doc edits

Author: timgraham

django_mongodb/aggregates.py

@@ -7,6 +7,7 @@
 
 from .query_utils import process_lhs
 
+# Aggregates whose MongoDB aggregation name differ from Aggregate.function.lower().
 MONGO_AGGREGATIONS = {Count: "sum"}
 
 
@@ -35,9 +36,9 @@ def aggregate(
 
 def count(self, compiler, connection, resolve_inner_expression=False, **extra_context):  # noqa: ARG001
     """
-    When resolve_inner_expression is True, return the argument as MQL that
-    resolves as a value. This is used to count different elements, so the inner
-    values are returned to be pushed into a set.
+    When resolve_inner_expression=True, return the MQL that resolves as a
+    value. This is used to count different elements, so the inner values are
+    returned to be pushed into a set.
     """
     if not self.distinct or resolve_inner_expression:
         if self.filter:
@@ -61,10 +62,10 @@ def count(self, compiler, connection, resolve_inner_expression=False, **extra_co
         if resolve_inner_expression:
             return inner_expression
         return {"$sum": inner_expression}
-    # If distinct=True or resolve_inner_expression=False, sum the size
-    # of the set.
+    # If distinct=True or resolve_inner_expression=False, sum the size of the
+    # set.
     lhs_mql = process_lhs(self, compiler, connection)
-    # Subtract 1 if None is in the set (it shouldn't have been counted).
+    # None shouldn't be counted, so subtract 1 if it's present.
     exits_null = {"$cond": {"if": {"$in": [{"$literal": None}, lhs_mql]}, "then": -1, "else": 0}}
     return {"$add": [{"$size": lhs_mql}, exits_null]}
 

django_mongodb/compiler.py

@@ -27,23 +27,20 @@ def __init__(self, *args, **kwargs):
         self.aggregation_pipeline = None
 
     def _get_group_alias_column(self, expr, annotation_group_idx):
-        """
-        Generate a dummy field for use in ids fields in $group.
-
-        If the column is a composite expression (not a single column),
-        it creates an auxiliary field and pass it through the flow.
-        When a foreign field is needed in the ids, escape the dot (.) using GROUP_SEPARATOR.
-        """
+        """Generate a dummy field for use in the ids fields in $group."""
         replacement = None
         if isinstance(expr, Col):
             col = expr
         else:
+            # If the column is a composite expression, creates a field for it.
             alias = f"__annotation_group{next(annotation_group_idx)}"
             col = self._get_column_from_expression(expr, alias)
             replacement = col
         if self.collection_name == col.alias:
             return col.target.column, replacement
-        return f"{col.alias}{self.GROUP_SEPARATOR}{col.target.column}", replacement
+        # If this is a foreign field, replace the normal dot (.) with
+        # GROUP_SEPARATOR since FieldPath field names may not contain '.'.
+        return f"{col.alias}.{col.target.column}", replacement
 
     def _get_column_from_expression(self, expr, alias):
         """