[CMT2][BUG] Migrate from real to float, the data cannot be migrated

1 Create one table
create table real_type(real1 real);
insert into real_type values(999999999999999999999999999999999999999999999999999999999999999);
insert into real_type values(991111111111111111111111111111111111111111111111111111111111111);
insert into real_type values(991111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111);
insert into real_type values(99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999);

2 Do migration to offline
Actual result:
It will pop error as attachment.