and not
+        # subclasses like bool.
         if type(obj) is int:  # noqa: E721
             return obj
         return pickle.dumps(obj, self.protocol)
@@ -59,10 +60,7 @@ def collection_for_write(self):
         return connections[db].get_collection(self._collection_name)
 
     def get(self, key, default=None, version=None):
-        result = self.get_many([key], version)
-        if result:
-            return result[key]
-        return default
+        return self.get_many([key], version).get(key, default)
 
     def _filter_expired(self, expired=False):
         not_expired_filter = [{"expires_at": {"$gte": datetime.utcnow()}}, {"expires_at": None}]
@@ -80,7 +78,6 @@ def get_many(self, keys, version=None):
 
     def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_and_validate_key(key, version=version)
-        serialized_data = self.serializer.dumps(value)
         num = self.collection_for_write.count_documents({}, hint="_id_")
         if num >= self._max_entries:
             self._cull(num)
@@ -89,16 +86,15 @@ def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
             {
                 "$set": {
                     "key": key,
-                    "value": serialized_data,
+                    "value": self.serializer.dumps(value),
                     "expires_at": self._get_expiration_time(timeout),
                 }
             },
-            True,
+            upsert=True,
         )
 
     def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_and_validate_key(key, version=version)
-        serialized_data = self.serializer.dumps(value)
         num = self.collection_for_write.count_documents({}, hint="_id_")
         if num >= self._max_entries:
             self._cull(num)
@@ -108,11 +104,11 @@ def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
                 {
                     "$set": {
                         "key": key,
-                        "value": serialized_data,
+                        "value": self.serializer.dumps(value),
                         "expires_at": self._get_expiration_time(timeout),
                     }
                 },
-                True,
+                upsert=True,
             )
         except DuplicateKeyError:
             return False
@@ -171,7 +167,8 @@ def incr(self, key, delta=1, version=None):
                 return_document=ReturnDocument.AFTER,
             )
         except OperationFailure as ex:
-            raise TypeError("Cannot apply incr to a value of non-numeric type") from ex
+            method_name = "incr" if delta >= 1 else "decr"
+            raise TypeError(f"Cannot apply {method_name}() to a value of non-numeric type.") from ex
         # Not exists
         if updated is None:
             raise ValueError(f"Key '{key}' not found.") from None

django_mongodb_backend/creation.py

@@ -1,8 +1,9 @@
 from django.conf import settings
-from django.core.cache import caches
 from django.db.backends.base.creation import BaseDatabaseCreation
 
-from django_mongodb_backend.cache import MongoDBCache
+from django_mongodb_backend.management.commands.createcachecollection import (
+    Command as CreateCacheCollection,
+)
 
 
 class DatabaseCreation(BaseDatabaseCreation):
@@ -22,12 +23,9 @@ def _destroy_test_db(self, test_database_name, verbosity):
 
     def create_test_db(self, *args, **kwargs):
         test_database_name = super().create_test_db(*args, **kwargs)
-        # Create cache collections
-        for cache_alias in settings.CACHES:
-            cache = caches[cache_alias]
-            if isinstance(cache, MongoDBCache):
-                connection = cache._db_to_write
-                if cache._collection_name in connection.introspection.table_names():
-                    continue
-                cache.create_indexes()
+        # Not using call_command() avoids the requirement to put
+        # "django_mongodb_backend" in INSTALLED_APPS.
+        CreateCacheCollection().handle(
+            database=self.connection.alias, verbosity=kwargs["verbosity"]
+        )
         return test_database_name

docs/source/releases/5.1.x.rst

@@ -2,6 +2,13 @@
 Django MongoDB Backend 5.1.x
 ============================
 
+5.1.0 beta 2
+============
+
+*Unreleased*
+
+- Added support for :doc:`database caching </topics/cache>`.
+
 5.1.0 beta 1
 ============
 

tests/cache_/tests.py

@@ -1,3 +1,4 @@
+"""These tests are forked from Django's tests/cache/tests.py."""
 import os
 import pickle
 import time
@@ -9,13 +10,8 @@
 from django.core import management
 from django.core.cache import DEFAULT_CACHE_ALIAS, CacheKeyWarning, cache, caches
 from django.core.cache.backends.base import InvalidCacheBackendError
-from django.http import (
-    HttpResponse,
-)
-from django.middleware.cache import (
-    FetchFromCacheMiddleware,
-    UpdateCacheMiddleware,
-)
+from django.http import HttpResponse
+from django.middleware.cache import FetchFromCacheMiddleware, UpdateCacheMiddleware
 from django.test import RequestFactory, TestCase, modify_settings, override_settings
 
 from .models import Poll, expensive_calculation
@@ -97,12 +93,8 @@ def caches_setting_for_tests(base=None, exclude=None, **params):
 
 
 class BaseCacheTests:
-    # A common set of tests to apply to all cache backends
     factory = RequestFactory()
-
-    # Some clients raise custom exceptions when .incr() or .decr() are called
-    # with a non-integer value.
-    incr_decr_type_error = TypeError
+    incr_decr_type_error_msg = "Cannot apply %s() to a value of non-numeric type."
 
     def tearDown(self):
         cache.clear()
@@ -186,12 +178,12 @@ def test_incr(self):
         self.assertEqual(cache.incr("answer", 10), 52)
         self.assertEqual(cache.get("answer"), 52)
         self.assertEqual(cache.incr("answer", -10), 42)
-        with self.assertRaises(ValueError):
+        with self.assertRaisesMessage(ValueError, "Key 'does_not_exist' not found."):
             cache.incr("does_not_exist")
-        with self.assertRaises(ValueError):
+        with self.assertRaisesMessage(ValueError, "Key 'does_not_exist' not found."):
             cache.incr("does_not_exist", -1)
         cache.set("null", None)
-        with self.assertRaises(self.incr_decr_type_error):
+        with self.assertRaisesMessage(TypeError, self.incr_decr_type_error_msg % "incr"):
             cache.incr("null")
 
     def test_decr(self):
@@ -202,12 +194,12 @@ def test_decr(self):
         self.assertEqual(cache.decr("answer", 10), 32)
         self.assertEqual(cache.get("answer"), 32)
         self.assertEqual(cache.decr("answer", -10), 42)
-        with self.assertRaises(ValueError):
+        with self.assertRaisesMessage(ValueError, "Key 'does_not_exist' not found."):
             cache.decr("does_not_exist")
-        with self.assertRaises(ValueError):
+        with self.assertRaisesMessage(ValueError, "Key 'does_not_exist' not found."):
             cache.incr("does_not_exist", -1)
         cache.set("null", None)
-        with self.assertRaises(self.incr_decr_type_error):
+        with self.assertRaisesMessage(TypeError, self.incr_decr_type_error_msg % "decr"):
             cache.decr("null")
 
     def test_close(self):
@@ -846,12 +838,7 @@ def test_custom_key_func(self):
         self.assertEqual(caches["custom_key"].get("answer2"), 42)
         self.assertEqual(caches["custom_key2"].get("answer2"), 42)
 
-    @override_settings(
-        CACHE_MIDDLEWARE_ALIAS=DEFAULT_CACHE_ALIAS,
-    )
-    @modify_settings(
-        INSTALLED_APPS={"prepend": "django_mongodb_backend"},
-    )
+    @override_settings(CACHE_MIDDLEWARE_ALIAS=DEFAULT_CACHE_ALIAS)
     def test_cache_write_unpicklable_object(self):
         fetch_middleware = FetchFromCacheMiddleware(empty_response)
 
@@ -1003,7 +990,7 @@ def allow_migrate(self, db, app_label, **hints):
 @modify_settings(
     INSTALLED_APPS={"prepend": "django_mongodb_backend"},
 )
-class CreateCacheTableForDBCacheTests(TestCase):
+class CreateCacheCollectionTests(TestCase):
     databases = {"default", "other"}
 
     @override_settings(DATABASE_ROUTERS=[DBCacheRouter()])