We just had Stefan over on the user@drill list stick with us through thick and thin to get a very simple UDF up. He isn't a dolt by any means, but here is his signature on email describing his state of mind:
Regards, > -Stefan (*not the happiest camper*) The only reason that this guy is still with us is that Jim Bates exchanged quite a number of emails. The clear reason that he had problems is lack of documentation and thus understanding of how to write a UDF. The current state of affairs is that it is unnecessarily hard to contribute to Drill. This is clearly having a deleterious effect on building the community of contributors. We need to fix this. There is a place on the web site that describes how to write a UDF, but it is clearly failing to explain the big picture of what is happening and it doesn't highlight the fact that you aren't really writing Java code when writing a Drill UDF, but instead are using Java to write in a more limited language. Stefan's recent experience should be a perfect opportunity to improve this documentation by describing the process better.
