MYSQL事务级别：http://blog.itpub.net/29254281/viewspace-1398273/ (可重复读)
http://blog.csdn.net/chen77716/article/details/6742128#t2 (MVCC)
深入理解Apache的mod_rewrite(htaccess) http://www.yeeyan.org/articles/view/jcky/59298
apache官网关于 rewrite的讲解： http://httpd.apache.org/docs/trunk/rewrite/