add support for partial indexes

Co-authored-by: Emanuel Lupi <[email protected]>

Author: timgraham

.github/workflows/runtests.py

@@ -66,6 +66,7 @@
     "get_or_create",
     "i18n",
     "indexes",
+    "indexes_",
     "inline_formsets",
     "introspection",
     "invalid_models_tests",

django_mongodb/__init__.py

@@ -10,12 +10,14 @@
 from .expressions import register_expressions  # noqa: E402
 from .fields import register_fields  # noqa: E402
 from .functions import register_functions  # noqa: E402
+from .indexes import register_indexes  # noqa: E402
 from .lookups import register_lookups  # noqa: E402
 from .query import register_nodes  # noqa: E402
 
 register_aggregates()
 register_expressions()
 register_fields()
 register_functions()
+register_indexes()
 register_lookups()
 register_nodes()

django_mongodb/compiler.py

@@ -436,14 +436,31 @@ def project_field(column):
     @cached_property
     def base_table(self):
         return next(
-            v
-            for k, v in self.query.alias_map.items()
-            if isinstance(v, BaseTable) and self.query.alias_refcount[k]
+            (
+                v
+                for k, v in self.query.alias_map.items()
+                if isinstance(v, BaseTable) and self.query.alias_refcount[k]
+            ),
+            None,
         )
 
     @cached_property
     def collection_name(self):
-        return self.base_table.table_alias or self.base_table.table_name
+        if self.base_table:
+            return self.base_table.table_alias or self.base_table.table_name
+        # Use a dummy collection if the query doesn't specify a table.
+        # For Constraint.validate():
+        # SELECT 1 WHERE EXISTS(subquery checking if a constraint is violated)
+        # is translated as:
+        # [{"$facet": {"__null": []}},
+        #  {"$lookup": {"the subquery"}},
+        #  {"$match": {"condition to check from the subquery"}}]
+        query = self.query_class(self)
+        # The "__null" document is a placeholder so that the subquery has
+        # somewhere to return its results.
+        query.aggregation_pipeline = [{"$facet": {"__null": []}}]
+        self.subqueries.insert(0, query)
+        return "__null"
 
     @cached_property
     def collection(self):

django_mongodb/expressions.py

@@ -53,7 +53,9 @@ def case(self, compiler, connection):
 def col(self, compiler, connection):  # noqa: ARG001
     # If the column is part of a subquery and belongs to one of the parent
     # queries, it will be stored for reference using $let in a $lookup stage.
-    if (
+    # If the query is built with `alias_cols=False`, treat the column as
+    # belonging to the current collection.
+    if self.alias is not None and (
         self.alias not in compiler.query.alias_refcount
         or compiler.query.alias_refcount[self.alias] == 0
     ):
@@ -64,7 +66,8 @@ def col(self, compiler, connection):  # noqa: ARG001
             compiler.column_indices[self] = index
         return f"$${compiler.PARENT_FIELD_TEMPLATE.format(index)}"
     # Add the column's collection's alias for columns in joined collections.
-    prefix = f"{self.alias}." if self.alias != compiler.collection_name else ""
+    has_alias = self.alias and self.alias != compiler.collection_name
+    prefix = f"{self.alias}." if has_alias else ""
     return f"${prefix}{self.target.column}"
 
 

django_mongodb/features.py

@@ -1,3 +1,5 @@
+import operator
+
 from django.db.backends.base.features import BaseDatabaseFeatures
 from django.utils.functional import cached_property
 
@@ -21,12 +23,14 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_expression_indexes = False
     supports_foreign_keys = False
     supports_ignore_conflicts = False
+    # Before MongoDB 6.0, $in cannot be used in partialFilterExpression.
+    supports_in_index_operator = property(operator.attrgetter("is_mongodb_6_0"))
+    # Before MongoDB 6.0, $or cannot be used in partialFilterExpression.
+    supports_or_index_operator = property(operator.attrgetter("is_mongodb_6_0"))
     supports_json_field_contains = False
     # BSON Date type doesn't support microsecond precision.
     supports_microsecond_precision = False
     supports_paramstyle_pyformat = False
-    # Not implemented.
-    supports_partial_indexes = False
     supports_select_difference = False
     supports_select_intersection = False
     supports_sequence_reset = False
@@ -91,11 +95,16 @@ 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_partial_expression_in = {
+        "schema.tests.SchemaTests.test_remove_ignored_unique_constraint_not_create_fk_index",
+    }
 
     @cached_property
     def django_test_expected_failures(self):
         expected_failures = super().django_test_expected_failures
         expected_failures.update(self._django_test_expected_failures)
+        if not self.supports_in_index_operator:
+            expected_failures.update(self._django_test_expected_failures_partial_expression_in)
         if not self.is_mongodb_6_3:
             expected_failures.update(self._django_test_expected_failures_bitwise)
         return expected_failures
@@ -560,9 +569,6 @@ def django_test_expected_failures(self):
             # Probably something to do with lack of transaction support.
             "migration_test_data_persistence.tests.MigrationDataNormalPersistenceTestCase.test_persistence",
         },
-        "Partial indexes to be supported.": {
-            "indexes.tests.PartialIndexConditionIgnoredTests.test_condition_ignored",
-        },
         "Database caching not implemented.": {
             "cache.tests.CreateCacheTableForDBCacheTests",
             "cache.tests.DBCacheTests",
@@ -597,6 +603,10 @@ def django_test_expected_failures(self):
         },
     }
 
+    @cached_property
+    def is_mongodb_6_0(self):
+        return self.connection.get_database_version() >= (6, 0)
+
     @cached_property
     def is_mongodb_6_3(self):
         return self.connection.get_database_version() >= (6, 3)

django_mongodb/indexes.py

@@ -0,0 +1,74 @@
+from django.db import NotSupportedError
+from django.db.models import Index
+from django.db.models.fields.related_lookups import In
+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
+
+from .query_utils import process_rhs
+
+MONGO_INDEX_OPERATORS = {
+    "exact": "$eq",
+    "gt": "$gt",
+    "gte": "$gte",
+    "lt": "$lt",
+    "lte": "$lte",
+    "in": "$in",
+}
+
+
+def _get_condition_mql(self, model, schema_editor):
+    """Analogous to Index._get_condition_sql()."""
+    query = Query(model=model, alias_cols=False)
+    where = query.build_where(self.condition)
+    compiler = query.get_compiler(connection=schema_editor.connection)
+    return where.as_mql_idx(compiler, schema_editor.connection)
+
+
+def builtin_lookup_idx(self, compiler, connection):
+    lhs_mql = self.lhs.target.column
+    value = process_rhs(self, compiler, connection)
+    try:
+        operator = MONGO_INDEX_OPERATORS[self.lookup_name]
+    except KeyError:
+        raise NotSupportedError(
+            f"MongoDB does not support the '{self.lookup_name}' lookup in indexes."
+        ) from None
+    return {lhs_mql: {operator: value}}
+
+
+def in_idx(self, compiler, connection):
+    if not connection.features.supports_in_index_operator:
+        raise NotSupportedError("MongoDB < 6.0 does not support the 'in' lookup in indexes.")
+    return builtin_lookup_idx(self, compiler, connection)
+
+
+def where_node_idx(self, compiler, connection):
+    if self.connector == AND:
+        operator = "$and"
+    elif self.connector == XOR:
+        raise NotSupportedError("MongoDB does not support the '^' operator lookup in indexes.")
+    else:
+        if not connection.features.supports_in_index_operator:
+            raise NotSupportedError("MongoDB < 6.0 does not support the '|' operator in indexes.")
+        operator = "$or"
+    if self.negated:
+        raise NotSupportedError("MongoDB does not support the '~' operator in indexes.")
+    children_mql = []
+    for child in self.children:
+        mql = child.as_mql_idx(compiler, connection)
+        children_mql.append(mql)
+    if len(children_mql) == 1:
+        mql = children_mql[0]
+    elif len(children_mql) > 1:
+        mql = {operator: children_mql}
+    else:
+        mql = {}
+    return mql
+
+
+def register_indexes():
+    BuiltinLookup.as_mql_idx = builtin_lookup_idx
+    In.as_mql_idx = in_idx
+    Index._get_condition_mql = _get_condition_mql
+    WhereNode.as_mql_idx = where_node_idx

django_mongodb/schema.py

@@ -1,3 +1,5 @@
+from collections import defaultdict
+
 from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.models import Index, UniqueConstraint
 from pymongo import ASCENDING, DESCENDING
@@ -166,17 +168,23 @@ def add_index(self, model, index, field=None, unique=False):
         if index.contains_expressions:
             return
         kwargs = {}
+        filter_expression = defaultdict(dict)
+        if index.condition:
+            filter_expression.update(index._get_condition_mql(model, self))
         if unique:
-            filter_expression = {}
+            kwargs["unique"] = True
             # Indexing on $type matches the value of most SQL databases by
             # allowing multiple null values for the unique constraint.
             if field:
-                filter_expression[field.column] = {"$type": field.db_type(self.connection)}
+                filter_expression[field.column].update({"$type": field.db_type(self.connection)})
             else:
                 for field_name, _ in index.fields_orders:
                     field_ = model._meta.get_field(field_name)
-                    filter_expression[field_.column] = {"$type": field_.db_type(self.connection)}
-            kwargs = {"partialFilterExpression": filter_expression, "unique": True}
+                    filter_expression[field_.column].update(
+                        {"$type": field_.db_type(self.connection)}
+                    )
+        if filter_expression:
+            kwargs["partialFilterExpression"] = filter_expression
         index_orders = (
             [(field.column, ASCENDING)]
             if field
@@ -260,7 +268,11 @@ def add_constraint(self, model, constraint, field=None):
             expressions=constraint.expressions,
             nulls_distinct=constraint.nulls_distinct,
         ):
-            idx = Index(fields=constraint.fields, name=constraint.name)
+            idx = Index(
+                fields=constraint.fields,
+                name=constraint.name,
+                condition=constraint.condition,
+            )
             self.add_index(model, idx, field=field, unique=True)
 
     def _add_field_unique(self, model, field):
@@ -276,7 +288,11 @@ def remove_constraint(self, model, constraint):
             expressions=constraint.expressions,
             nulls_distinct=constraint.nulls_distinct,
         ):
-            idx = Index(fields=constraint.fields, name=constraint.name)
+            idx = Index(
+                fields=constraint.fields,
+                name=constraint.name,
+                condition=constraint.condition,
+            )
             self.remove_index(model, idx)
 
     def _remove_field_unique(self, model, field):

tests/indexes_/__init__.py

@@ -0,0 +1,7 @@
+from django.db import models
+
+
+class Article(models.Model):
+    headline = models.CharField(max_length=100)
+    number = models.IntegerField()
+    body = models.TextField()