INTPYTHON-698 Allow defining embedded model indexes on the top-level model

django_mongodb_backend/expressions/builtins.py

@@ -25,6 +25,7 @@
     Value,
     When,
 )
+from django.db.models.indexes import IndexExpression
 from django.db.models.sql import Query
 
 from django_mongodb_backend.query_utils import process_lhs
@@ -106,6 +107,19 @@ def expression_wrapper(self, compiler, connection):
     return self.expression.as_mql(compiler, connection, as_expr=True)
 
 
+def index_expression(self, compiler, connection, as_expr=False):  # noqa: ARG001
+    result = []
+    for expr in self.get_source_expressions():
+        if expr is None:
+            continue
+        for sub_expr in expr.get_source_expressions():
+            try:
+                result.append(sub_expr.as_mql(compiler, connection))
+            except FullResultSet:
+                result.append(Value(True).as_mql(compiler, connection))
+    return result
+
+
 def negated_expression(self, compiler, connection):
     return {"$not": expression_wrapper(self, compiler, connection)}
 
@@ -244,6 +258,7 @@ def register_expressions():
     Exists.as_mql_expr = exists
     ExpressionList.as_mql = process_lhs
     ExpressionWrapper.as_mql_expr = expression_wrapper
+    IndexExpression.as_mql = index_expression
     NegatedExpression.as_mql_expr = negated_expression
     OrderBy.as_mql_expr = partialmethod(order_by, as_expr=True)
     OrderBy.as_mql_path = partialmethod(order_by, as_expr=False)

django_mongodb_backend/features.py

@@ -99,6 +99,9 @@ class DatabaseFeatures(GISFeatures, BaseDatabaseFeatures):
         "model_fields.test_jsonfield.TestSaveLoad.test_bulk_update_custom_get_prep_value",
         # To debug: https://github.com/mongodb/django-mongodb-backend/issues/362
         "constraints.tests.UniqueConstraintTests.test_validate_case_when",
+        # Simple expression index are supported
+        "schema.tests.SchemaTests.test_func_unique_constraint_unsupported",
+        "schema.tests.SchemaTests.test_func_index_unsupported",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {

django_mongodb_backend/fields/embedded_model.py

@@ -211,6 +211,9 @@ def as_mql_path(self, compiler, connection):
     def output_field(self):
         return self._field
 
+    def db_type(self, connection):
+        return self.output_field.db_type(connection)
+
     @property
     def can_use_path(self):
         return self.is_simple_column

django_mongodb_backend/indexes.py

@@ -4,6 +4,7 @@
 from django.core.checks import Error, Warning
 from django.db import NotSupportedError
 from django.db.models import FloatField, Index, IntegerField
+from django.db.models.expressions import OrderBy
 from django.db.models.lookups import BuiltinLookup
 from django.db.models.sql.query import Query
 from django.db.models.sql.where import AND, XOR, WhereNode
@@ -46,10 +47,29 @@ def builtin_lookup_idx(self, compiler, connection):
 
 def get_pymongo_index_model(self, model, schema_editor, field=None, unique=False, column_prefix=""):
     """Return a pymongo IndexModel for this Django Index."""
+    filter_expression = defaultdict(dict)
+    expressions_fields = []
     if self.contains_expressions:
-        return None
+        query = Query(model=model, alias_cols=False)
+        compiler = query.get_compiler(connection=schema_editor.connection)
+        for expression in self.expressions:
+            field_ = expression.resolve_expression(query)
+            column = field_.as_mql(compiler, schema_editor.connection)
+            db_type = (
+                field_.expression.db_type(schema_editor.connection)
+                if isinstance(field_, OrderBy)
+                else field_.output_field.db_type(schema_editor.connection)
+            )
+            if unique:
+                filter_expression[column].update({"$type": db_type})
+            order = (
+                DESCENDING
+                if isinstance(expression, OrderBy) and expression.descending
+                else ASCENDING
+            )
+            expressions_fields.append((column, order))
+
     kwargs = {}
-    filter_expression = defaultdict(dict)
     if self.condition:
         filter_expression.update(self._get_condition_mql(model, schema_editor))
     if unique:
@@ -80,7 +100,7 @@ def get_pymongo_index_model(self, model, schema_editor, field=None, unique=False
             for field_name, order in self.fields_orders
         ]
     )
-    return IndexModel(index_orders, name=self.name, **kwargs)
+    return IndexModel(expressions_fields + index_orders, name=self.name, **kwargs)
 
 
 def where_node_idx(self, compiler, connection):

django_mongodb_backend/schema.py

@@ -2,6 +2,7 @@
 
 from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.models import Index, UniqueConstraint
+from django.db.models.expressions import F, OrderBy
 from pymongo.operations import SearchIndexModel
 
 from django_mongodb_backend.indexes import SearchIndex
@@ -351,6 +352,35 @@ def _remove_field_index(self, model, field, column_prefix=""):
             )
         collection.drop_index(index_names[0])
 
+    def _check_expression_indexes_applicable(self, expressions):
+        return all(
+            isinstance(expression.expression if isinstance(expression, OrderBy) else expression, F)
+            for expression in expressions
+        )
+
+    def _unique_supported(
+        self,
+        condition=None,
+        deferrable=None,
+        include=None,
+        expressions=None,
+        nulls_distinct=None,
+    ):
+        return (
+            (not condition or self.connection.features.supports_partial_indexes)
+            and (not deferrable or self.connection.features.supports_deferrable_unique_constraints)
+            and (not include or self.connection.features.supports_covering_indexes)
+            and (
+                not expressions
+                or self.connection.features.supports_expression_indexes
+                or self._check_expression_indexes_applicable(expressions)
+            )
+            and (
+                nulls_distinct is None
+                or self.connection.features.supports_nulls_distinct_unique_constraints
+            )
+        )
+
     @ignore_embedded_models
     def add_constraint(self, model, constraint, field=None, column_prefix="", parent_model=None):
         if isinstance(constraint, UniqueConstraint) and self._unique_supported(
@@ -361,6 +391,7 @@ def add_constraint(self, model, constraint, field=None, column_prefix="", parent
             nulls_distinct=constraint.nulls_distinct,
         ):
             idx = Index(
+                *constraint.expressions,
                 fields=constraint.fields,
                 name=constraint.name,
                 condition=constraint.condition,
@@ -391,6 +422,7 @@ def remove_constraint(self, model, constraint):
             nulls_distinct=constraint.nulls_distinct,
         ):
             idx = Index(
+                *constraint.expressions,
                 fields=constraint.fields,
                 name=constraint.name,
                 condition=constraint.condition,

docs/releases/5.2.x.rst

@@ -10,7 +10,11 @@ Django MongoDB Backend 5.2.x
 New features
 ------------
 
-- ...
+- Added support for creating indexes from expressions.
+  Currently, only ``F()`` expressions are supported to reference top-level
+  model fields inside embedded models.
+
+
 
 Bug fixes
 ---------

docs/topics/index.rst

@@ -11,3 +11,4 @@ know:
    embedded-models
    transactions
    known-issues
+   indexes

docs/topics/indexes.rst

@@ -0,0 +1,22 @@
+Indexes from Expressions
+========================
+
+Django MongoDB Backend now supports creating indexes from expressions.
+Currently, only ``F()`` expressions are supported, which allows referencing
+fields from the top-level model inside embedded fields.
+
+Example::
+
+    from django.db import models
+    from django.db.models import F
+
+    class Author(models.EmbeddedModel):
+        name = models.CharField()
+
+    class Book(models.Model):
+        author = models.EmbeddedField(Author)
+
+        class Meta:
+            indexes = [
+                models.Index(F("author__name")),
+            ]

tests/schema_/test_embedded_model.py

@@ -1,6 +1,7 @@
 import itertools
 
 from django.db import connection, models
+from django.db.models.expressions import F
 from django.test import TransactionTestCase, skipUnlessDBFeature
 from django.test.utils import isolate_apps
 
@@ -519,6 +520,167 @@ class Meta:
         self.assertTableNotExists(Author)
 
 
+class EmbeddedModelsTopLevelIndexTest(TestMixin, TransactionTestCase):
+    @isolate_apps("schema_")
+    def test_unique_together(self):
+        """Meta.unique_together defined at the top-level for embedded fields."""
+
+        class Address(EmbeddedModel):
+            unique_together_one = models.CharField(max_length=10)
+            unique_together_two = models.CharField(max_length=10)
+
+            class Meta:
+                app_label = "schema_"
+
+        class Author(EmbeddedModel):
+            address = EmbeddedModelField(Address)
+            unique_together_three = models.CharField(max_length=10)
+            unique_together_four = models.CharField(max_length=10)
+
+            class Meta:
+                app_label = "schema_"
+
+        class Book(models.Model):
+            author = EmbeddedModelField(Author)
+
+            class Meta:
+                app_label = "schema_"
+                constraints = [
+                    models.UniqueConstraint(
+                        F("author__unique_together_three").asc(),
+                        F("author__unique_together_four").desc(),
+                        name="unique_together_34",
+                    ),
+                    (
+                        models.UniqueConstraint(
+                            F("author__address__unique_together_one"),
+                            F("author__address__unique_together_two").asc(),
+                            name="unique_together_12",
+                        )
+                    ),
+                ]
+
+        with connection.schema_editor() as editor:
+            editor.create_model(Book)
+            self.assertTableExists(Book)
+            # Embedded uniques are created from top-level definition.
+            self.assertEqual(
+                self.get_constraints_for_columns(
+                    Book, ["author.unique_together_three", "author.unique_together_four"]
+                ),
+                ["unique_together_34"],
+            )
+            self.assertEqual(
+                self.get_constraints_for_columns(
+                    Book,
+                    ["author.address.unique_together_one", "author.address.unique_together_two"],
+                ),
+                ["unique_together_12"],
+            )
+            editor.delete_model(Book)
+        self.assertTableNotExists(Book)
+
+    @isolate_apps("schema_")
+    def test_add_remove_field_indexes(self):
+        """AddField/RemoveField + EmbeddedModelField + Meta.indexes at top-level."""
+
+        class Address(EmbeddedModel):
+            indexed_one = models.CharField(max_length=10)
+
+            class Meta:
+                app_label = "schema_"
+
+        class Author(EmbeddedModel):
+            address = EmbeddedModelField(Address)
+            indexed_two = models.CharField(max_length=10)
+
+            class Meta:
+                app_label = "schema_"
+
+        class Book(models.Model):
+            author = EmbeddedModelField(Author)
+
+            class Meta:
+                app_label = "schema_"
+                indexes = [
+                    models.Index(F("author__indexed_two").asc(), name="indexed_two"),
+                    models.Index(F("author__address__indexed_one").asc(), name="indexed_one"),
+                ]
+
+        new_field = EmbeddedModelField(Author)
+        new_field.set_attributes_from_name("author")
+
+        with connection.schema_editor() as editor:
+            # Create the table and add the field.
+            editor.create_model(Book)
+            editor.add_field(Book, new_field)
+            # Embedded indexes are created.
+            self.assertEqual(
+                self.get_constraints_for_columns(Book, ["author.indexed_two"]),
+                ["indexed_two"],
+            )
+            self.assertEqual(
+                self.get_constraints_for_columns(
+                    Book,
+                    ["author.address.indexed_one"],
+                ),
+                ["indexed_one"],
+            )
+            editor.delete_model(Book)
+        self.assertTableNotExists(Book)
+
+    @isolate_apps("schema_")
+    def test_add_remove_field_constraints(self):
+        """AddField/RemoveField + EmbeddedModelField + Meta.constraints at top-level."""
+
+        class Address(EmbeddedModel):
+            unique_constraint_one = models.CharField(max_length=10)
+
+            class Meta:
+                app_label = "schema_"
+
+        class Author(EmbeddedModel):
+            address = EmbeddedModelField(Address)
+            unique_constraint_two = models.CharField(max_length=10)
+
+            class Meta:
+                app_label = "schema_"
+
+        class Book(models.Model):
+            author = EmbeddedModelField(Author)
+
+            class Meta:
+                app_label = "schema_"
+                constraints = [
+                    models.UniqueConstraint(F("author__unique_constraint_two"), name="unique_two"),
+                    models.UniqueConstraint(
+                        F("author__address__unique_constraint_one"), name="unique_one"
+                    ),
+                ]
+
+        new_field = EmbeddedModelField(Author)
+        new_field.set_attributes_from_name("author")
+
+        with connection.schema_editor() as editor:
+            # Create the table and add the field.
+            editor.create_model(Book)
+            editor.add_field(Book, new_field)
+            # Embedded constraints are created.
+            self.assertEqual(
+                self.get_constraints_for_columns(Book, ["author.unique_constraint_two"]),
+                ["unique_two"],
+            )
+            self.assertEqual(
+                self.get_constraints_for_columns(
+                    Book,
+                    ["author.address.unique_constraint_one"],
+                ),
+                ["unique_one"],
+            )
+            editor.delete_model(Book)
+        self.assertTableNotExists(Book)
+
+
 class EmbeddedModelsIgnoredTests(TestMixin, TransactionTestCase):
     def test_embedded_not_created(self):
         """create_model() and delete_model() ignore EmbeddedModel."""