My contribution to Python UDFs in Pig has finally released as part of the new and shiny 0.8 release! I’ve been meaning to blog about how this came about when I had time, but Dmitriy saved me the work, so I’ll just quote him instead:
This is the outcome of PIG-928; it was quite a pleasure to watch this develop over time — while most Pig tickets wind up getting worked on by at most one or two people, this turned into a collaboration of quite a few developers, many of them new to the project — Kishore Gopalakrishna’s patch was the initial conversation starter, which was then hacked on or merged into similar work by Woody Anderson, Arnab Nandi, Julien Le Dem, Ashutosh Chauhan and Aniket Mokashi (Aniket deserves an extra shout-out for patiently working to incorporate everyone’s feedback and pushing the patch through the last mile).
Yay Open Source! Documentation is available on the Pig website, but here’s a one-line example of what you can now do:
register 'test.py' using jython as myfuncs;
Notice that we’re using a python script instead of a jar. All python functions in test.py become available as UDFs to Pig!
Going forward, there are two things I didn’t get to do, which I’d love any of my dear readers to pick up on. First, we’re still not at par with SCOPE’s ease-of-use since UDFs can’t be inlined yet (a la BaconSnake). This is currently open as a separate Apache JIRA issue, would be great to see patches here!
The second feature that I really wanted to make part of this patch submission, and didn’t have time for, was Java source UDF support as a JaninoScriptEngine. Currently, Pig users have to bundle their UDF code as jars, which quickly becomes painful. The goal of the
ScriptEngine architecture is to let multiple languages be implemented and plugged in, so I really hope someone takes the time to look at the Janino project, which will allow Java source UDFs with zero performance penalty. This would also make it the first dynamically compiled query system over Hadoop (as far as I know), and opens up a world of query optimization work to explore.