echauchot commented on a change in pull request #11055: [BEAM-9436] Improve GBK
in spark structured streaming runner
URL: https://github.com/apache/beam/pull/11055#discussion_r397246846
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File path:
runners/spark/src/main/java/org/apache/beam/runners/spark/structuredstreaming/translation/batch/functions/GroupAlsoByWindowViaOutputBufferFn.java
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@@ -65,9 +65,15 @@ public GroupAlsoByWindowViaOutputBufferFn(
@Override
public Iterator<WindowedValue<KV<K, Iterable<InputT>>>> call(
- KV<K, Iterable<WindowedValue<InputT>>> kv) throws Exception {
- K key = kv.getKey();
- Iterable<WindowedValue<InputT>> values = kv.getValue();
+ K key, Iterator<WindowedValue<KV<K, InputT>>> iterator) throws Exception
{
+
+ // we have to meterialize the Iterator because
ReduceFnRunner.processElements expects
+ // ArrayList<WindowedValue<InputT>> and not Iterator<WindowedValue<KV<K,
InputT>>>
Review comment:
I have already taken a look. Each ReduceFnRunner instance works in parallel
in the parallel groups of the flatmapGroups and works on a materialization of
the elements of the group. See among other things ReduceFnRunner line 326:
reduceFnRunner collects all the windows to merge them. Changing the signature
of the processElement method will not change the need for materialization. The
important is to avoid materializing the whole collection in one place (which we
do not do). We materialize only the part of the collection for each group.
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