習慣了oracle數據庫的select for update nowait的同學，如果轉在mysql環境開發的話，也許會不太適應——目前builtin版本的innodb不支持nowait句法的。早在08年已經被作為bug提了出來（http://bugs.mysql.com/bug.php?id=36285）。還好innodb plugin1.0.2開始支持bug文章里提及的session級innodb_lock_wait_timeout控制（http://dev.mysql.com/doc/innodb-plugin/1.0/en/innodb-other-changes-innodb_lock_wait_timeout.html） Before InnoDB Plugin 1.0.2, the only way to set this parameter was in the MySQL option file (my.cnf or my.ini), and changing it required shutting down and restarting the server. Beginning with the InnoDB Plugin 1.0.2, the configuration parameter innodb_lock_wait_timeout can be set at runtime with the SET GLOBAL or SET SESSION commands.
該問題的回復 [5 May 17:08] Bugs System Pushed into 5.1.47 (revid:joro@sun.com-20100505145753-ivlt4hclbrjy8eye) (version source revid:vasil.dimov@oracle.com-20100331130613-8ja7n0vh46a80457) (merge vers: 5.1.46) (pib:16)[6 May 16:58] Paul DuBois Push resulted from incorporation of InnoDB tree. No changes pertinent to this bug. Re-closing. 看到該問題也是最終被close掉。值得一提的是目前看到的一些問題都說是5147做fix，mysql51系列啥時候是個頭？？50系列目前主流的是508X系列吧，最近facebook發布了5084的補丁包，而percona則已經發布了5190-b21版本，oracle則磨刀霍霍向55系列。。。
btw，作為對select for update nowait的實現，其實如果數據庫實現不了，其實應用做個超時控制就可以了，把sql執行放到超時控制代碼里，具體情況要看開發語言了。
測試: -- builtin innodb user@test 10:14:37>set innodb_lock_wait_timeout=1; ERROR 1238 (HY000): Variable 'innodb_lock_wait_timeout' is a read only variable
user@sbtest 10:15:54>show variables like 'innodb_lock_wait_timeout'; +--------------------------+-------+ | Variable_name | Value | +--------------------------+-------+ | innodb_lock_wait_timeout | 1 | +--------------------------+-------+ 1 row in set (0.01 sec)
user@sbtest 10:16:02>show global variables like 'innodb_lock_wait_timeout'; +--------------------------+-------+ | Variable_name | Value | +--------------------------+-------+ | innodb_lock_wait_timeout | 15 | +--------------------------+-------+ 1 row in set (0.00 sec)
