Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/15248#discussion_r81126007
--- Diff:
core/src/main/scala/org/apache/spark/deploy/history/HistoryServer.scala ---
@@ -179,7 +180,11 @@ class HistoryServer(
}
--- End diff --
OK, let me ask a different question -- when would you ever want to call
getApplicationInfoList, given this problem? the other usages seem to just pick
out a single element, so it's wasteful for the same reason. It just seems weird
to have two methods for this.
The existing method already only promises an Iterator which seems like the
right thing to do. The problem is that it gets there by materializing a whole
collection. Why is that unavoidable -- you can map() an iterator's elements
without any evaluation of its elements or needing to first materialize the
collection.
That's why I think getApplicationInfo is really what needs to change to
provide something else like an Iterator, and that ends up being pretty easy --
FsHistoryProvider just has to give an iterator over applications.
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