add overlap lookup

django_mongodb/features.py

@@ -83,6 +83,9 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # contains with Exists() doesn't work:
         # https://github.com/mongodb-labs/django-mongodb/issues/204
         "model_fields_.test_arrayfield.QueryingTests.test_contains_subquery",
+        # overlap with values() returns no results:
+        # https://github.com/mongodb-labs/django-mongodb/issues/209
+        "model_fields_.test_arrayfield.QueryingTests.test_overlap_values",
         # icontains doesn't work on ArrayField:
         # Unsupported conversion from array to string in $convert
         "model_fields_.test_arrayfield.QueryingTests.test_icontains",

django_mongodb/fields/array.py

@@ -253,6 +253,18 @@ class ArrayExact(ArrayRHSMixin, Exact):
     pass
 
 
+@ArrayField.register_lookup
+class ArrayOverlap(ArrayRHSMixin, FieldGetDbPrepValueMixin, Lookup):
+    lookup_name = "overlap"
+
+    def as_mql(self, compiler, connection):
+        lhs_mql = process_lhs(self, compiler, connection)
+        value = process_rhs(self, compiler, connection)
+        return {
+            "$and": [{"$ne": [lhs_mql, None]}, {"$size": {"$setIntersection": [value, lhs_mql]}}]
+        }
+
+
 @ArrayField.register_lookup
 class ArrayLenTransform(Transform):
     lookup_name = "len"

docs/source/fields.rst

@@ -106,6 +106,26 @@ data. It uses the ``$setIntersection`` operator. For example:
     >>> Post.objects.filter(tags__contains=["django", "thoughts"])
     <QuerySet [<Post: First post>]>
 
+.. fieldlookup:: arrayfield.overlap
+
+``overlap``
+~~~~~~~~~~~
+
+Returns objects where the data shares any results with the values passed. It
+uses the ``$setIntersection`` operator. For example:
+
+.. code-block:: pycon
+
+    >>> Post.objects.create(name="First post", tags=["thoughts", "django"])
+    >>> Post.objects.create(name="Second post", tags=["thoughts", "tutorial"])
+    >>> Post.objects.create(name="Third post", tags=["tutorial", "django"])
+
+    >>> Post.objects.filter(tags__overlap=["thoughts"])
+    <QuerySet [<Post: First post>, <Post: Second post>]>
+
+    >>> Post.objects.filter(tags__overlap=["thoughts", "tutorial"])
+    <QuerySet [<Post: First post>, <Post: Second post>, <Post: Third post>]>
+
 .. fieldlookup:: arrayfield.len
 
 ``len``

tests/model_fields_/test_arrayfield.py

@@ -10,6 +10,7 @@
 from django.core.management import call_command
 from django.db import IntegrityError, connection, models
 from django.db.models.expressions import Exists, OuterRef, Value
+from django.db.models.functions import Upper
 from django.test import (
     SimpleTestCase,
     TestCase,
@@ -369,6 +370,38 @@ def test_icontains(self):
     def test_contains_charfield(self):
         self.assertSequenceEqual(CharArrayModel.objects.filter(field__contains=["text"]), [])
 
+    def test_overlap_charfield(self):
+        self.assertSequenceEqual(CharArrayModel.objects.filter(field__overlap=["text"]), [])
+
+    def test_overlap_charfield_including_expression(self):
+        obj_1 = CharArrayModel.objects.create(field=["TEXT", "lower text"])
+        obj_2 = CharArrayModel.objects.create(field=["lower text", "TEXT"])
+        CharArrayModel.objects.create(field=["lower text", "text"])
+        self.assertSequenceEqual(
+            CharArrayModel.objects.filter(
+                field__overlap=[
+                    Upper(Value("text")),
+                    "other",
+                ]
+            ),
+            [obj_1, obj_2],
+        )
+
+    def test_overlap_values(self):
+        qs = NullableIntegerArrayModel.objects.filter(order__lt=3)
+        self.assertCountEqual(
+            NullableIntegerArrayModel.objects.filter(
+                field__overlap=qs.values_list("field"),
+            ),
+            self.objs[:3],
+        )
+        self.assertCountEqual(
+            NullableIntegerArrayModel.objects.filter(
+                field__overlap=qs.values("field"),
+            ),
+            self.objs[:3],
+        )
+
     def test_index(self):
         self.assertSequenceEqual(
             NullableIntegerArrayModel.objects.filter(field__0=2), self.objs[1:3]
@@ -389,6 +422,12 @@ def test_index_used_on_nested_data(self):
             NestedIntegerArrayModel.objects.filter(field__0=[1, 2]), [instance]
         )
 
+    def test_overlap(self):
+        self.assertSequenceEqual(
+            NullableIntegerArrayModel.objects.filter(field__overlap=[1, 2]),
+            self.objs[0:3],
+        )
+
     def test_index_annotation(self):
         qs = NullableIntegerArrayModel.objects.annotate(second=models.F("field__1"))
         self.assertCountEqual(