Github user rxin commented on the pull request:
https://github.com/apache/spark/pull/860#issuecomment-45015385
I don't think there would be any perf issues with this, but might be good
to do a perf run to see if there are any perf penalty.
There are possibly two perf downsides: 1. contention on lazy val's lock,
and 2 the extra branch. However, I think in this case the iterator is consumed
by a single thread, so the JVM can get rid of the lock, and branch prediction
should work well for the extra branch ...
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