奇龍在做db變更的時候，update被阻塞：

[email protected] : (none) 23:51:35> show variables like ‘%ignore_builtin%’;

| Variable_name | Value |

| ignore_builtin_innodb | OFF |

—>檢視show processlist:

| 5696061853 | houyi | 10.242.219.1:42661 | dbname | Query | 22936 | Sending data | select * from xx_shot where id in (select parent_xx_shot from xx_shot where parent_xx_shot!=”” a |

|5696162576 | houyi | 10.242.219.1:44290 | dbname | Query | 22695 | Sending data | select id from xx_shot where id in (select parent_xx_shot from xx_shot where parent_xx_shot!=”” |

| 5696208999 | houyi | 10.242.219.1:45610 | dbname | Query | 22586 | Sending data | select id from xx_shot where id in (select parent_xx_shot from xx_shot where parent_xx_shot

—>檢視show innodb status\G;

mysql tables in use 2, locked 14562 lock struct(s), heap size 489456, 604071 row lock(s)MySQL thread id 5696208999, query id 15226780028 10.242.219.1 houyi Sending dataselect id from xx_shot where id in (select parent_xx_shot from xx_shot where parent_xx_shot!=”” and gmt_create>’2012-04-27′ and xx_shot_progress<0 )Trx read view will not see trx with id >= 1 2411988144, sees < 1 2411827879—TRANSACTION 1 2411935441, ACTIVE 22560 sec, process no 1982, OS thread id 1188837696 fetching rows, thread declared inside InnoDB 228mysql tables in use 2, locked 15311 lock struct(s), heap size 636912, 1199769 row lock(s)

這個表確實被鎖住了

—>kill 子查詢

kill 5696061853 ;

kil 5696162576;

kil 5696208999;

[email protected] : dbname 23:41:40> update xx_shot set xx_shot_progress=-6 where id=2083430;

Query OK, 1 row affected (0.00 sec)Rows matched: 1 Changed: 1 Warnings: [email protected] : dbname 23:41:42> commit;

Query OK, 0 rows affected (0.00 sec)
測試5.1 innodb db [email protected] 02:51:27>show global variables like ‘%igno%’; Variable_name | Value |

ignore_builtin_innodb | ON |

[email protected] 02:51:53>show global variables like ‘%version%’;

| Variable_name | Value |

| innodb_version | 1.0.9 |

session1：

[email protected] 02:46:31>select id from xx_shot where id in (select parent_xx_shot   from xx_shot where parent_xx_shot != “” and gmt_create > ‘2012-04-27’  and xx_shot_progress < 0 group by device_id HAVING count(device_id) = 1);

session2：

[email protected] 02:47:26>update xx_shot set xx_shot_progress=-6 where id=1163184;Query OK, 0 rows affected (0.00 sec)

關閉掉bultin，innodb_version為1.0.9中子查詢並沒有阻塞更新；
造成上面問題的還有一個主要原因為mysql處理子查詢的不優秀：http://hidba.org/?p=412

[email protected] 03:21:06>explain select id  from xx_shot c1, (select parent_xx_shot-> from xx_shot where parent_xx_shot != “” and gmt_create  ‘2012-04-27’  and xx_shot_progress < 0  group by device_id  HAVING count(device_id) = 1) c2  where c1.id = c2.parent_xx_shot  ;

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

| 1 | PRIMARY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE noticed after reading const tables |

| 2 | DERIVED | xx_shot | ALL | NULL | NULL | NULL | NULL | 170786 | Using where; Using temporary; Using filesort |

改寫sql後：[email protected] 03:21:06>explain select id  from xx_shot c1,  (select parent_xx_shot  from xx_shot where parent_xx_shot != “”  and gmt_create > ‘2012-04-27’ and xx_shot_progress < 0 group by device_id HAVING count(device_id) = 1) c2 where c1.id = c2.parent_xx_shot ;

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

| 1 | PRIMARY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE noticed after reading const tables |

| 2 | DERIVED | xx_shot | ALL | NULL | NULL | NULL | NULL | 170786 | Using where; Using temporary; Using filesort |

執行時間：[email protected] 03:21:05>select id  from xx_shot c1,  (select parent_xx_shot  from xx_shot where parent_xx_shot != “”  and gmt_create > ‘2012-04-27’ and xx_shot_progress < 0 group by device_id HAVING count(device_id) = 1) c2 where c1.id = c2.parent_xx_shot ;

Empty set (0.17 sec)