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mysqlcasual6-next-key-lock
- 14. MySQLのlock
❖ record lock
❖ 単一のindex recordのロック
❖ e.g.) PRIMARY KEYが1のヤツ
❖ gap lock
❖ index recordの間、先頭、末尾のロック
❖ e.g. 1) PRIMARY KEYが1~3の間のロック
❖ e.g. 2) PRIMARY KEYが3以上のロック
- 16. 勘所
❖ index record lockである
❖ covering indexの場合などはlock範囲が異なる
❖ http://blog.kamipo.net/entry/2013/12/03/235900
❖ クエリによってロック範囲が細かく異なる
❖ MySQLの公式のドキュメントが詳しい
❖ InnoDB 内で各種 SQL ステートメントによって設定されるロック
❖ http://dev.mysql.com/doc/refman/5.1-olh/ja/innodb-locks-set.html
- 18. schema
mysql> CREATE TABLE `mysqlcasual` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`col1` int(11) NOT NULL,
`col2` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`id`),
KEY `idx_col1` (`col1`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
- 19. data
mysql> SELECT * FROM mysqlcasual;
+----+------+------+
| id | col1 | col2 |
+----+------+------+
| 1 | 2 | 0 |
| 2 | 4 | 0 |
| 3 | 6 | 0 |
| 4 | 8 | 0 |
| 5 | 10 | 0 |
| 6 | 12 | 0 |
| 7 | 14 | 0 |
| 8 | 16 | 0 |
+----+------+------+
- 20. WHERE col1 = 6
+-----+------+------+
| id | col1 | col2 |
+-----+------+------+
| 1 | 2 | 0 |
| 2 | 4 | 0 |
| 3 | 6 | 0 |
| 4 | 8 | 0 |
| 5 | 10 | 0 |
| 6 | 12 | 0 |
| 7 | 14 | 0 |
| 8 | 16 | 0 |
+-----+------+------+
- 21. WHERE col1 > 6
+-----+------+------+
| id | col1 | col2 |
+-----+------+------+
| 1 | 2 | 0 |
| 2 | 4 | 0 |
| 3 | 6 | 0 |
|(gap)| (gap)| (gap)|
| 4 | 8 | 0 |
| 5 | 10 | 0 |
| 6 | 12 | 0 |
| 7 | 14 | 0 |
| 8 | 16 | 0 |
|(gap)| (gap)| (gap)|
+-----+------+------+
- 22. WHERE col1 >= 6
+-----+------+------+
| id | col1 | col2 |
+-----+------+------+
| 1 | 2 | 0 |
| 2 | 4 | 0 |
|(gap)| (gap)| (gap)|
| 3 | 6 | 0 |
| 4 | 8 | 0 |
| 5 | 10 | 0 |
| 6 | 12 | 0 |
| 7 | 14 | 0 |
| 8 | 16 | 0 |
|(gap)| (gap)| (gap)|
+-----+------+------+
- 23. WHERE col1 < 6
+-----+------+------+
| id | col1 | col2 |
+-----+------+------+
|(gap)| (gap)| (gap)|
| 1 | 2 | 0 |
| 2 | 4 | 0 |
|(gap)| (gap)| (gap)|
| 3 | 6 | 0 |
| 4 | 8 | 0 |
| 5 | 10 | 0 |
| 6 | 12 | 0 |
| 7 | 14 | 0 |
| 8 | 16 | 0 |
+-----+------+------+
- 24. WHERE col1 <= 6
+-----+------+------+
| id | col1 | col2 |
+-----+------+------+
|(gap)| (gap)| (gap)|
| 1 | 2 | 0 |
| 2 | 4 | 0 |
| 3 | 6 | 0 |
|(gap)| (gap)| (gap)|
| 4 | 8 | 0 |
| 5 | 10 | 0 |
| 6 | 12 | 0 |
| 7 | 14 | 0 |
| 8 | 16 | 0 |
+-----+------+------+