DROP TABLE IF EXISTS perf_lc_fixed_str_groupby CREATE TABLE perf_lc_fixed_str_groupby( a LowCardinality(FixedString(14)), b LowCardinality(FixedString(14)) ) ENGINE MergeTree ORDER BY tuple() INSERT INTO perf_lc_fixed_str_groupby SELECT ('number key ' || toString(number % 400)) AS a, ('number key ' || toString(number % 20)) AS b FROM numbers(30000000) SELECT count() FROM perf_lc_fixed_str_groupby GROUP BY a FORMAT Null SELECT count() FROM perf_lc_fixed_str_groupby GROUP BY b FORMAT Null DROP TABLE IF EXISTS perf_lc_fixed_str_groupby