I tested hex in a 1000w times for loop with random numbers，
old hex avg time cost is 4.92 s，optimize hex avg time cost is 0.46 s which faster nearly 10x.
replace is an user defined function, which is to replace all old substrings with a new substring in a string, as follow:
mysql> select replace("http://www.baidu.com:9090", "9090", "");
+------------------------------------------------------+
| replace('http://www.baidu.com:9090', '9090', '') |
+------------------------------------------------------+
| http://www.baidu.com: |
+------------------------------------------------------+
