From b480548dcab4cd458544bc7166894b688a2c2e48 Mon Sep 17 00:00:00 2001
From: Emanuel Lupi <emanuel.lupi91@gmail.com>
Date: Thu, 20 Nov 2025 01:28:23 -0300
Subject: [PATCH 1/2] Remove $facet in top level group stages

---
 django_mongodb_backend/aggregates.py |  1 +
 django_mongodb_backend/compiler.py   | 18 ++++--------------
 2 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/django_mongodb_backend/aggregates.py b/django_mongodb_backend/aggregates.py
index fb41ce4fc..9921e34ab 100644
--- a/django_mongodb_backend/aggregates.py
+++ b/django_mongodb_backend/aggregates.py
@@ -52,6 +52,7 @@ def count(self, compiler, connection, resolve_inner_expression=False):
     # If distinct=True or resolve_inner_expression=False, sum the size of the
     # set.
     lhs_mql = process_lhs(self, compiler, connection, as_expr=True)
+    lhs_mql = {"$ifNull": [lhs_mql, []]}
     # None shouldn't be counted, so subtract 1 if it's present.
     exits_null = {"$cond": {"if": {"$in": [{"$literal": None}, lhs_mql]}, "then": -1, "else": 0}}
     return {"$add": [{"$size": lhs_mql}, exits_null]}
diff --git a/django_mongodb_backend/compiler.py b/django_mongodb_backend/compiler.py
index cb867221e..6feb7b13e 100644
--- a/django_mongodb_backend/compiler.py
+++ b/django_mongodb_backend/compiler.py
@@ -235,20 +235,10 @@ def _build_aggregation_pipeline(self, ids, group):
         pipeline = []
         if not ids:
             group["_id"] = None
-            pipeline.append({"$facet": {"group": [{"$group": group}]}})
-            pipeline.append(
-                {
-                    "$addFields": {
-                        key: {
-                            "$getField": {
-                                "input": {"$arrayElemAt": ["$group", 0]},
-                                "field": key,
-                            }
-                        }
-                        for key in group
-                    }
-                }
-            )
+            pipeline.append({"$group": group})
+            # It may be a bug, $$NOW has to be called to be reachable in the rest of the pipeline.
+            pipeline.append({"$set": {"__now": "$$NOW"}})
+            pipeline.append({"$unionWith": {"pipeline": [{"$documents": [{}]}]}})
         else:
             group["_id"] = ids
             pipeline.append({"$group": group})

From 273957fd5953d4e9b4b195fde8b255794519e783 Mon Sep 17 00:00:00 2001
From: Emanuel Lupi <emanuel.lupi91@gmail.com>
Date: Tue, 25 Nov 2025 00:22:27 -0300
Subject: [PATCH 2/2] Wrap query for global aggregation

---
 django_mongodb_backend/compiler.py |  8 +++-----
 django_mongodb_backend/query.py    | 17 +++++++++++++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/django_mongodb_backend/compiler.py b/django_mongodb_backend/compiler.py
index 6feb7b13e..1388e9ba7 100644
--- a/django_mongodb_backend/compiler.py
+++ b/django_mongodb_backend/compiler.py
@@ -38,6 +38,7 @@ def __init__(self, *args, **kwargs):
         self.subqueries = []
         # Atlas search stage.
         self.search_pipeline = []
+        self.wrap_for_global_aggregation = False
 
     def _get_group_alias_column(self, expr, annotation_group_idx):
         """Generate a dummy field for use in the ids fields in $group."""
@@ -234,11 +235,8 @@ def _build_aggregation_pipeline(self, ids, group):
         """Build the aggregation pipeline for grouping."""
         pipeline = []
         if not ids:
-            group["_id"] = None
-            pipeline.append({"$group": group})
-            # It may be a bug, $$NOW has to be called to be reachable in the rest of the pipeline.
-            pipeline.append({"$set": {"__now": "$$NOW"}})
-            pipeline.append({"$unionWith": {"pipeline": [{"$documents": [{}]}]}})
+            pipeline.append({"$group": {"_id": None, **group}})
+            self.wrap_for_global_aggregation = True
         else:
             group["_id"] = ids
             pipeline.append({"$group": group})
diff --git a/django_mongodb_backend/query.py b/django_mongodb_backend/query.py
index 5b4f0ec51..85cf0c774 100644
--- a/django_mongodb_backend/query.py
+++ b/django_mongodb_backend/query.py
@@ -56,6 +56,7 @@ def __init__(self, compiler):
         # $lookup stage that encapsulates the pipeline for performing a nested
         # subquery.
         self.subquery_lookup = None
+        self.wrap_for_global_aggregation = compiler.wrap_for_global_aggregation
 
     def __repr__(self):
         return f"<MongoQuery: {self.match_mql!r} ORDER {self.ordering!r}>"
@@ -91,6 +92,22 @@ def get_pipeline(self):
             pipeline.append({"$match": self.match_mql})
         if self.aggregation_pipeline:
             pipeline.extend(self.aggregation_pipeline)
+        if self.wrap_for_global_aggregation:
+            pipeline = [
+                {"$collStats": {}},
+                {
+                    "$lookup": {
+                        "from": self.compiler.collection_name,
+                        "as": "wrapped",
+                        "pipeline": pipeline,
+                    }
+                },
+                {
+                    "$replaceWith": {
+                        "$cond": [{"$eq": ["$wrapped", []]}, {}, {"$first": "$wrapped"}]
+                    }
+                },
+            ]
         if self.project_fields:
             pipeline.append({"$project": self.project_fields})
         if self.combinator_pipeline: