Add CACHALOT_ADDITIONAL_TABLES for unmanaged models (#183)

* Add CACHALOT_ADDITIONAL_TABLES for unmanaged models
- Fixes #182
- For doc purposes, we do not want to use table_names and want to continue using django_table_names from connection.introspection to avoid a query to the db every request.

CHANGELOG.rst

@@ -9,6 +9,7 @@ What’s new in django-cachalot?
 - Drop support for Django 2.0-2.1 and Python 3.5 (#181)
 - Add support for Pymemcache for Django 3.2+ (#181)
 - Reverts #157 with proper fix. (#181)
+- Add ``CACHALOT_ADDITIONAL_TABLES`` setting for unmanaged models (#183)
 
 2.3.5
 -----

cachalot/settings.py

@@ -53,6 +53,7 @@ class Settings(object):
     CACHALOT_INVALIDATE_RAW = True
     CACHALOT_ONLY_CACHABLE_TABLES = ()
     CACHALOT_UNCACHABLE_TABLES = ('django_migrations',)
+    CACHALOT_ADDITIONAL_TABLES = ()
     CACHALOT_QUERY_KEYGEN = 'cachalot.utils.get_query_cache_key'
     CACHALOT_TABLE_KEYGEN = 'cachalot.utils.get_table_cache_key'
 
@@ -112,6 +113,11 @@ def convert(value):
     return frozenset(value)
 
 
+@Settings.add_converter('CACHALOT_ADDITIONAL_TABLES')
+def convert(value):
+    return list(value)
+
+
 @Settings.add_converter('CACHALOT_QUERY_KEYGEN')
 def convert(value):
     return import_string(value)

cachalot/tests/settings.py

@@ -11,7 +11,7 @@ from django.test.utils import override_settings
 
 from ..api import invalidate
 from ..settings import SUPPORTED_ONLY, SUPPORTED_DATABASE_ENGINES
-from .models import Test, TestParent, TestChild
+from .models import Test, TestParent, TestChild, UnmanagedModel
 from .test_utils import TestUtilsMixin
 
 
@@ -172,6 +172,14 @@ class SettingsTestCase(TestUtilsMixin, TransactionTestCase):
             self.assert_query_cached(TestParent.objects.all())
             self.assert_query_cached(User.objects.all(), after=1)
 
+    def test_uncachable_unmanaged_table(self):
+        qs = UnmanagedModel.objects.all()
+        with self.settings(
+            CACHALOT_UNCACHABLE_TABLES=("cachalot_unmanagedmodel",),
+            CACHALOT_ADDITIONAL_TABLES=("cachalot_unmanagedmodel",)
+        ):
+            self.assert_query_cached(qs, after=1)
+
     def test_cache_compatibility(self):
         compatible_cache = {
             'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',

cachalot/utils.py

@@ -97,7 +97,25 @@ def get_table_cache_key(db_alias, table):
 
 def _get_tables_from_sql(connection, lowercased_sql):
     return {t for t in connection.introspection.django_table_names()
-            if t in lowercased_sql}
+            + cachalot_settings.CACHALOT_ADDITIONAL_TABLES if t in lowercased_sql}
+
+
+def _find_rhs_lhs_subquery(side):
+    h_class = side.__class__
+    if h_class is Query:
+        return side
+    elif h_class is QuerySet:
+        return side.query
+    elif h_class in (Subquery, Exists):  # Subquery allows QuerySet & Query
+        try:
+            return side.query.query if side.query.__class__ is QuerySet else side.query
+        except AttributeError:  # TODO Remove try/except closure after drop Django 2.2
+            try:
+                return side.queryset.query
+            except AttributeError:
+                return None
+    elif h_class in UNCACHABLE_FUNCS:
+        raise UncachableQuery
 
 
 def _find_rhs_lhs_subquery(side):

docs/quickstart.rst

@@ -144,6 +144,16 @@ Settings
   some issues, especially during tests.
   Run ``./manage.py invalidate_cachalot`` after changing this setting.
 
+``CACHALOT_ADDITIONAL_TABLES``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+:Default: ``list()``
+:Description:
+  Sequence of SQL table names that are not included in your Django
+  apps such as unmanaged models. Cachalot caches models that Django
+  does not manage, so if you want to ignore/not-cache those models,
+  then add them here.
+
 ``CACHALOT_QUERY_KEYGEN``
 ~~~~~~~~~~~~~~~~~~~~~~~~~