DROP TABLE IF EXISTS t_sparse_columns_clear; CREATE TABLE t_sparse_columns_clear (arr Array(UInt64), v UInt64) ENGINE = MergeTree ORDER BY tuple() SETTINGS ratio_of_defaults_for_sparse_serialization = 0.9, min_bytes_for_wide_part=0; INSERT INTO t_sparse_columns_clear SELECT [number], 0 FROM numbers(1000); SELECT column, serialization_kind FROM system.parts_columns WHERE database = currentDatabase() AND table = 't_sparse_columns_clear' AND active ORDER BY column; SET mutations_sync = 2; SET alter_sync = 2; ALTER TABLE t_sparse_columns_clear CLEAR COLUMN v; SELECT column, serialization_kind FROM system.parts_columns WHERE database = currentDatabase() AND table = 't_sparse_columns_clear' AND active ORDER BY column; OPTIMIZE TABLE t_sparse_columns_clear FINAL; SELECT column, serialization_kind FROM system.parts_columns WHERE database = currentDatabase() AND table = 't_sparse_columns_clear' AND active ORDER BY column; DROP TABLE t_sparse_columns_clear SYNC; SYSTEM FLUSH LOGS; SELECT count(), groupArray(message) FROM system.text_log WHERE logger_name LIKE '%' || currentDatabase() || '.t_sparse_columns_clear' || '%' AND level = 'Error';