Github user srowen commented on the pull request:
https://github.com/apache/spark/pull/266#issuecomment-39646924
@pwendell As I saw it, the reason it was used was for the ability to access
the internal `byte[]` buffer directly rather than a copy. However in 2 of 3
cases, it ended up copying anyway (the call to `trim()`). The third case was in
`Serializer.scala`, in `SerializerInstance.serializeMany`. But even there, I
think the copying of the `byte[]` is offset by the fact that it can be merely
`wrap()`ed by a `ByteBuffer` and avoids `ByteBuffer.allocate()` -- another copy
in disguise. From my read, that was the potential difference, and I don't think
there ends up being a meaningful difference. I can't say I'm 100% certain, but
feel pretty sure.
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