Github user pwendell commented on a diff in the pull request:
https://github.com/apache/spark/pull/1165#discussion_r14801587
--- Diff: core/src/main/scala/org/apache/spark/storage/MemoryStore.scala ---
@@ -141,6 +174,86 @@ private class MemoryStore(blockManager: BlockManager,
maxMemory: Long)
}
/**
+ * Unfold the given block in memory safely.
+ *
+ * The safety of this operation refers to avoiding potential OOM
exceptions caused by
+ * unfolding the entirety of the block in memory at once. This is
achieved by periodically
+ * checking whether the memory restrictions for unfolding blocks are
still satisfied,
+ * stopping immediately if not. This check is a safeguard against the
scenario in which
+ * there is not enough free memory to accommodate the entirety of a
single block.
+ *
+ * This method returns either a fully unfolded array or a partially
unfolded iterator.
+ */
+ def unfoldSafely(
--- End diff --
Could this use a proper type parameter (e.g. `Iterator[T]`) instead of
using `Any`? If we need to cast the result to a more general `Iterator[Any]`
for putting it in the block manager that's fine. We should try to use as
specific a type as possible in each case (currently the code takes the result
of this and casts `Iterator[Any]` to `Iteratory[T]` which is scary).
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