Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1553#discussion_r54386465
--- 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());
+
toCombiner.setShipStrategy(ShipStrategyType.FORWARD,
DataExchangeMode.PIPELINED);
+ GroupReduceNode combinerNode =
((GroupReduceNode) node).getCombinerUtilityNode();
+
combinerNode.setParallelism(in.getSource().getParallelism());
+
if(toCombiner.getSource().getInputs().iterator().hasNext()) {
+ Channel source =
toCombiner.getSource().getInputs().iterator().next();
+ // A combiner plan node is created with
the map as the input
+ SingleInputPlanNode combiner = new
SingleInputPlanNode(combinerNode, "Combine("+node.getOperator()
+ .getName()+")", source,
DriverStrategy.SORTED_GROUP_COMBINE);
+ addCombinerNodeData(in, toCombiner,
combiner);
+ Channel combinerChannel = new
Channel(combiner);
+
combinerChannel.setShipStrategy(ShipStrategyType.FORWARD,
DataExchangeMode.PIPELINED);
--- End diff --
If we have:
`[Some-Op] --(a)-partition--> [Partition-Op] --(b)-fwd--> [Reduce-Op]`
then `in` is the `--(b)-fwd-->` channel and `node` is the the
`[Reduce-Op]`.
The combine operator should be inserted like this:
`[Some-Op] --(1)-fwd--> [Combine-Op] --(2)-partition--> [Partition-Op]
--(3)-fwd--> [Reduce-Op]`
- The channel (1) must be a new forward/pipelined channel.
- The channel (2) must be new channel with the same shipping and exchange
strategies as channel (a).
- The channel (3) should be the original channel (b) which is the `in`
parameter.
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