docstring.

Author: WaVEV

django_mongodb/compiler.py

@@ -55,8 +55,7 @@ def _prepare_expressions_for_pipeline(self, expression, target, count):
             column_target.set_attributes_from_name(alias)
             inner_column = Col(self.collection_name, column_target)
             if sub_expr.distinct:
-                inner_expr = sub_expr.as_mql(self, self.connection, force_filters=True)
-                rhs = next(iter(inner_expr.values()))
+                rhs = sub_expr.as_mql(self, self.connection, resolve_inner_expression=True)
                 group[alias] = {"$addToSet": rhs}
                 replacing_expr = sub_expr.copy()
                 replacing_expr.set_source_expressions([inner_column])

django_mongodb/functions.py

@@ -117,8 +117,13 @@ def cot(self, compiler, connection):
     return {"$divide": [1, {"$tan": lhs_mql}]}
 
 
-def count(self, compiler, connection, force_filters=False, **extra_context):  # noqa: ARG001
-    if not self.distinct or force_filters:
+def count(self, compiler, connection, resolve_inner_expression=False, **extra_context):  # noqa: ARG001
+    """
+    When resolve_inner_expression is True, it returns 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.
+    """
+    if not self.distinct or resolve_inner_expression:
         if self.filter:
             copy = self.copy()
             copy.filter = None
@@ -131,17 +136,21 @@ def count(self, compiler, connection, force_filters=False, **extra_context):  #
             condition = When(filter_, then=Value(1))
             copy.set_source_expressions([Case(condition)] + source_expressions[1:])
             node = copy
-            cond = process_lhs(node, compiler, connection)
+            inner_expression = process_lhs(node, compiler, connection)
         else:
             node = self
             lhs_mql = process_lhs(self, compiler, connection)
             null_cond = {"$in": [{"$type": lhs_mql}, ["missing", "null"]]}
-            cond = {
+            inner_expression = {
                 "$cond": {"if": null_cond, "then": None, "else": lhs_mql if self.distinct else 1}
             }
-        return {"$sum": cond}
+        if resolve_inner_expression:
+            return inner_expression
+        return {"$sum": inner_expression}
 
+    # When count is called with distinct without the flag, we sum the size of the set.
     lhs_mql = process_lhs(self, compiler, connection)
+    # And subtract 1 if None is in the set (it shouldn't have been counted).
     exits_null = {"$cond": {"if": {"$in": [{"$literal": None}, lhs_mql]}, "then": -1, "else": 0}}
     return {"$add": [{"$size": lhs_mql}, exits_null]}