Update app/mapper.py

app/mapper.py

@@ -45,7 +45,8 @@ def ensure_canonical_table(duck: duckdb.DuckDBPyConnection, df: pd.DataFrame) ->
     """)
     
     # Get existing columns (lowercase for comparison)
-    existing_cols_raw = duck.execute(f"PRAGMA table_info('{table_name}')").fetchall()existing_cols = {str(r[0]).lower() for r in existing_cols_raw}  # ✅ FORCE STRING
+    existing_cols_raw = duck.execute(f"PRAGMA table_info('{table_name}')").fetchall()
+    existing_cols = {str(r[0]).lower() for r in existing_cols_raw}  
     
     # ✅ BULLETPROOF: Add missing columns with safe name handling
     for col in df.columns: