DROP TABLE IF EXISTS test.tab; CREATE TABLE test.tab (date Date, value UInt64, s String, m FixedString(16)) ENGINE = MergeTree(date, (date, value), 8); INSERT INTO test.tab SELECT today() as date, number as value, '' as s, toFixedString('', 16) as m from system.numbers limit 42; SET preferred_max_column_in_block_size_bytes = 32; SELECT blockSize(), * from test.tab format Null; SELECT 0;