title: Need apache Phoenix UDFs guide
body: <p>I am new to apache phoenix.we need to write phoenix udfs. But I have found very limited documentation on it: on the blog :
  <a href="http://phoenix-hbase.blogspot.in/2013/04/how-to-add-your-own-built-in-function.html" rel="nofollow">http://phoenix-hbase.blogspot.in/2013/04/how-to-add-your-own-built-in-function.html</a>
  Above link just gives very simple function which has only single i/p and o/p type.
  I am searching since a week but could not find any document explaining how to write evaluate function which takes multiple parameters and can return different datatypes based on inputs. All I have currently is understanding phoenix source code of built in functions.which is cumbersome.Is there any comprehensive documentation of Phoenix UDFs.</p>