Github user kayousterhout commented on a diff in the pull request:
https://github.com/apache/spark/pull/12060#discussion_r60856008
--- Diff: core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
---
@@ -403,32 +403,47 @@ class DAGScheduler(
parents.toList
}
- /** Find ancestor shuffle dependencies that are not registered in
shuffleToMapStage yet */
- private def getAncestorShuffleDependencies(rdd: RDD[_]):
Stack[ShuffleDependency[_, _, _]] = {
- val parents = new Stack[ShuffleDependency[_, _, _]]
+ /**
+ * Find ancestor shuffle dependencies that are not registered in
shuffleToMapStage yet.
+ * This is done in topological order to create ancestor stages first to
ensure that the result
+ * stage graph is correctly built.
+ */
+ private def getAncestorShuffleDependencies(rdd: RDD[_]):
Seq[ShuffleDependency[_, _, _]] = {
+ val parents = new ArrayBuffer[ShuffleDependency[_, _, _]]
val visited = new HashSet[RDD[_]]
// We are manually maintaining a stack here to prevent
StackOverflowError
// caused by recursively visiting
val waitingForVisit = new Stack[RDD[_]]
def visit(r: RDD[_]) {
- if (!visited(r)) {
- visited += r
- for (dep <- r.dependencies) {
- dep match {
- case shufDep: ShuffleDependency[_, _, _] =>
- if (!shuffleToMapStage.contains(shufDep.shuffleId)) {
- parents.push(shufDep)
- }
- case _ =>
+ if (visited(r)) {
--- End diff --
Can this correctness fix be moved into its own pull request / JIRA (and
write a clear description of the correctness problem in the JIRA)? That way it
will be more clearly documented, which makes it easier to avoid re-introducing
the bug in the future (and I don't understand yet what the correctness problem
is). I can review it quickly to avoid further delay!
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