The parameter 'part' of parse_url function does not support lower case, and parse protocol not right.
And This function does not support parse 'port'.
This PR tries to make parse_url function case insensitive and support parse 'port'.
The issue: #4451
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: |
+------------------------------------------------------+
