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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (BEAM-3247) Sample.any memory constraint
Date Mon, 27 Nov 2017 22:52:01 GMT


ASF GitHub Bot commented on BEAM-3247:

jkff commented on a change in pull request #4175: [BEAM-3247] fix Sample.any performance

 File path: sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/
 @@ -209,29 +202,67 @@ public void populateDisplayData(DisplayData.Builder builder) {
-   * A {@link DoFn} that returns up to limit elements from the side input PCollection.
+   * A {@link DoFn} that outputs up to limit elements.
-  private static class SampleAnyDoFn<T> extends DoFn<Void, T> {
-    long limit;
-    final PCollectionView<Iterable<T>> iterableView;
+  private static class SampleAnyDoFn<T> extends DoFn<T, T> {
 Review comment:
   Oh sorry, I looked in the wrong place in the code. Yeah, this implementation is wrong:
the main element (null in this case) is in the global window, so of course it's not allowed
to access a side input that is windowed non-globally, because it's ambiguous which window
should be accessed. It plays even more poorly with triggering. See
. All the more reason to fix this!

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> Sample.any memory constraint
> ----------------------------
>                 Key: BEAM-3247
>                 URL:
>             Project: Beam
>          Issue Type: Improvement
>          Components: sdk-java-core
>    Affects Versions: 2.1.0
>            Reporter: Neville Li
>            Assignee: Neville Li
>            Priority: Minor
> Right now {{Sample.any}} converts the collection to an iterable view and take first n
in a side input. This may require materializing the entire collection to disk and is potentially
> It can be fixed by applying a truncating `DoFn` first, then a combine into `List<T>`
which limits the list size, and finally flattening the list.

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