make SQLCompiler.get_columns() a cached property

django_mongodb/compiler.py

@@ -241,11 +241,10 @@ def execute_sql(
         self, result_type=MULTI, chunked_fetch=False, chunk_size=GET_ITERATOR_CHUNK_SIZE
     ):
         self.pre_sql_setup()
-        columns = self.get_columns()
         try:
             query = self.build_query(
                 # Avoid $project (columns=None) if unneeded.
-                columns
+                self.columns
                 if self.query.annotations or not self.query.default_cols or self.query.distinct
                 else None
             )
@@ -259,10 +258,10 @@ def execute_sql(
             except StopIteration:
                 return None  # No result
             else:
-                return self._make_result(obj, columns)
+                return self._make_result(obj, self.columns)
         # result_type is MULTI
         cursor.batch_size(chunk_size)
-        result = self.cursor_iter(cursor, chunk_size, columns)
+        result = self.cursor_iter(cursor, chunk_size, self.columns)
         if not chunked_fetch:
             # If using non-chunked reads, read data into memory.
             return list(result)
@@ -394,7 +393,8 @@ def build_query(self, columns=None):
         query.subqueries = self.subqueries
         return query
 
-    def get_columns(self):
+    @cached_property
+    def columns(self):
         """
         Return a tuple of (name, expression) with the columns and annotations
         which should be loaded by the query.
@@ -472,8 +472,7 @@ def get_combinator_queries(self):
             query.get_compiler(self.using, self.connection, self.elide_empty)
             for query in self.query.combined_queries
         ]
-        main_query_columns = self.get_columns()
-        main_query_fields, _ = zip(*main_query_columns, strict=True)
+        main_query_fields, _ = zip(*self.columns, strict=True)
         for compiler_ in compilers:
             try:
                 # If the columns list is limited, then all combined queries
@@ -490,7 +489,7 @@ def get_combinator_queries(self):
                     )
                 compiler_.pre_sql_setup()
                 compiler_.column_indices = self.column_indices
-                columns = compiler_.get_columns()
+                columns = compiler_.columns
                 parts.append((compiler_.build_query(columns), compiler_, columns))
             except EmptyResultSet:
                 # Omit the empty queryset with UNION.
@@ -528,7 +527,7 @@ def get_combinator_queries(self):
                 combinator_pipeline = inner_pipeline
         if not self.query.combinator_all:
             ids = defaultdict(dict)
-            for alias, expr in main_query_columns:
+            for alias, expr in self.columns:
                 # Unfold foreign fields.
                 if isinstance(expr, Col) and expr.alias != self.collection_name:
                     ids[expr.alias][expr.target.column] = expr.as_mql(self, self.connection)
@@ -633,10 +632,9 @@ def explain_query(self):
         )
         # Build the query pipeline.
         self.pre_sql_setup()
-        columns = self.get_columns()
         query = self.build_query(
             # Avoid $project (columns=None) if unneeded.
-            columns if self.query.annotations or not self.query.default_cols else None
+            self.columns if self.query.annotations or not self.query.default_cols else None
         )
         pipeline = query.get_pipeline()
         # Explain the pipeline.
@@ -796,7 +794,7 @@ def build_query(self, columns=None):
         compiler.pre_sql_setup(with_col_aliases=False)
         # Avoid $project (columns=None) if unneeded.
         columns = (
-            compiler.get_columns()
+            compiler.columns
             if self.query.annotations or not self.query.default_cols or self.query.distinct
             else None
         )

django_mongodb/expressions.py

@@ -98,10 +98,9 @@ def order_by(self, compiler, connection):
 def query(self, compiler, connection, lookup_name=None):
     subquery_compiler = self.get_compiler(connection=connection)
     subquery_compiler.pre_sql_setup(with_col_aliases=False)
-    columns = subquery_compiler.get_columns()
-    field_name, expr = columns[0]
+    field_name, expr = subquery_compiler.columns[0]
     subquery = subquery_compiler.build_query(
-        columns
+        subquery_compiler.columns
         if subquery_compiler.query.annotations or not subquery_compiler.query.default_cols
         else None
     )