About epoll and select the difference between:
1, epoll and select all I / O multiplexing technology, can monitor multiple real-time I / state events O 2, epoll higher efficiency than select, mainly based on its operating system supports I / O, event notification mechanism, and select is based on a polling mechanism 3, select can support parallel I / O is relatively small, and can not be modified
From innodb index structure analysis, why the index key length can not be too long?
key too long can result in a number of key page which can be stored decreases, and indirectly led to
the number of pages indexed tree increases, increase the index level, thus affecting the overall efficiency of queries change
rate.