Github user mateiz commented on a diff in the pull request:
https://github.com/apache/spark/pull/1165#discussion_r15331347
--- Diff: core/src/main/scala/org/apache/spark/storage/MemoryStore.scala ---
@@ -87,9 +97,47 @@ private class MemoryStore(blockManager: BlockManager,
maxMemory: Long)
values: Iterator[Any],
level: StorageLevel,
returnValues: Boolean): PutResult = {
- val valueEntries = new ArrayBuffer[Any]()
- valueEntries ++= values
- putValues(blockId, valueEntries, level, returnValues)
+ putValues(blockId, values, level, returnValues, allowPersistToDisk =
true)
+ }
+
+ /**
+ * Attempt to put the given block in memory store.
+ *
+ * There may not be enough space to fully unroll the iterator in memory,
in which case we
+ * optionally drop the values to disk if
+ * (1) the block's storage level specifies useDisk, and
+ * (2) `allowPersistToDisk` is true.
+ *
+ * One scenario in which `allowPersistToDisk` is false is when the
BlockManager reads a block
+ * back from disk and attempts to cache it in memory. In this case, we
should not persist the
+ * block back on disk again, as it is already in disk store.
+ */
+ private[storage] def putValues(
--- End diff --
Nit: it's kind of weird that this is called putValues when it takes an
Iterator, and BlockManager has something called putIterator. Maybe this should
also be putIterator.
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