SNOW-2356876: Set cte_optimization_enabled to True for all Snowpark pandas sessions (#3815)

Author: sfc-gh-helmeleegy

CHANGELOG.md

@@ -140,6 +140,7 @@
 - When hybrid execution is enabled, `pd.merge`, `pd.concat`, `DataFrame.merge`, and `DataFrame.join` may now move arguments to backends other than those among the function arguments.
 - Improved performance of `DataFrame.to_snowflake` and `pd.to_snowflake(dataframe)` for large data by uploading data via a parquet file. You can control the dataset size at which Snowpark pandas switches to parquet with the variable `modin.config.PandasToSnowflakeParquetThresholdBytes`.
 - Improved performance of `Series.to_snowflake` and `pd.to_snowflake(series)` for large data by uploading data via a parquet file. You can control the dataset size at which Snowpark pandas switches to parquet with the variable `modin.config.PandasToSnowflakeParquetThresholdBytes`.
+- Set `cte_optimization_enabled` to True for all Snowpark pandas sessions.
 
 ## 1.39.1 (2025-09-25)
 

src/snowflake/snowpark/modin/plugin/_internal/session.py

@@ -81,6 +81,7 @@ def _get_active_session(self) -> Session:
             self._warn_if_possible_when_quoted_identifiers_ignore_case_is_set(
                 self._session
             )
+            self._session.cte_optimization_enabled = True
             return self._session
 
         try:
@@ -89,6 +90,7 @@ def _get_active_session(self) -> Session:
             self._warn_if_possible_when_quoted_identifiers_ignore_case_is_set(
                 self._session
             )
+            session.cte_optimization_enabled = True
             return session
         except SnowparkSessionException as ex:
             if ex.error_code == "1409":

tests/integ/modin/test_session_cte_optimization.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2012-2025 Snowflake Computing Inc. All rights reserved.
+#
+
+from snowflake.snowpark.session import _get_active_session
+
+from tests.integ.utils.sql_counter import sql_count_checker
+
+
+@sql_count_checker(query_count=0)
+def test_cte_optimization_for_snowpark_pandas(db_parameters):
+    session = _get_active_session()
+
+    # Preserve original setting
+    cte_optimization_original = session.cte_optimization_enabled
+
+    # Ensure cte optimization is disabled for current session
+    session.cte_optimization_enabled = False
+    assert session.cte_optimization_enabled is False
+
+    # Import Snowpark pandas
+    import modin.pandas as pd
+    import snowflake.snowpark.modin.plugin  # noqa: F401
+
+    # Verify that cte optimization will now be enabled
+    assert pd.session == session
+    assert pd.session.cte_optimization_enabled is True
+
+    # Revert to original setting
+    session.cte_optimizatin_enabled = cte_optimization_original
+    assert session.cte_optimizatin_enabled == cte_optimization_original