INSERT INTO FUNCTION file(test_line_as_string.tsv) SELECT randomString(1000) FROM numbers(1000000) SETTINGS engine_file_truncate_on_insert=1 SELECT * FROM file(test_line_as_string.tsv, LineAsString) FORMAT Null INSERT INTO FUNCTION file(test_line_as_string.tsv) SELECT * FROM numbers(0) SETTINGS engine_file_truncate_on_insert=1