Hello all, I am working with Hive 0.12 right now on YARN. When I am writing a table that is admittedly quite "wide" (there are lots of columns, near 60, including one binary field that can get quite large). Some tasks will fail on ORC file write with Java Heap Space Issues.
I have confirmed that using RCFiles on the same data produces no failures. This led me down the path of experimenting with the table properties. Obviously, living on the cutting edge here makes it so there is not tons of documentation on what these settings do, I have lots of slide shows showing me the settings that be used to tune ORC, but not what they do, or what the ramifications may be. For example, I've gone ahead and reduced the orc.compress.size to 64k This seems to address lots of the failures, (all other things being unchanged). But what does that mean for me in the long run? Larger files? More files? How is this negatively affecting me from a file perspective? In addition, would this be a good time to try SNAPPY over ZLIB as my default compression? I tried to find some direct memory comparisons but didn't see anything. So, give my data and the issues on write for my wide table, how would you recommend I address this? Is the compress.size the way to go? What are the long term affects of this? Any thoughts would be welcome. Thanks! John
