DROP TABLE IF EXISTS empty_summing; set allow_deprecated_syntax_for_merge_tree=1; CREATE TABLE empty_summing (d Date, k UInt64, v Int8) ENGINE=SummingMergeTree(d, k, 8192); INSERT INTO empty_summing VALUES ('2015-01-01', 1, 10); INSERT INTO empty_summing VALUES ('2015-01-01', 1, -10); OPTIMIZE TABLE empty_summing; SELECT * FROM empty_summing; INSERT INTO empty_summing VALUES ('2015-01-01', 1, 4),('2015-01-01', 2, -9),('2015-01-01', 3, -14); INSERT INTO empty_summing VALUES ('2015-01-01', 1, -2),('2015-01-01', 1, -2),('2015-01-01', 3, 14); INSERT INTO empty_summing VALUES ('2015-01-01', 1, 0),('2015-01-01', 3, 0); OPTIMIZE TABLE empty_summing; SELECT * FROM empty_summing; DROP TABLE empty_summing;