Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/11242#discussion_r57014360
--- Diff: core/src/main/scala/org/apache/spark/rdd/UnionRDD.scala ---
@@ -62,7 +64,23 @@ class UnionRDD[T: ClassTag](
var rdds: Seq[RDD[T]])
extends RDD[T](sc, Nil) { // Nil since we implement getDependencies
+ // Evaluate partitions in parallel. Partitions of each rdd will be
cached by the `partitions`
+ // val in `RDD`.
+ private[spark] lazy val parallelPartitionEval: Boolean = {
--- End diff --
> I thought the issue here was use for reading/writing data rather than
getSplits
The issue is introducing concurrent calls to getSplits.
[PARQUET-16|https://issues.apache.org/jira/browse/PARQUET-16] is a suggestion
to cache the results of file system operations during split planning, which
would have to be done by a cache shared across instances. (Instead, we fixed
the underlying problem with HADOOP-12810.)
> if this is a problem, this doesn't resolve it. More immediately, there
are cases where the same instance of InputFormat is accessed concurrently.
If this is true, then your line of reasoning makes sense. Where are
InputFormat instances accessed concurrently?
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