DROP TABLE IF EXISTS test.hits_dst; DROP TABLE IF EXISTS test.hits_buffer; CREATE TABLE test.hits_dst AS test.hits ENGINE = MergeTree PARTITION BY toYYYYMM(EventDate) ORDER BY (CounterID, EventDate, intHash32(UserID)) SAMPLE BY intHash32(UserID) SETTINGS storage_policy = 'default'; CREATE TABLE test.hits_buffer AS test.hits_dst ENGINE = Buffer(test, hits_dst, 8, 600, 600, 1000000, 1000000, 100000000, 1000000000); INSERT INTO test.hits_buffer SELECT * FROM test.hits WHERE CounterID = 800784; SELECT count() FROM test.hits_buffer; SELECT count() FROM test.hits_dst; OPTIMIZE TABLE test.hits_buffer; SELECT count() FROM test.hits_buffer; SELECT count() FROM test.hits_dst; DROP TABLE test.hits_dst; DROP TABLE test.hits_buffer;