DROP TABLE IF EXISTS alter_bug;

create table alter_bug (
  epoch UInt64 CODEC(Delta,LZ4),
  _time_dec Float64
) Engine = MergeTree ORDER BY (epoch);


SELECT name, type, compression_codec FROM system.columns WHERE table='alter_bug' AND database=currentDatabase();

ALTER TABLE alter_bug MODIFY COLUMN epoch DEFAULT toUInt64(_time_dec) CODEC(Delta,LZ4);

SELECT name, type, default_expression, compression_codec FROM system.columns WHERE table='alter_bug' AND database=currentDatabase();

INSERT INTO alter_bug(_time_dec) VALUES(1577351080);

SELECT * FROM alter_bug;

DROP TABLE IF EXISTS alter_bug;