Github user fhueske commented on a diff in the pull request: https://github.com/apache/flink/pull/1553#discussion_r53152430 --- Diff: flink-optimizer/src/main/java/org/apache/flink/optimizer/operators/GroupReduceWithCombineProperties.java --- @@ -87,19 +92,39 @@ public DriverStrategy getStrategy() { return DriverStrategy.SORTED_GROUP_REDUCE; } - @Override public SingleInputPlanNode instantiate(Channel in, SingleInputNode node) { if (in.getShipStrategy() == ShipStrategyType.FORWARD) { // adjust a sort (changes grouping, so it must be for this driver to combining sort - if (in.getLocalStrategy() == LocalStrategy.SORT) { - if (!in.getLocalStrategyKeys().isValidUnorderedPrefix(this.keys)) { - throw new RuntimeException("Bug: Inconsistent sort for group strategy."); + if(in.getSource().getOptimizerNode() instanceof PartitionNode) { + // Inject a combiner before the partition node + Channel toCombiner = new Channel(in.getSource()); --- End diff -- This channel is also not used in the plan. It is just used for look-ups.
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