2 default.hits_10m_single CREATE TABLE hits2 ENGINE MergeTree PARTITION BY toYYYYMM(EventDate) ORDER BY (CounterID, EventDate, intHash32(UserID)) SAMPLE BY intHash32(UserID) SETTINGS parts_to_delay_insert = 5000, parts_to_throw_insert = 5000 AS -- don't select all columns to keep the run time down SELECT CounterID, EventDate, UserID, Title FROM hits_10m_single -- do not select anything because we only need column types LIMIT 0 SET max_insert_threads=8 SYSTEM STOP MERGES INSERT INTO hits2 SELECT CounterID, EventDate, UserID, Title FROM hits_10m_single SYSTEM START MERGES DROP TABLE IF EXISTS hits2