INSERT INTO function file(reading_from_file.parquet) SELECT URL FROM test.hits LIMIT 100000 SETTINGS engine_file_truncate_on_insert=1 SELECT sum(length(base58Encode(URL))) FROM file(reading_from_file.parquet) FORMAT Null INSERT INTO FUNCTION file(reading_from_file.parquet) SELECT * FROM numbers(0) SETTINGS engine_file_truncate_on_insert=1