MySQL，使用小于或等于锁定整个表？

Question

当我使用c1<=4或甚至c1<4 OR c1=4时，事务A锁定整个表。 但如果我只使用其中一个，它就不会发生。这是为什么？ “下一把钥匙锁”发生了什么？

DROP TABLE IF EXISTS t1;
CREATE TABLE t1(c1 INT AUTO_INCREMENT, PRIMARY KEY(c1));
INSERT INTO t1 (c1) VALUES (1),(5),(10);

# Transaction A and B starts at the same time

#teste 1
A does, SELECT * FROM t1 WHERE c1<=4 FOR UPDATE;
B does, SELECT * FROM t1 WHERE c1=10 FOR UPDATE; # blocked!

#teste 2
A does, SELECT * FROM t1 WHERE c1<4 FOR UPDATE;
B does, SELECT * FROM t1 WHERE c1=10 FOR UPDATE; # worked!

#teste 3
A does, SELECT * FROM t1 WHERE c1=4 FOR UPDATE;
B does, SELECT * FROM t1 WHERE c1=10 FOR UPDATE; # worked!