create table t(id int primary key);
set @@GLOBAL.DEBUG= '+d, before_sleep_in_flush_collect_stats';
set @@GLOBAL.DEBUG= '+d, after_sleep_in_flush_collect_stats';
#sending
set global xengine_force_flush_memtable_now=ON;;
set @@GLOBAL.DEBUG= '+d, sleep_before_rename_write_storage_engine';
alter table t add column c1 int;
set @@GLOBAL.DEBUG= '-d, sleep_before_rename_write_storage_engine';
set @@GLOBAL.DEBUG= '-d, before_sleep_in_flush_collect_stats';
set @@GLOBAL.DEBUG= '-d, after_sleep_in_flush_collect_stats';
drop table t;