Fix pipeline position of unionWith.

Author: WaVEV

django_mongodb_backend/compiler.py

@@ -40,6 +40,8 @@ def __init__(self, *args, **kwargs):
         self.search_pipeline = []
         # The aggregation has no group-by fields and needs wrapping.
         self.wrap_for_global_aggregation = False
+        # HAVING stage match (MongoDB equivalent)
+        self.having_match_mql = None
 
     def _get_group_alias_column(self, expr, annotation_group_idx):
         """Generate a dummy field for use in the ids fields in $group."""
@@ -324,7 +326,7 @@ def pre_sql_setup(self, with_col_aliases=False):
                     pipeline.extend(query.get_pipeline())
                 # Remove the added subqueries.
                 self.subqueries = []
-                pipeline.append({"$match": having})
+                self.having_match_mql = having
             self.aggregation_pipeline = pipeline
         self.annotations = {
             target: expr.replace_expressions(all_replacements)

django_mongodb_backend/query.py

@@ -50,6 +50,7 @@ def __init__(self, compiler):
         self.lookup_pipeline = None
         self.project_fields = None
         self.aggregation_pipeline = compiler.aggregation_pipeline
+        self.having = compiler.having_match_mql
         self.search_pipeline = compiler.search_pipeline
         self.extra_fields = None
         self.combinator_pipeline = None
@@ -95,6 +96,8 @@ def get_pipeline(self):
         if self.wrap_for_global_aggregation:
             # Add an empty extra document to handle default values on empty results
             pipeline.append({"$unionWith": {"pipeline": [{"$documents": [{}]}]}})
+        if self.having:
+            pipeline.append({"$match": self.having})
         if self.project_fields:
             pipeline.append({"$project": self.project_fields})
         if self.combinator_pipeline: