set global innodb_defragment=1;
create table t1 (a int not null primary key auto_increment, b varchar(256), key second(a, b)) engine=innodb;
insert t1 select null, repeat('a', 256) from seq_1_to_100;
select count(*) from t1;
count(*)
100
start transaction;
select count(*) from t1;
count(*)
100
optimize table t1;
Table	Op	Msg_type	Msg_text
test.t1	optimize	status	OK
drop table t1;
set global innodb_defragment=default;