create table t1 (a float not null, primary key(a)) engine='InnoDB' 
partition by key (a) (
partition pa1 max_rows=20 min_rows=2,
partition pa2 max_rows=30 min_rows=3,
partition pa3 max_rows=30 min_rows=4,
partition pa4 max_rows=40 min_rows=2);
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` float NOT NULL,
  PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
 PARTITION BY KEY (`a`)
(PARTITION `pa1` MAX_ROWS = 20 MIN_ROWS = 2 ENGINE = InnoDB,
 PARTITION `pa2` MAX_ROWS = 30 MIN_ROWS = 3 ENGINE = InnoDB,
 PARTITION `pa3` MAX_ROWS = 30 MIN_ROWS = 4 ENGINE = InnoDB,
 PARTITION `pa4` MAX_ROWS = 40 MIN_ROWS = 2 ENGINE = InnoDB)
insert into t1 values (-3.402823466E+38), (3.402823466E+38), (-1.5), (-1), (0), (1), (1.5);
select * from t1;
a
-3.40282e38
-1.5
-1
0
1
1.5
3.40282e38
select * from t1 where a=1.5;
a
1.5
delete from t1 where a=1.5;
select * from t1;
a
-3.40282e38
-1.5
-1
0
1
3.40282e38
drop table t1;
create table t2 (a float not null, primary key(a)) engine='InnoDB' 
partition by key (a) partitions 10;
show create table t2;
Table	Create Table
t2	CREATE TABLE `t2` (
  `a` float NOT NULL,
  PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
 PARTITION BY KEY (`a`)
PARTITIONS 10
insert into t2 values (-3.402823466E+38), (-3.402823466E+37), (-123.456), (0), (1234546.789), (123.456), (1.5);
select * from t2;
a
-3.40282e38
-3.40282e37
-123.456
0
1.5
123.456
1234550
select * from t2 where a=123.456;
a
delete from t2 where a=123.456;
select * from t2;
a
-3.40282e38
-3.40282e37
-123.456
0
1.5
123.456
1234550
select * from t2 where a=1.5;
a
1.5
delete from t2 where a=1.5;
select * from t2;
a
-3.40282e38
-3.40282e37
-123.456
0
123.456
1234550
delete from t2;
1024*3 inserts;
select count(*) from t2;
count(*)
3072
drop table t2;