We call Row.copy() in many places throughout SQL but UnsafeRow currently throws UnsupportedOperationException when copy() is called.
Supporting copying when ObjectPool is used may be difficult, since we may need to handle deep-copying of objects in the pool. In addition, this copy() method needs to produce a self-contained row object which may be passed around / buffered by downstream code which does not understand the UnsafeRow format.
In the long run, we'll need to figure out how to handle the ObjectPool corner cases, but this may be unnecessary if other changes are made. Therefore, in order to unblock my sort patch (#6444) I propose that we support copy() for the cases where UnsafeRow does not use an ObjectPool and continue to throw UnsupportedOperationException when an ObjectPool is used.
This patch accomplishes this by modifying UnsafeRow so that it knows the size of the row's backing data in order to be able to copy it into a byte array.
Author: Josh Rosen <joshrosen@databricks.com>
Closes#7306 from JoshRosen/SPARK-8932 and squashes the following commits:
338e6bf [Josh Rosen] Support copy for UnsafeRows that do not use ObjectPools.
b55499a44a