-- Tags: long SET max_bytes_before_external_group_by = 100000000; SET max_memory_usage = 410000000; SET group_by_two_level_threshold = 100000; SET group_by_two_level_threshold_bytes = 50000000; SELECT sum(k), sum(c) FROM (SELECT number AS k, count() AS c FROM (SELECT * FROM system.numbers LIMIT 10000000) GROUP BY k); SELECT sum(k), sum(c), max(u) FROM (SELECT number AS k, count() AS c, uniqArray(range(number % 16)) AS u FROM (SELECT * FROM system.numbers LIMIT 1000000) GROUP BY k); SET max_memory_usage = 0; SET group_by_two_level_threshold = 100000; SET max_bytes_before_external_group_by = '1Mi'; -- method: key_string & key_string_two_level CREATE TABLE t_00284_str(s String) ENGINE = MergeTree() ORDER BY tuple(); INSERT INTO t_00284_str SELECT toString(number) FROM numbers_mt(1e6); INSERT INTO t_00284_str SELECT toString(number) FROM numbers_mt(1e6); SELECT s, count() FROM t_00284_str GROUP BY s ORDER BY s LIMIT 10 OFFSET 42; -- method: low_cardinality_key_string & low_cardinality_key_string_two_level CREATE TABLE t_00284_lc_str(s LowCardinality(String)) ENGINE = MergeTree() ORDER BY tuple(); INSERT INTO t_00284_lc_str SELECT toString(number) FROM numbers_mt(1e6); INSERT INTO t_00284_lc_str SELECT toString(number) FROM numbers_mt(1e6); SELECT s, count() FROM t_00284_lc_str GROUP BY s ORDER BY s LIMIT 10 OFFSET 42;