From cf614edd9802c3ac659cb7ed1e4a9590356f0bd5 Mon Sep 17 00:00:00 2001
From: "Jeffrey A. Clark" <aclark@aclark.net>
Date: Wed, 4 Jun 2025 17:13:31 -0400
Subject: [PATCH 01/20] Check for replica set or sharded cluster

---
 django_mongodb_backend/features.py | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index fa73461d9..8fa777c77 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -36,8 +36,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_temporal_subtraction = True
     # MongoDB stores datetimes in UTC.
     supports_timezones = False
-    # Not implemented: https://github.com/mongodb/django-mongodb-backend/issues/7
-    supports_transactions = False
     supports_unspecified_pk = True
     uses_savepoints = False
 
@@ -97,6 +95,22 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "expressions.tests.ExpressionOperatorTests.test_lefthand_transformed_field_bitwise_or",
     }
 
+    @cached_property
+    def supports_transactions(self):
+        """Confirm support for transactions."""
+        is_replica_set = False
+        is_sharded_cluster = False
+        with self.connection.cursor():
+            client = self.connection.connection
+            hello_response = client.admin.command("hello")
+            if "setName" in hello_response:
+                is_replica_set = True
+            if "msg" in client.admin.command("hello") and hello_response["msg"] == "isdbgrid":
+                is_sharded_cluster = True
+        if is_replica_set or is_sharded_cluster:
+            return True
+        return False
+
     @cached_property
     def django_test_expected_failures(self):
         expected_failures = super().django_test_expected_failures

From 392bc2fb1c1579b57fb34a94485d75bb97e7756b Mon Sep 17 00:00:00 2001
From: "Jeffrey A. Clark" <aclark@aclark.net>
Date: Fri, 6 Jun 2025 09:17:30 -0400
Subject: [PATCH 02/20] Check for wired tiger storage engine

---
 django_mongodb_backend/features.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index 8fa777c77..d358d7321 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -103,11 +103,17 @@ def supports_transactions(self):
         with self.connection.cursor():
             client = self.connection.connection
             hello_response = client.admin.command("hello")
+            server_status = client.admin.command("serverStatus")
             if "setName" in hello_response:
                 is_replica_set = True
-            if "msg" in client.admin.command("hello") and hello_response["msg"] == "isdbgrid":
+            if "msg" in hello_response and hello_response["msg"] == "isdbgrid":
                 is_sharded_cluster = True
-        if is_replica_set or is_sharded_cluster:
+            if (
+                "storageEngine" in server_status
+                and server_status["storageEngine"].get("name") == "wiredTiger"
+            ):
+                is_wired_tiger = True
+        if (is_replica_set or is_sharded_cluster) and is_wired_tiger:
             return True
         return False
 

From ca235e2e563c34f30f2e69424c26670812fb9d47 Mon Sep 17 00:00:00 2001
From: "Jeffrey A. Clark" <aclark@aclark.net>
Date: Fri, 6 Jun 2025 19:35:39 -0400
Subject: [PATCH 03/20] Add transaction support

---
 django_mongodb_backend/base.py     | 22 +++++++++++++++++++---
 django_mongodb_backend/compiler.py |  4 +++-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index c6110dbb7..6325e184a 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -139,6 +139,7 @@ def _isnull_operator(a, b):
     introspection_class = DatabaseIntrospection
     ops_class = DatabaseOperations
     validation_class = DatabaseValidation
+    session = None
 
     def get_collection(self, name, **kwargs):
         collection = Collection(self.database, name, **kwargs)
@@ -190,13 +191,28 @@ def _driver_info(self):
         return None
 
     def _commit(self):
-        pass
+        if self.session:
+            self.session.commit_transaction()
+            self.session.end_session()
+            self.session = None
 
     def _rollback(self):
         pass
 
-    def set_autocommit(self, autocommit, force_begin_transaction_with_broken_autocommit=False):
-        self.autocommit = autocommit
+    def _start_session(self):
+        if self.session is None:
+            self.session = self.connection.start_session()
+            self.session.start_transaction()
+
+    def _start_transaction_under_autocommit(self):
+        self._start_session()
+
+    def _set_autocommit(self, autocommit, force_begin_transaction_with_broken_autocommit=False):
+        if not autocommit:
+            self._start_session()
+        else:
+            if self.session:
+                self.commit()
 
     def _close(self):
         # Normally called by close(), this method is also called by some tests.
diff --git a/django_mongodb_backend/compiler.py b/django_mongodb_backend/compiler.py
index 12da13a1c..0176e6b74 100644
--- a/django_mongodb_backend/compiler.py
+++ b/django_mongodb_backend/compiler.py
@@ -685,7 +685,9 @@ def execute_sql(self, returning_fields=None):
     @wrap_database_errors
     def insert(self, docs, returning_fields=None):
         """Store a list of documents using field columns as element names."""
-        inserted_ids = self.collection.insert_many(docs).inserted_ids
+        inserted_ids = self.collection.insert_many(
+            docs, session=self.connection.session
+        ).inserted_ids
         return [(x,) for x in inserted_ids] if returning_fields else []
 
     @cached_property

From 001cc472ce2139fb2fc000335e8144253523475f Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Fri, 6 Jun 2025 21:31:46 -0400
Subject: [PATCH 04/20] pass session to queries

---
 django_mongodb_backend/base.py         |  7 +++----
 django_mongodb_backend/compiler.py     |  4 +++-
 django_mongodb_backend/features.py     | 12 ++----------
 django_mongodb_backend/query.py        |  8 ++++++--
 django_mongodb_backend/queryset.py     |  2 +-
 tests/raw_query_/test_raw_aggregate.py |  3 ++-
 6 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index 6325e184a..8f7b64932 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -197,7 +197,9 @@ def _commit(self):
             self.session = None
 
     def _rollback(self):
-        pass
+        if self.session:
+            self.session.abort_transaction()
+            self.session = None
 
     def _start_session(self):
         if self.session is None:
@@ -210,9 +212,6 @@ def _start_transaction_under_autocommit(self):
     def _set_autocommit(self, autocommit, force_begin_transaction_with_broken_autocommit=False):
         if not autocommit:
             self._start_session()
-        else:
-            if self.session:
-                self.commit()
 
     def _close(self):
         # Normally called by close(), this method is also called by some tests.
diff --git a/django_mongodb_backend/compiler.py b/django_mongodb_backend/compiler.py
index 0176e6b74..74a5d60e0 100644
--- a/django_mongodb_backend/compiler.py
+++ b/django_mongodb_backend/compiler.py
@@ -770,7 +770,9 @@ def execute_sql(self, result_type):
 
     @wrap_database_errors
     def update(self, criteria, pipeline):
-        return self.collection.update_many(criteria, pipeline).matched_count
+        return self.collection.update_many(
+            criteria, pipeline, session=self.connection.session
+        ).matched_count
 
     def check_query(self):
         super().check_query()
diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index d358d7321..14abf6c81 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -84,6 +84,8 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # Value.as_mql() doesn't call output_field.get_db_prep_save():
         # https://github.com/mongodb/django-mongodb-backend/issues/282
         "model_fields.test_jsonfield.TestSaveLoad.test_bulk_update_custom_get_prep_value",
+        # to debug
+        "transactions.tests.AtomicMiscTests.test_mark_for_rollback_on_error_in_transaction",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {
@@ -505,16 +507,6 @@ def django_test_expected_failures(self):
         "Connection health checks not implemented.": {
             "backends.base.test_base.ConnectionHealthChecksTests",
         },
-        "transaction.atomic() is not supported.": {
-            "backends.base.test_base.DatabaseWrapperLoggingTests",
-            "migrations.test_executor.ExecutorTests.test_atomic_operation_in_non_atomic_migration",
-            "migrations.test_operations.OperationTests.test_run_python_atomic",
-        },
-        "transaction.rollback() is not supported.": {
-            "transactions.tests.AtomicMiscTests.test_mark_for_rollback_on_error_in_autocommit",
-            "transactions.tests.AtomicMiscTests.test_mark_for_rollback_on_error_in_transaction",
-            "transactions.tests.NonAutocommitTests.test_orm_query_after_error_and_rollback",
-        },
         "migrate --fake-initial is not supported.": {
             "migrations.test_commands.MigrateTests.test_migrate_fake_initial",
             "migrations.test_commands.MigrateTests.test_migrate_fake_split_initial",
diff --git a/django_mongodb_backend/query.py b/django_mongodb_backend/query.py
index 049775205..8c18fcb03 100644
--- a/django_mongodb_backend/query.py
+++ b/django_mongodb_backend/query.py
@@ -63,7 +63,9 @@ def delete(self):
         """Execute a delete query."""
         if self.compiler.subqueries:
             raise NotSupportedError("Cannot use QuerySet.delete() when a subquery is required.")
-        return self.compiler.collection.delete_many(self.match_mql).deleted_count
+        return self.compiler.collection.delete_many(
+            self.match_mql, session=self.compiler.connection.session
+        ).deleted_count
 
     @wrap_database_errors
     def get_cursor(self):
@@ -71,7 +73,9 @@ def get_cursor(self):
         Return a pymongo CommandCursor that can be iterated on to give the
         results of the query.
         """
-        return self.compiler.collection.aggregate(self.get_pipeline())
+        return self.compiler.collection.aggregate(
+            self.get_pipeline(), session=self.compiler.connection.session
+        )
 
     def get_pipeline(self):
         pipeline = []
diff --git a/django_mongodb_backend/queryset.py b/django_mongodb_backend/queryset.py
index 4a2d884da..b02496fee 100644
--- a/django_mongodb_backend/queryset.py
+++ b/django_mongodb_backend/queryset.py
@@ -35,7 +35,7 @@ def __init__(self, pipeline, using, model):
     def _execute_query(self):
         connection = connections[self.using]
         collection = connection.get_collection(self.model._meta.db_table)
-        self.cursor = collection.aggregate(self.pipeline)
+        self.cursor = collection.aggregate(self.pipeline, session=connection.session)
 
     def __str__(self):
         return str(self.pipeline)
diff --git a/tests/raw_query_/test_raw_aggregate.py b/tests/raw_query_/test_raw_aggregate.py
index 72cd74d02..ce87311a6 100644
--- a/tests/raw_query_/test_raw_aggregate.py
+++ b/tests/raw_query_/test_raw_aggregate.py
@@ -182,7 +182,8 @@ def test_different_db_key_order(self):
             {
                 field.name: getattr(author, field.name)
                 for field in reversed(Author._meta.concrete_fields)
-            }
+            },
+            session=connection.session,
         )
         query = []
         authors = Author.objects.all()

From 04d3f2fb1856f69ea85486c0b902f6f889026b33 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Sat, 7 Jun 2025 08:30:04 -0400
Subject: [PATCH 05/20] disable transactions if not supported

---
 django_mongodb_backend/base.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index 8f7b64932..25b4a2d7e 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -191,12 +191,16 @@ def _driver_info(self):
         return None
 
     def _commit(self):
+        if not self.features.supports_transactions:
+            return
         if self.session:
             self.session.commit_transaction()
             self.session.end_session()
             self.session = None
 
     def _rollback(self):
+        if not self.features.supports_transactions:
+            return
         if self.session:
             self.session.abort_transaction()
             self.session = None
@@ -207,9 +211,13 @@ def _start_session(self):
             self.session.start_transaction()
 
     def _start_transaction_under_autocommit(self):
+        if not self.features.supports_transactions:
+            return
         self._start_session()
 
     def _set_autocommit(self, autocommit, force_begin_transaction_with_broken_autocommit=False):
+        if self.features.supports_transactions:
+            return
         if not autocommit:
             self._start_session()
 

From 176205ba17e53fe9df91b18ffe5cc81243cd20a7 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Sat, 7 Jun 2025 08:32:53 -0400
Subject: [PATCH 06/20] add replica set tests

---
 .github/workflows/test-python-replica.yml | 58 +++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 .github/workflows/test-python-replica.yml

diff --git a/.github/workflows/test-python-replica.yml b/.github/workflows/test-python-replica.yml
new file mode 100644
index 000000000..a51481bfd
--- /dev/null
+++ b/.github/workflows/test-python-replica.yml
@@ -0,0 +1,58 @@
+name: Python Tests on a replica test
+
+on:
+  pull_request:
+      paths:
+      - '**.py'
+      - '!setup.py'
+      - '.github/workflows/test-python-replica.yml'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+defaults:
+  run:
+    shell: bash -eux {0}
+
+jobs:
+  build:
+    name: Django Test Suite
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout django-mongodb-backend
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - name: install django-mongodb-backend
+        run: |
+          pip3 install --upgrade pip
+          pip3 install -e .
+      - name: Checkout Django
+        uses: actions/checkout@v4
+        with:
+          repository: 'mongodb-forks/django'
+          ref: 'mongodb-5.2.x'
+          path: 'django_repo'
+          persist-credentials: false
+      - name: Install system packages for Django's Python test dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install libmemcached-dev
+      - name: Install Django and its Python test dependencies
+        run: |
+          cd django_repo/tests/
+          pip3 install -e ..
+          pip3 install -r requirements/py3.txt
+      - name: Copy the test settings file
+        run: cp .github/workflows/mongodb_settings.py django_repo/tests/
+      - name: Copy the test runner file
+        run: cp .github/workflows/runtests.py django_repo/tests/runtests_.py
+      - name: Start MongoDB
+        uses: supercharge/mongodb-github-action@90004df786821b6308fb02299e5835d0dae05d0d # 1.12.0
+        with:
+          mongodb-version: 6.0
+          mongodb-replica-set: test-rs
+      - name: Run tests
+        run: python3 django_repo/tests/runtests.py --settings mongodb_settings -v 2

From b3b956f57e52a69e1a90351764864f57c894bd42 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Sat, 7 Jun 2025 09:03:33 -0400
Subject: [PATCH 07/20] skip union tests on transactions

---
 django_mongodb_backend/features.py | 5 +++++
 tests/queries_/test_objectid.py    | 4 +++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index 14abf6c81..3dcecc2e7 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -589,3 +589,8 @@ def supports_atlas_search(self):
             return False
         else:
             return True
+
+    @cached_property
+    def supports_select_union(self):
+        # Stage not supported inside of a multi-document transaction: $unionWith
+        return not self.supports_transactions
diff --git a/tests/queries_/test_objectid.py b/tests/queries_/test_objectid.py
index 490d1b334..36d9561a7 100644
--- a/tests/queries_/test_objectid.py
+++ b/tests/queries_/test_objectid.py
@@ -1,6 +1,6 @@
 from bson import ObjectId
 from django.core.exceptions import ValidationError
-from django.test import TestCase
+from django.test import TestCase, skipUnlessDBFeature
 
 from .models import Order, OrderItem, Tag
 
@@ -75,6 +75,7 @@ def test_filter_parent_by_children_values_obj(self):
         parent_qs = Tag.objects.filter(children__id__in=child_ids).distinct().order_by("name")
         self.assertSequenceEqual(parent_qs, [self.t1])
 
+    @skipUnlessDBFeature("supports_select_union")
     def test_filter_group_id_union_with_str(self):
         """Combine queries using union with string values."""
         qs_a = Tag.objects.filter(group_id=self.group_id_str_1)
@@ -82,6 +83,7 @@ def test_filter_group_id_union_with_str(self):
         union_qs = qs_a.union(qs_b).order_by("name")
         self.assertSequenceEqual(union_qs, [self.t3, self.t4])
 
+    @skipUnlessDBFeature("supports_select_union")
     def test_filter_group_id_union_with_obj(self):
         """Combine queries using union with ObjectId values."""
         qs_a = Tag.objects.filter(group_id=self.group_id_obj_1)

From 8087a7c6177a9d98bb47e77fbe6321584fa8c44d Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Sat, 7 Jun 2025 10:18:07 -0400
Subject: [PATCH 08/20] add transaction logging

---
 django_mongodb_backend/base.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index 25b4a2d7e..fff19330e 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -3,6 +3,7 @@
 
 from django.core.exceptions import ImproperlyConfigured
 from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.utils import debug_transaction
 from django.utils.asyncio import async_unsafe
 from django.utils.functional import cached_property
 from pymongo.collection import Collection
@@ -194,7 +195,8 @@ def _commit(self):
         if not self.features.supports_transactions:
             return
         if self.session:
-            self.session.commit_transaction()
+            with debug_transaction(self, "session.commit_transaction()"):
+                self.session.commit_transaction()
             self.session.end_session()
             self.session = None
 
@@ -202,13 +204,15 @@ def _rollback(self):
         if not self.features.supports_transactions:
             return
         if self.session:
-            self.session.abort_transaction()
+            with debug_transaction(self, "session.abort_transaction()"):
+                self.session.abort_transaction()
             self.session = None
 
     def _start_session(self):
         if self.session is None:
             self.session = self.connection.start_session()
-            self.session.start_transaction()
+            with debug_transaction(self, "session.start_transaction()"):
+                self.session.start_transaction()
 
     def _start_transaction_under_autocommit(self):
         if not self.features.supports_transactions:

From c9b639aa607dcfcf5f92da31d0438083c044de6f Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Sat, 7 Jun 2025 11:02:38 -0400
Subject: [PATCH 09/20] add skips for composite_pk tests

---
 django_mongodb_backend/features.py | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index 3dcecc2e7..c60c32719 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -545,8 +545,18 @@ def django_test_expected_failures(self):
             "foreign_object.test_tuple_lookups.TupleLookupsTests",
         },
         "ColPairs is not supported.": {
-            # 'ColPairs' object has no attribute 'as_mql'
             "auth_tests.test_views.CustomUserCompositePrimaryKeyPasswordResetTest",
+            "composite_pk.test_aggregate.CompositePKAggregateTests",
+            "composite_pk.test_create.CompositePKCreateTests",
+            "composite_pk.test_delete.CompositePKDeleteTests",
+            "composite_pk.test_filter.CompositePKFilterTests",
+            "composite_pk.test_get.CompositePKGetTests",
+            "composite_pk.test_models.CompositePKModelsTests",
+            "composite_pk.test_order_by.CompositePKOrderByTests",
+            "composite_pk.test_update.CompositePKUpdateTests",
+            "composite_pk.test_values.CompositePKValuesTests",
+            "composite_pk.tests.CompositePKTests",
+            "composite_pk.tests.CompositePKFixturesTests",
         },
         "Custom lookups are not supported.": {
             "custom_lookups.tests.BilateralTransformTests",

From 939159905d06a04538a1792c0884bc6c50751c8c Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Sat, 7 Jun 2025 20:36:44 -0400
Subject: [PATCH 10/20] fix backend_ tests

---
 tests/backend_/test_base.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tests/backend_/test_base.py b/tests/backend_/test_base.py
index 7695b6f4d..9d4e7006f 100644
--- a/tests/backend_/test_base.py
+++ b/tests/backend_/test_base.py
@@ -1,7 +1,7 @@
 from django.core.exceptions import ImproperlyConfigured
 from django.db import connection
 from django.db.backends.signals import connection_created
-from django.test import SimpleTestCase, TestCase
+from django.test import SimpleTestCase, TransactionTestCase
 
 from django_mongodb_backend.base import DatabaseWrapper
 
@@ -15,7 +15,9 @@ def test_database_name_empty(self):
             DatabaseWrapper(settings).get_connection_params()
 
 
-class DatabaseWrapperConnectionTests(TestCase):
+class DatabaseWrapperConnectionTests(TransactionTestCase):
+    available_apps = ["backend_"]
+
     def test_set_autocommit(self):
         self.assertIs(connection.get_autocommit(), True)
         connection.set_autocommit(False)

From 4eb66e99fc70645596a22517f4102579935c61db Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Sat, 7 Jun 2025 20:37:44 -0400
Subject: [PATCH 11/20] add expected transaction failures

---
 django_mongodb_backend/features.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index c60c32719..0c9e5719d 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -96,6 +96,11 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "expressions.tests.ExpressionOperatorTests.test_lefthand_bitwise_xor_right_null",
         "expressions.tests.ExpressionOperatorTests.test_lefthand_transformed_field_bitwise_or",
     }
+    _django_test_expected_failures_transactions = {
+        # When get_or_create() fails with IntegrityError, the transaction is no longer usable.
+        "get_or_create.tests.UpdateOrCreateTests.test_manual_primary_key_test",
+        "get_or_create.tests.UpdateOrCreateTestsWithManualPKs.test_create_with_duplicate_primary_key",
+    }
 
     @cached_property
     def supports_transactions(self):
@@ -125,6 +130,8 @@ def django_test_expected_failures(self):
         expected_failures.update(self._django_test_expected_failures)
         if not self.is_mongodb_6_3:
             expected_failures.update(self._django_test_expected_failures_bitwise)
+        if self.supports_transactions:
+            expected_failures.update(self._django_test_expected_failures_transactions)
         return expected_failures
 
     django_test_skips = {

From 749ab890e5e39e65d1a935cecee4469a63e9fd2c Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Mon, 9 Jun 2025 08:32:18 -0400
Subject: [PATCH 12/20] move session to instance variable; clear commit hooks
 in close_pool()

---
 django_mongodb_backend/base.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index fff19330e..7f66ab1d0 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -2,6 +2,7 @@
 import os
 
 from django.core.exceptions import ImproperlyConfigured
+from django.db import DEFAULT_DB_ALIAS
 from django.db.backends.base.base import BaseDatabaseWrapper
 from django.db.backends.utils import debug_transaction
 from django.utils.asyncio import async_unsafe
@@ -140,7 +141,10 @@ def _isnull_operator(a, b):
     introspection_class = DatabaseIntrospection
     ops_class = DatabaseOperations
     validation_class = DatabaseValidation
-    session = None
+
+    def __init__(self, settings_dict, alias=DEFAULT_DB_ALIAS):
+        super().__init__(settings_dict, alias=alias)
+        self.session = None
 
     def get_collection(self, name, **kwargs):
         collection = Collection(self.database, name, **kwargs)
@@ -237,6 +241,9 @@ def close(self):
 
     def close_pool(self):
         """Close the MongoClient."""
+        # Clear commit hooks and session.
+        self.run_on_commit = []
+        self.session = None
         connection = self.connection
         if connection is None:
             return

From f26e114b8061571f1a6792a73b679ac43fbcb78c Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Mon, 9 Jun 2025 08:34:25 -0400
Subject: [PATCH 13/20] remove redundant test script

Transactions are tested in Atlas tests.
---
 .github/workflows/test-python-atlas.yml   |  2 +-
 .github/workflows/test-python-replica.yml | 58 -----------------------
 2 files changed, 1 insertion(+), 59 deletions(-)
 delete mode 100644 .github/workflows/test-python-replica.yml

diff --git a/.github/workflows/test-python-atlas.yml b/.github/workflows/test-python-atlas.yml
index 175dfe183..f84a99345 100644
--- a/.github/workflows/test-python-atlas.yml
+++ b/.github/workflows/test-python-atlas.yml
@@ -53,4 +53,4 @@ jobs:
         working-directory: .
         run: bash .github/workflows/start_local_atlas.sh mongodb/mongodb-atlas-local:7
       - name: Run tests
-        run: python3 django_repo/tests/runtests_.py
+        run: python3 django_repo/tests/runtests.py --settings mongodb_settings -v 2
diff --git a/.github/workflows/test-python-replica.yml b/.github/workflows/test-python-replica.yml
deleted file mode 100644
index a51481bfd..000000000
--- a/.github/workflows/test-python-replica.yml
+++ /dev/null
@@ -1,58 +0,0 @@
-name: Python Tests on a replica test
-
-on:
-  pull_request:
-      paths:
-      - '**.py'
-      - '!setup.py'
-      - '.github/workflows/test-python-replica.yml'
-  workflow_dispatch:
-
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
-
-defaults:
-  run:
-    shell: bash -eux {0}
-
-jobs:
-  build:
-    name: Django Test Suite
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout django-mongodb-backend
-        uses: actions/checkout@v4
-        with:
-          persist-credentials: false
-      - name: install django-mongodb-backend
-        run: |
-          pip3 install --upgrade pip
-          pip3 install -e .
-      - name: Checkout Django
-        uses: actions/checkout@v4
-        with:
-          repository: 'mongodb-forks/django'
-          ref: 'mongodb-5.2.x'
-          path: 'django_repo'
-          persist-credentials: false
-      - name: Install system packages for Django's Python test dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install libmemcached-dev
-      - name: Install Django and its Python test dependencies
-        run: |
-          cd django_repo/tests/
-          pip3 install -e ..
-          pip3 install -r requirements/py3.txt
-      - name: Copy the test settings file
-        run: cp .github/workflows/mongodb_settings.py django_repo/tests/
-      - name: Copy the test runner file
-        run: cp .github/workflows/runtests.py django_repo/tests/runtests_.py
-      - name: Start MongoDB
-        uses: supercharge/mongodb-github-action@90004df786821b6308fb02299e5835d0dae05d0d # 1.12.0
-        with:
-          mongodb-version: 6.0
-          mongodb-replica-set: test-rs
-      - name: Run tests
-        run: python3 django_repo/tests/runtests.py --settings mongodb_settings -v 2

From 57c3683412cec4611679980265a2f331c42f9ed5 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Mon, 9 Jun 2025 10:29:25 -0400
Subject: [PATCH 14/20] add tests for DatabaseFeatures.supports_transactions

---
 django_mongodb_backend/features.py | 39 +++++++--------
 tests/backend_/test_features.py    | 76 ++++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+), 22 deletions(-)
 create mode 100644 tests/backend_/test_features.py

diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index 0c9e5719d..8ccf0ac83 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -102,28 +102,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "get_or_create.tests.UpdateOrCreateTestsWithManualPKs.test_create_with_duplicate_primary_key",
     }
 
-    @cached_property
-    def supports_transactions(self):
-        """Confirm support for transactions."""
-        is_replica_set = False
-        is_sharded_cluster = False
-        with self.connection.cursor():
-            client = self.connection.connection
-            hello_response = client.admin.command("hello")
-            server_status = client.admin.command("serverStatus")
-            if "setName" in hello_response:
-                is_replica_set = True
-            if "msg" in hello_response and hello_response["msg"] == "isdbgrid":
-                is_sharded_cluster = True
-            if (
-                "storageEngine" in server_status
-                and server_status["storageEngine"].get("name") == "wiredTiger"
-            ):
-                is_wired_tiger = True
-        if (is_replica_set or is_sharded_cluster) and is_wired_tiger:
-            return True
-        return False
-
     @cached_property
     def django_test_expected_failures(self):
         expected_failures = super().django_test_expected_failures
@@ -611,3 +589,20 @@ def supports_atlas_search(self):
     def supports_select_union(self):
         # Stage not supported inside of a multi-document transaction: $unionWith
         return not self.supports_transactions
+
+    @cached_property
+    def supports_transactions(self):
+        """
+        Transactions are enabled if the MongoDB configuration supports it:
+        MongoDB must be configured as a replica set or sharded cluster, and
+        the store engine must be WiredTiger.
+        """
+        self.connection.ensure_connection()
+        client = self.connection.connection.admin
+        hello_response = client.command("hello")
+        is_replica_set = "setName" in hello_response
+        is_sharded_cluster = hello_response.get("msg") == "isdbgrid"
+        if is_replica_set or is_sharded_cluster:
+            engine = client.command("serverStatus").get("storageEngine", {})
+            return engine.get("name") == "wiredTiger"
+        return False
diff --git a/tests/backend_/test_features.py b/tests/backend_/test_features.py
new file mode 100644
index 000000000..3b18e64ae
--- /dev/null
+++ b/tests/backend_/test_features.py
@@ -0,0 +1,76 @@
+from unittest.mock import patch
+
+from django.db import connection
+from django.test import TestCase
+
+
+class SupportsTransactionsTests(TestCase):
+    def setUp(self):
+        # Clear the cached property.
+        del connection.features.supports_transactions
+
+    def tearDown(self):
+        del connection.features.supports_transactions
+
+    def test_replica_set(self):
+        """A replica set supports transactions."""
+
+        def mocked_command(command):
+            if command == "hello":
+                return {"setName": "foo"}
+            if command == "serverStatus":
+                return {"storageEngine": {"name": "wiredTiger"}}
+            raise Exception("Unexpected command")
+
+        with patch("pymongo.synchronous.database.Database.command", wraps=mocked_command):
+            self.assertIs(connection.features.supports_transactions, True)
+
+    def test_replica_set_other_storage_engine(self):
+        """No support on a non-wiredTiger replica set."""
+
+        def mocked_command(command):
+            if command == "hello":
+                return {"setName": "foo"}
+            if command == "serverStatus":
+                return {"storageEngine": {"name": "other"}}
+            raise Exception("Unexpected command")
+
+        with patch("pymongo.synchronous.database.Database.command", wraps=mocked_command):
+            self.assertIs(connection.features.supports_transactions, False)
+
+    def test_sharded_cluster(self):
+        """A sharded cluster with wiredTiger storage engine supports them."""
+
+        def mocked_command(command):
+            if command == "hello":
+                return {"msg": "isdbgrid"}
+            if command == "serverStatus":
+                return {"storageEngine": {"name": "wiredTiger"}}
+            raise Exception("Unexpected command")
+
+        with patch("pymongo.synchronous.database.Database.command", wraps=mocked_command):
+            self.assertIs(connection.features.supports_transactions, True)
+
+    def test_sharded_cluster_other_storage_engine(self):
+        """No support on a non-wiredTiger shared cluster."""
+
+        def mocked_command(command):
+            if command == "hello":
+                return {"msg": "isdbgrid"}
+            if command == "serverStatus":
+                return {"storageEngine": {"name": "other"}}
+            raise Exception("Unexpected command")
+
+        with patch("pymongo.synchronous.database.Database.command", wraps=mocked_command):
+            self.assertIs(connection.features.supports_transactions, False)
+
+    def test_no_support(self):
+        """No support on a non-replica set, non-sharded cluster."""
+
+        def mocked_command(command):
+            if command == "hello":
+                return {}
+            raise Exception("Unexpected command")
+
+        with patch("pymongo.synchronous.database.Database.command", wraps=mocked_command):
+            self.assertIs(connection.features.supports_transactions, False)

From 65258b34146f10456d44a8e8805e3f9846dd3729 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Mon, 9 Jun 2025 10:48:50 -0400
Subject: [PATCH 15/20] docs

---
 django_mongodb_backend/features.py  |  3 ++-
 docs/source/conf.py                 |  1 +
 docs/source/ref/database.rst        | 42 +++++++++++++++++++++++++++++
 docs/source/releases/5.2.x.rst      | 10 +++++++
 docs/source/topics/known-issues.rst |  6 +----
 5 files changed, 56 insertions(+), 6 deletions(-)

diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index 8ccf0ac83..eb75d4ae6 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -97,7 +97,8 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "expressions.tests.ExpressionOperatorTests.test_lefthand_transformed_field_bitwise_or",
     }
     _django_test_expected_failures_transactions = {
-        # When get_or_create() fails with IntegrityError, the transaction is no longer usable.
+        # When update_or_create() fails with IntegrityError, the transaction
+        # is no longer usable.
         "get_or_create.tests.UpdateOrCreateTests.test_manual_primary_key_test",
         "get_or_create.tests.UpdateOrCreateTestsWithManualPKs.test_create_with_duplicate_primary_key",
     }
diff --git a/docs/source/conf.py b/docs/source/conf.py
index a4e549381..2f1c8675a 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -45,6 +45,7 @@
     "pymongo": ("https://pymongo.readthedocs.io/en/stable/", None),
     "python": ("https://docs.python.org/3/", None),
     "atlas": ("https://www.mongodb.com/docs/atlas/", None),
+    "manual": ("https://www.mongodb.com/docs/manual/", None),
 }
 
 root_doc = "contents"
diff --git a/docs/source/ref/database.rst b/docs/source/ref/database.rst
index 365e1c73d..3b0d0930c 100644
--- a/docs/source/ref/database.rst
+++ b/docs/source/ref/database.rst
@@ -41,3 +41,45 @@ effect. Rather, if you need to close the connection pool, use
 .. versionadded:: 5.2.0b0
 
     Support for connection pooling and ``connection.close_pool()`` were added.
+
+.. _transactions:
+
+Transactions
+============
+
+.. versionadded:: 5.2.0b2
+
+Support for :doc:`Django's transactions APIs <django:topics/db/transactions>`
+is enabled if the MongoDB configuration supports them: MongoDB must be
+configured as a :doc:`replica set <manual:replication>` or :doc:`sharded
+cluster <manual:sharding>`, and the store engine must be :doc:`WiredTiger
+<manual:core/wiredtiger>`.
+
+If transactions aren't supported, query execution uses Django and MongoDB's
+default behavior of autocommit mode. Each query is immediately committed to the
+database. Django's transaction management APIs, such as
+:func:`~django.db.transaction.atomic`, function as no-ops.
+
+.. _transactions-limitations:
+
+Limitations
+-----------
+
+MongoDB's transaction limitations that are applicable to Django are:
+
+- :meth:`QuerySet.union() <django.db.models.query.QuerySet.union>` is not
+  supported inside a transaction.
+- If a transaction raises an exception, the transaction is no longer usable.
+  For example, if the update stage of :meth:`QuerySet.update_or_create()
+  <django.db.models.query.QuerySet.update_or_create>` fails with
+  :class:`~django.db.IntegrityError` due to a unique constraint violation, the
+  create stage won't be able to proceed.
+  :class:`pymongo.errors.OperationFailure` is raised, wrapped by
+  :class:`django.db.DatabaseError`.
+- Savepoints (i.e. nested :func:`~django.db.transaction.atomic` blocks) aren't
+  supported. The outermost :func:`~django.db.transaction.atomic` will start
+  a transaction while any subsequent :func:`~django.db.transaction.atomic`
+  blocks will have no effect.
+- Migration operations aren't :ref:`wrapped in a transaction
+  <topics/migrations:transactions>` because of MongoDB restrictions such as
+  adding indexes to existing collections while in a transaction.
diff --git a/docs/source/releases/5.2.x.rst b/docs/source/releases/5.2.x.rst
index de4b6efcb..e5e9b05ff 100644
--- a/docs/source/releases/5.2.x.rst
+++ b/docs/source/releases/5.2.x.rst
@@ -2,6 +2,16 @@
 Django MongoDB Backend 5.2.x
 ============================
 
+5.2.0 beta 2
+============
+
+*Unreleased*
+
+New features
+------------
+
+- Added support for :ref:`database transactions <transactions>`.
+
 5.2.0 beta 1
 ============
 
diff --git a/docs/source/topics/known-issues.rst b/docs/source/topics/known-issues.rst
index 4b9edee70..60628f816 100644
--- a/docs/source/topics/known-issues.rst
+++ b/docs/source/topics/known-issues.rst
@@ -80,11 +80,7 @@ Database functions
 Transaction management
 ======================
 
-Query execution uses Django and MongoDB's default behavior of autocommit mode.
-Each query is immediately committed to the database.
-
-Django's :doc:`transaction management APIs <django:topics/db/transactions>`
-are not supported.
+See :ref:`transactions` for details.
 
 Database introspection
 ======================

From 6b86a8b29123b69bef7cf1b99663e46e1a52834e Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Tue, 10 Jun 2025 08:15:22 -0400
Subject: [PATCH 16/20] add validation of broken transactions

---
 django_mongodb_backend/base.py     |  4 ++++
 django_mongodb_backend/compiler.py |  2 ++
 django_mongodb_backend/features.py | 30 ++++++++++++++++++++++++++----
 django_mongodb_backend/query.py    |  2 ++
 4 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index 7f66ab1d0..dcc492863 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -259,6 +259,10 @@ def close_pool(self):
     def cursor(self):
         return Cursor()
 
+    def validate_no_broken_transaction(self):
+        if self.features.supports_transactions:
+            super().validate_no_broken_transaction()
+
     def get_database_version(self):
         """Return a tuple of the database's version."""
         return tuple(self.connection.server_info()["versionArray"])
diff --git a/django_mongodb_backend/compiler.py b/django_mongodb_backend/compiler.py
index 74a5d60e0..b7e264f8b 100644
--- a/django_mongodb_backend/compiler.py
+++ b/django_mongodb_backend/compiler.py
@@ -685,6 +685,7 @@ def execute_sql(self, returning_fields=None):
     @wrap_database_errors
     def insert(self, docs, returning_fields=None):
         """Store a list of documents using field columns as element names."""
+        self.connection.validate_no_broken_transaction()
         inserted_ids = self.collection.insert_many(
             docs, session=self.connection.session
         ).inserted_ids
@@ -770,6 +771,7 @@ def execute_sql(self, result_type):
 
     @wrap_database_errors
     def update(self, criteria, pipeline):
+        self.connection.validate_no_broken_transaction()
         return self.collection.update_many(
             criteria, pipeline, session=self.connection.session
         ).matched_count
diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index eb75d4ae6..92697bde1 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -48,8 +48,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "aggregation.tests.AggregateTestCase.test_order_by_aggregate_transform",
         # 'NulledTransform' object has no attribute 'as_mql'.
         "lookup.tests.LookupTests.test_exact_none_transform",
-        # "Save with update_fields did not affect any rows."
-        "basic.tests.SelectOnSaveTests.test_select_on_save_lying_update",
         # BaseExpression.convert_value() crashes with Decimal128.
         "aggregation.tests.AggregateTestCase.test_combine_different_types",
         "annotations.tests.NonAggregateAnnotationTestCase.test_combined_f_expression_annotation_with_aggregation",
@@ -84,8 +82,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # Value.as_mql() doesn't call output_field.get_db_prep_save():
         # https://github.com/mongodb/django-mongodb-backend/issues/282
         "model_fields.test_jsonfield.TestSaveLoad.test_bulk_update_custom_get_prep_value",
-        # to debug
-        "transactions.tests.AtomicMiscTests.test_mark_for_rollback_on_error_in_transaction",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {
@@ -96,11 +92,35 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "expressions.tests.ExpressionOperatorTests.test_lefthand_bitwise_xor_right_null",
         "expressions.tests.ExpressionOperatorTests.test_lefthand_transformed_field_bitwise_or",
     }
+    _django_test_expected_failures_no_transactions = {
+        # "Save with update_fields did not affect any rows." instead of
+        # "An error occurred in the current transaction. You can't execute
+        # queries until the end of the 'atomic' block."
+        "basic.tests.SelectOnSaveTests.test_select_on_save_lying_update",
+    }
     _django_test_expected_failures_transactions = {
         # When update_or_create() fails with IntegrityError, the transaction
         # is no longer usable.
         "get_or_create.tests.UpdateOrCreateTests.test_manual_primary_key_test",
         "get_or_create.tests.UpdateOrCreateTestsWithManualPKs.test_create_with_duplicate_primary_key",
+        # Tests that require savepoints
+        "admin_views.tests.AdminViewBasicTest.test_disallowed_to_field",
+        "admin_views.tests.AdminViewPermissionsTest.test_add_view",
+        "admin_views.tests.AdminViewPermissionsTest.test_change_view",
+        "admin_views.tests.AdminViewPermissionsTest.test_change_view_save_as_new",
+        "admin_views.tests.AdminViewPermissionsTest.test_delete_view",
+        "auth_tests.test_views.ChangelistTests.test_view_user_password_is_readonly",
+        "fixtures.tests.FixtureLoadingTests.test_loaddata_app_option",
+        "fixtures.tests.FixtureLoadingTests.test_unmatched_identifier_loading",
+        "fixtures_model_package.tests.FixtureTestCase.test_loaddata",
+        "get_or_create.tests.GetOrCreateTests.test_get_or_create_invalid_params",
+        "get_or_create.tests.UpdateOrCreateTests.test_integrity",
+        "many_to_many.tests.ManyToManyTests.test_add",
+        "many_to_one.tests.ManyToOneTests.test_fk_assignment_and_related_object_cache",
+        "model_fields.test_booleanfield.BooleanFieldTests.test_null_default",
+        "model_fields.test_floatfield.TestFloatField.test_float_validates_object",
+        "multiple_database.tests.QueryTestCase.test_generic_key_cross_database_protection",
+        "multiple_database.tests.QueryTestCase.test_m2m_cross_database_protection",
     }
 
     @cached_property
@@ -111,6 +131,8 @@ def django_test_expected_failures(self):
             expected_failures.update(self._django_test_expected_failures_bitwise)
         if self.supports_transactions:
             expected_failures.update(self._django_test_expected_failures_transactions)
+        else:
+            expected_failures.update(self._django_test_expected_failures_no_transactions)
         return expected_failures
 
     django_test_skips = {
diff --git a/django_mongodb_backend/query.py b/django_mongodb_backend/query.py
index 8c18fcb03..d59bc1631 100644
--- a/django_mongodb_backend/query.py
+++ b/django_mongodb_backend/query.py
@@ -61,6 +61,7 @@ def __repr__(self):
     @wrap_database_errors
     def delete(self):
         """Execute a delete query."""
+        self.compiler.connection.validate_no_broken_transaction()
         if self.compiler.subqueries:
             raise NotSupportedError("Cannot use QuerySet.delete() when a subquery is required.")
         return self.compiler.collection.delete_many(
@@ -73,6 +74,7 @@ def get_cursor(self):
         Return a pymongo CommandCursor that can be iterated on to give the
         results of the query.
         """
+        self.compiler.connection.validate_no_broken_transaction()
         return self.compiler.collection.aggregate(
             self.get_pipeline(), session=self.compiler.connection.session
         )

From 6eba5a446ca3fe33ee6ece6325bd2dbf2b0aee45 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Mon, 16 Jun 2025 13:59:21 -0400
Subject: [PATCH 17/20] rename _start_session()

---
 django_mongodb_backend/base.py | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index dcc492863..65bfca9b9 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -212,22 +212,30 @@ def _rollback(self):
                 self.session.abort_transaction()
             self.session = None
 
-    def _start_session(self):
+    def _start_transaction(self):
         if self.session is None:
             self.session = self.connection.start_session()
             with debug_transaction(self, "session.start_transaction()"):
                 self.session.start_transaction()
 
     def _start_transaction_under_autocommit(self):
+        # Implementing this hook (intended only for SQLite), allows
+        # BaseDatabaseWrapper.set_autocommit() to use it to start a transaction
+        # rather than set_autocommit(), bypassing set_autocommit()'s call to
+        # debug_transaction(self, "BEGIN") which isn't semantic for a no-SQL
+        # backend.
         if not self.features.supports_transactions:
             return
-        self._start_session()
+        self._start_transaction()
 
     def _set_autocommit(self, autocommit, force_begin_transaction_with_broken_autocommit=False):
         if self.features.supports_transactions:
             return
+        # Besides @transaction.atomic() (which uses
+        # _start_transaction_under_autocommit(), disabling autocommit is
+        # another way to start a transaction.
         if not autocommit:
-            self._start_session()
+            self._start_transaction()
 
     def _close(self):
         # Normally called by close(), this method is also called by some tests.

From 5b3b757b45333965d883e7088ff587c3b5964621 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Mon, 16 Jun 2025 16:58:30 -0400
Subject: [PATCH 18/20] add @requires_transaction_support

---
 django_mongodb_backend/base.py | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index 65bfca9b9..1c35fce27 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -34,6 +34,17 @@ def __exit__(self, exception_type, exception_value, exception_traceback):
         pass
 
 
+def requires_transaction_support(func):
+    """Make a method a no-op if transactions aren't supported."""
+
+    def wrapper(self, *args, **kwargs):
+        if not self.features.supports_transactions:
+            return
+        func(self, *args, **kwargs)
+
+    return wrapper
+
+
 class DatabaseWrapper(BaseDatabaseWrapper):
     data_types = {
         "AutoField": "int",
@@ -195,18 +206,16 @@ def _driver_info(self):
             return DriverInfo("django-mongodb-backend", django_mongodb_backend_version)
         return None
 
+    @requires_transaction_support
     def _commit(self):
-        if not self.features.supports_transactions:
-            return
         if self.session:
             with debug_transaction(self, "session.commit_transaction()"):
                 self.session.commit_transaction()
             self.session.end_session()
             self.session = None
 
+    @requires_transaction_support
     def _rollback(self):
-        if not self.features.supports_transactions:
-            return
         if self.session:
             with debug_transaction(self, "session.abort_transaction()"):
                 self.session.abort_transaction()
@@ -218,19 +227,17 @@ def _start_transaction(self):
             with debug_transaction(self, "session.start_transaction()"):
                 self.session.start_transaction()
 
+    @requires_transaction_support
     def _start_transaction_under_autocommit(self):
         # Implementing this hook (intended only for SQLite), allows
         # BaseDatabaseWrapper.set_autocommit() to use it to start a transaction
         # rather than set_autocommit(), bypassing set_autocommit()'s call to
         # debug_transaction(self, "BEGIN") which isn't semantic for a no-SQL
         # backend.
-        if not self.features.supports_transactions:
-            return
         self._start_transaction()
 
+    @requires_transaction_support
     def _set_autocommit(self, autocommit, force_begin_transaction_with_broken_autocommit=False):
-        if self.features.supports_transactions:
-            return
         # Besides @transaction.atomic() (which uses
         # _start_transaction_under_autocommit(), disabling autocommit is
         # another way to start a transaction.
@@ -267,9 +274,9 @@ def close_pool(self):
     def cursor(self):
         return Cursor()
 
+    @requires_transaction_support
     def validate_no_broken_transaction(self):
-        if self.features.supports_transactions:
-            super().validate_no_broken_transaction()
+        super().validate_no_broken_transaction()
 
     def get_database_version(self):
         """Return a tuple of the database's version."""

From 2ffbaeb1b5010dca0c053356713ab0c2fc84e07f Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Mon, 16 Jun 2025 18:34:13 -0400
Subject: [PATCH 19/20] always end session

---
 django_mongodb_backend/base.py | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/django_mongodb_backend/base.py b/django_mongodb_backend/base.py
index 1c35fce27..fc21fa5b6 100644
--- a/django_mongodb_backend/base.py
+++ b/django_mongodb_backend/base.py
@@ -211,22 +211,27 @@ def _commit(self):
         if self.session:
             with debug_transaction(self, "session.commit_transaction()"):
                 self.session.commit_transaction()
-            self.session.end_session()
-            self.session = None
+            self._end_session()
 
     @requires_transaction_support
     def _rollback(self):
         if self.session:
             with debug_transaction(self, "session.abort_transaction()"):
                 self.session.abort_transaction()
-            self.session = None
+            self._end_session()
 
     def _start_transaction(self):
+        # Private API, specific to this backend.
         if self.session is None:
             self.session = self.connection.start_session()
             with debug_transaction(self, "session.start_transaction()"):
                 self.session.start_transaction()
 
+    def _end_session(self):
+        # Private API, specific to this backend.
+        self.session.end_session()
+        self.session = None
+
     @requires_transaction_support
     def _start_transaction_under_autocommit(self):
         # Implementing this hook (intended only for SQLite), allows
@@ -258,7 +263,8 @@ def close_pool(self):
         """Close the MongoClient."""
         # Clear commit hooks and session.
         self.run_on_commit = []
-        self.session = None
+        if self.session:
+            self._end_session()
         connection = self.connection
         if connection is None:
             return

From d0a88a190f9b6c998eb6cd5314916c8b1f59fd67 Mon Sep 17 00:00:00 2001
From: "Jeffrey A. Clark" <aclark@aclark.net>
Date: Tue, 17 Jun 2025 10:44:16 -0400
Subject: [PATCH 20/20] Add queryable encryption config

---
 django_mongodb_backend/__init__.py     |  4 +-
 django_mongodb_backend/features.py     | 10 +++++
 django_mongodb_backend/utils.py        | 60 ++++++++++++++++++++++++++
 tests/backend_/utils/test_parse_uri.py | 10 ++++-
 4 files changed, 81 insertions(+), 3 deletions(-)

diff --git a/django_mongodb_backend/__init__.py b/django_mongodb_backend/__init__.py
index 00700421a..1c9f88f39 100644
--- a/django_mongodb_backend/__init__.py
+++ b/django_mongodb_backend/__init__.py
@@ -2,7 +2,7 @@
 
 # Check Django compatibility before other imports which may fail if the
 # wrong version of Django is installed.
-from .utils import check_django_compatability, parse_uri
+from .utils import check_django_compatability, get_auto_encryption_options, parse_uri
 
 check_django_compatability()
 
@@ -15,7 +15,7 @@
 from .lookups import register_lookups  # noqa: E402
 from .query import register_nodes  # noqa: E402
 
-__all__ = ["parse_uri"]
+__all__ = ["get_auto_encryption_options", "parse_uri"]
 
 register_aggregates()
 register_checks()
diff --git a/django_mongodb_backend/features.py b/django_mongodb_backend/features.py
index 92697bde1..487abffec 100644
--- a/django_mongodb_backend/features.py
+++ b/django_mongodb_backend/features.py
@@ -629,3 +629,13 @@ def supports_transactions(self):
             engine = client.command("serverStatus").get("storageEngine", {})
             return engine.get("name") == "wiredTiger"
         return False
+
+    @cached_property
+    def supports_queryable_encryption(self):
+        """
+        Queryable Encryption is available if the server is Atlas or Enterprise.
+        """
+        self.connection.ensure_connection()
+        client = self.connection.connection.admin
+        build_info = client.command("buildInfo")
+        return "enterprise" in build_info.get("modules")
diff --git a/django_mongodb_backend/utils.py b/django_mongodb_backend/utils.py
index ced60bc8e..15ebc1032 100644
--- a/django_mongodb_backend/utils.py
+++ b/django_mongodb_backend/utils.py
@@ -1,5 +1,8 @@
 import copy
+import os
 import time
+from pathlib import Path
+from urllib.parse import urlencode
 
 import django
 from django.conf import settings
@@ -8,6 +11,7 @@
 from django.utils.functional import SimpleLazyObject
 from django.utils.text import format_lazy
 from django.utils.version import get_version_tuple
+from pymongo.encryption_options import AutoEncryptionOpts
 from pymongo.uri_parser import parse_uri as pymongo_parse_uri
 
 
@@ -28,6 +32,62 @@ def check_django_compatability():
         )
 
 
+# Queryable Encryption-related functions based on helpers from Python Queryable
+# Encryption Tutorial
+# https://github.com/mongodb/docs/tree/master/source/includes/qe-tutorials/python/
+def _get_kms_provider_credentials(kms_provider_name):
+    """
+    "A KMS is a remote service that securely stores and manages your encryption keys."
+
+    Via https://www.mongodb.com/docs/manual/core/queryable-encryption/quick-start/
+
+    Here we check the provider name and return the appropriate credentials.
+    """
+    # TODO: Add support for other KMS providers.
+    if kms_provider_name == "local":
+        if not Path("./customer-master-key.txt").exists:
+            try:
+                path = "customer-master-key.txt"
+                file_bytes = os.urandom(96)
+                with Path.open(path, "wb") as f:
+                    f.write(file_bytes)
+            except Exception as e:
+                raise Exception(
+                    "Unable to write Customer Master Key to file due to the following error: "
+                ) from e
+
+        try:
+            path = "./customer-master-key.txt"
+            with Path.open(path, "rb") as f:
+                local_master_key = f.read()
+                if len(local_master_key) != 96:
+                    raise Exception("Expected the customer master key file to be 96 bytes.")
+                return {
+                    "local": {"key": local_master_key},
+                }
+        except Exception as e:
+            raise Exception(
+                "Unable to read Customer Master Key from file due to the following error: "
+            ) from e
+    else:
+        raise ValueError(
+            "Unrecognized value for kms_provider_name encountered while retrieving KMS credentials."
+        )
+
+
+def get_auto_encryption_options(kms_provider_name):
+    key_vault_database_name = "encryption"
+    key_vault_collection_name = "__keyVault"
+    key_vault_namespace = f"{key_vault_database_name}.{key_vault_collection_name}"
+    kms_provider_credentials = _get_kms_provider_credentials(kms_provider_name)
+    auto_encryption_opts = AutoEncryptionOpts(
+        kms_provider_credentials,
+        key_vault_namespace,
+        crypt_shared_lib_path=os.environ.get("SHARED_LIB_PATH"),
+    )
+    return urlencode(auto_encryption_opts)
+
+
 def parse_uri(uri, *, db_name=None, test=None):
     """
     Convert the given uri into a dictionary suitable for Django's DATABASES
diff --git a/tests/backend_/utils/test_parse_uri.py b/tests/backend_/utils/test_parse_uri.py
index 3198a4630..c5511baf8 100644
--- a/tests/backend_/utils/test_parse_uri.py
+++ b/tests/backend_/utils/test_parse_uri.py
@@ -1,10 +1,11 @@
 from unittest.mock import patch
+from urllib.parse import parse_qs
 
 import pymongo
 from django.core.exceptions import ImproperlyConfigured
 from django.test import SimpleTestCase
 
-from django_mongodb_backend import parse_uri
+from django_mongodb_backend import get_auto_encryption_options, parse_uri
 
 
 class ParseURITests(SimpleTestCase):
@@ -94,3 +95,10 @@ def test_invalid_credentials(self):
     def test_no_scheme(self):
         with self.assertRaisesMessage(pymongo.errors.InvalidURI, "Invalid URI scheme"):
             parse_uri("cluster0.example.mongodb.net")
+
+    def test_queryable_encryption_config(self):
+        auto_encryption_options = get_auto_encryption_options("local")
+        settings_dict = parse_uri(
+            f"mongodb://cluster0.example.mongodb.net/myDatabase{auto_encryption_options}"
+        )
+        self.assertEqual(settings_dict["OPTIONS"], parse_qs(auto_encryption_options))