Mysql insert the lock is how to determine the scope of intention?-CodePudding

For example:

 CREATE TABLE ` t2 ` (
` id ` int (11) the DEFAULT NULL, 
` class ` int (11) the DEFAULT NULL, 
The KEY ` id ` (` id `) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1

The data is:

 select * from t2. 
+ -- -- -- -- -- - + -- -- -- -- -- -- -- + 
| | id class | 
+ -- -- -- -- -- - + -- -- -- -- -- -- -- + 
| | 1 | 
| 2 | 2 | 
| | | 10 10 
+ -- -- -- -- -- - + -- -- -- -- -- -- -- +

Transaction 1:

 select * from t2 where id> 4 and id<5 for update;

Transaction 2

 select * from t2 where id=2 for update; Normal 
Select * from t2 where id=10 for update; Block

Is the locking range is (2, 10], this conforms to the next - the key lock,
But

 insert into t2 values (2, 2); Blocking 
Insert into t2 values (10, 10); Normal

Just the opposite and the select for update, this is what causes?
Insert the lock is intention index does not exist, check the gap before the end of the insert lock, but under the condition of existence, is how to check?
And why the mysql will expand the gap to the scope of the index values before and after? And added after a row index, the index value which is next to the key lock, this design is for the sake of what?

And some attempt on the personal home page, welcome criticism directions:
http://wangyoubin.com/? P=105