MySQL insert into select锁表的问题（上）

在MySQL中使用insert into table1 select * from table2时，会对table2进行加锁，这个加锁分三种情况：

确认实验条件：

select @@global.tx_isolation,@@session.tx_isolation;

查询结果如下：

@@global.tx_isolation	@@session.tx_isolation
REPEATABLE-READ	REPEATABLE-READ

REPEATABLE-READ是MySQL默认的事务隔离级别

一、后面不带查询条件，不带排序方式insert into table1 select * from table2：

1、直接执行该SQL，使用show engine innodb status;查询锁情况如下

①

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31480, ACTIVE 5 sec inserting

mysql tables in use 2, locked 2

36 lock struct(s), heap size 3520, 1041 row lock(s), undo log entries 1008

②

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31480, ACTIVE 12 sec inserting

mysql tables in use 2, locked 2

856 lock struct(s), heap size 90320, 27223 row lock(s), undo log entries 26370

2、结论：此时MySQL是逐行加锁。

二、查询使用主键排序，insert into table1 select * from table2 order by id：

1、直接执行该SQL，使用show engine innodb status;查询锁情况如下

①

LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31520, ACTIVE 2 sec inserting

mysql tables in use 2, locked 2

21 lock struct(s), heap size 1136, 561 row lock(s), undo log entries 543
②

LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31520, ACTIVE 11 sec inserting

mysql tables in use 2, locked 2

591 lock struct(s), heap size 57552, 18780 row lock(s), undo log entries 18191

2、结论：使用主键排序时，MySQL逐行加锁。

三、使用非主键排序insert into table1 select * from table2 order by modified_date：

1、直接执行该SQL，使用show engine innodb status;查询锁情况如下

①LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31540, ACTIVE 2 sec inserting

mysql tables in use 2, locked 2

1013 lock struct(s), heap size 90320, 32254 row lock(s), undo log entries 564

②

LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31540, ACTIVE 11 sec inserting

mysql tables in use 2, locked 2

1013 lock struct(s), heap size 90320, 32254 row lock(s), undo log entries 16148

③

LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31540, ACTIVE 20 sec inserting

mysql tables in use 2, locked 2

1013 lock struct(s), heap size 90320, 32254 row lock(s), undo log entries 26747  

2、结论：使用非主键排序时，MySQL锁整个表。 

四、在查询条件中使用非主键筛选条件，insert into table1 select * from table2 where modified_date>='2017-10-01 00:00:00'

1、执行该SQL，使用show engine innodb status;查询锁状况

①

LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31564, ACTIVE 1 sec inserting

mysql tables in use 2, locked 2

15 lock struct(s), heap size 1136, 386 row lock(s), undo log entries 374

②

LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 281833671682712, not started

0 lock struct(s), heap size 1136, 0 row lock(s)

---TRANSACTION 31564, ACTIVE 9 sec inserting

mysql tables in use 2, locked 2

548 lock struct(s), heap size 57552, 17381 row lock(s), undo log entries 16836

2、结论：使用非主键筛选条件时，MySQL逐行加锁。