fix GenericRelation object_id / target id join type mismatch

Author: WaVEV

django_mongodb/features.py

@@ -87,26 +87,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "backends.tests.ThreadTests.test_pass_connection_between_threads",
         "backends.tests.ThreadTests.test_closing_non_shared_connections",
         "backends.tests.ThreadTests.test_default_connection_thread_local",
-        # GenericRelation join doesn't work due to type mismatch between
-        # object_id (string) and target id (ObjectId) field.
-        "generic_relations.tests.GenericRelationsTests.test_subclasses_with_gen_rel",
-        "generic_relations.tests.GenericRelationsTests.test_subclasses_with_parent_gen_rel",
-        "generic_relations.tests.ProxyRelatedModelTest.test_query",
-        "generic_relations.tests.ProxyRelatedModelTest.test_query_proxy",
-        "generic_relations.tests.GenericRelationsTests.test_access_via_content_type",
-        "generic_relations.tests.GenericRelationsTests.test_generic_relation_to_inherited_child",
-        "generic_relations.tests.GenericRelationsTests.test_query_content_object",
-        "generic_relations_regress.tests.GenericRelationTests.test_filter_on_related_proxy_model",
-        "generic_relations_regress.tests.GenericRelationTests.test_charlink_filter",
-        "generic_relations_regress.tests.GenericRelationTests.test_filter_targets_related_pk",
-        "generic_relations_regress.tests.GenericRelationTests.test_generic_reverse_relation_exclude_filter",
-        "generic_relations_regress.tests.GenericRelationTests.test_generic_reverse_relation_with_abc",
-        "generic_relations_regress.tests.GenericRelationTests.test_generic_reverse_relation_with_mti",
-        "generic_relations_regress.tests.GenericRelationTests.test_reverse_relation_pk",
-        "generic_relations_regress.tests.GenericRelationTests.test_textlink_filter",
-        "generic_relations_regress.tests.GenericRelationTests.test_ticket_20378",
-        "generic_relations_regress.tests.GenericRelationTests.test_ticket_20564",
-        "generic_relations_regress.tests.GenericRelationTests.test_ticket_20564_nullable_fk",
         # AddField
         "schema.tests.SchemaTests.test_add_indexed_charfield",
         "schema.tests.SchemaTests.test_add_unique_charfield",

django_mongodb/operations.py

@@ -8,7 +8,9 @@
 from django.conf import settings
 from django.db import DataError
 from django.db.backends.base.operations import BaseDatabaseOperations
+from django.db.models import TextField
 from django.db.models.expressions import Combinable
+from django.db.models.functions import Cast
 from django.utils import timezone
 from django.utils.regex_helper import _lazy_re_compile
 
@@ -212,6 +214,18 @@ def explain_query_prefix(self, format=None, **options):
         super().explain_query_prefix(format, **options)
         return validated_options
 
+    def prepare_join_on_clause(self, lhs_table, lhs_field, rhs_table, rhs_field):
+        lhs_expr, rhs_expr = super().prepare_join_on_clause(
+            lhs_table, lhs_field, rhs_table, rhs_field
+        )
+        # If the types are different, cast both to string.
+        if lhs_field.db_type(self.connection) != rhs_field.db_type(self.connection):
+            if lhs_field.db_type(self.connection) != "string":
+                lhs_expr = Cast(lhs_expr, output_field=TextField())
+            if rhs_field.db_type(self.connection) != "string":
+                rhs_expr = Cast(rhs_expr, output_field=TextField())
+        return lhs_expr, rhs_expr
+
     """Django uses these methods to generate SQL queries before it generates MQL queries."""
 
     # EXTRACT format cannot be passed in parameters.

django_mongodb/query.py

@@ -99,12 +99,12 @@ def join(self, compiler, connection):
     # Add a join condition for each pair of joining fields.
     for lhs, rhs in self.join_fields:
         lhs, rhs = connection.ops.prepare_join_on_clause(
-            self.parent_alias, lhs, self.table_name, rhs
+            self.parent_alias, lhs, compiler.collection_name, rhs
         )
         lhs_fields.append(lhs.as_mql(compiler, connection))
         # In the lookup stage, the reference to this column doesn't include
         # the collection name.
-        rhs_fields.append(rhs.as_mql(compiler, connection).replace(f"{self.table_name}.", "", 1))
+        rhs_fields.append(rhs.as_mql(compiler, connection))
 
     parent_template = "parent__field__"
     lookup_pipeline = [