<pre name="code" class="html">mysql> show variables like '%tx_isolation%';
+---------------+-----------------+
| Variable_name | Value |
+---------------+-----------------+
| tx_isolation | REPEATABLE-READ |
+---------------+-----------------+
1 row in set (0.00 sec)
Session 1:
mysql> show index from test;
Empty set (0.00 sec)
mysql> update test set name='xxxx' where id=2;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
Session 2:
mysql> select * from test;
+------+------+
| id | name |
+------+------+
| 1 | b |
| 11 | aa |
| 2 | xxxx |
| 10 | a |
+------+------+
4 rows in set (0.00 sec)
mysql> update test set name='xxxx' where id=10;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
没有索引的情况 ,RR隔离级别 是锁全表
//*********************************************************************
Session 1:
mysql> update test set id=99 where id=1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
Session 2:
mysql> update test set id=100 where id=2; --HANG
//测试有主键的情况下:
mysql> CREATE TABLE `s100` (
-> `sn` int(11) NOT NULL AUTO_INCREMENT,
-> `id` int,
-> `info` varchar(40) DEFAULT NULL,
-> PRIMARY KEY (`sn`)
-> ) ENGINE=InnoDB AUTO_INCREMENT=225 DEFAULT CHARSET=utf8 ;
Query OK, 0 rows affected (0.04 sec)
mysql> show index from s100;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| s100 | 0 | PRIMARY | 1 | sn | A | 0 | NULL | NULL | | BTREE | | |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
1 row in set (0.00 sec)
Session 1：
mysql> update s100 set id=100 where id=1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
Session 2:
mysql> update s100 set id=200 where id=2;---Hang
//测试更新是否锁全表:
mysql> explain update Product set
-> status = '3'
-> where status = '2' and buyToTime < '2016-05-10 12:54:00';
+----+-------------+---------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------+-------+---------------+---------+---------+------+------+-------------+
| 1 | SIMPLE | Product | index | NULL | PRIMARY | 4 | NULL | 506 | Using where |
+----+-------------+---------+-------+---------------+---------+---------+------+------+-------------+
1 row in set (0.00 sec)
从possible_keys中所选择使用的索引
正常走索引的更新是:
mysql> explain update test set id=100 where id=1;
+----+-------------+-------+-------+---------------+-----------+---------+-------+------+------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+---------------+-----------+---------+-------+------+------------------------------+
| 1 | SIMPLE | test | range | test_idx1 | test_idx1 | 5 | const | 1 | Using where; Using temporary |
+----+-------------+-------+-------+---------------+-----------+---------+-------+------+------------------------------+
1 row in set (0.00 sec)