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From "Till Rohrmann (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-3052) Optimizer does not push properties out of bulk iterations
Date Fri, 20 Nov 2015 11:21:11 GMT
Till Rohrmann created FLINK-3052:
------------------------------------

             Summary: Optimizer does not push properties out of bulk iterations
                 Key: FLINK-3052
                 URL: https://issues.apache.org/jira/browse/FLINK-3052
             Project: Flink
          Issue Type: Bug
          Components: Optimizer
    Affects Versions: 0.10.0
            Reporter: Till Rohrmann
            Assignee: Till Rohrmann
             Fix For: 0.10.1


Flink's optimizer should be able to reuse interesting properties from outside the loop. In
order to do that it is sometimes necessary to append a NoOp node to the step function which
recomputes the required properties.

This is currently not working for {{BulkIterations}}, because the plans with the appended
NoOp nodes are not added to the overall list of candidates.

This not only leads to sub-optimal plan selection but sometimes to the rejection of valid
jobs. The following job, for example, will be falsely rejected by flink.

{code}
ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

		DataSet<Tuple1<Long>> input1 = env.generateSequence(1, 10).map(new MapFunction<Long,
Tuple1<Long>>() {
			@Override
			public Tuple1<Long> map(Long value) throws Exception {
				return new Tuple1<>(value);
			}
		});

		DataSet<Tuple1<Long>> input2 = env.generateSequence(1, 10).map(new MapFunction<Long,
Tuple1<Long>>() {
			@Override
			public Tuple1<Long> map(Long value) throws Exception {
				return new Tuple1<>(value);
			}
		});

		DataSet<Tuple1<Long>> distinctInput = input1.distinct();

		IterativeDataSet<Tuple1<Long>> iteration = distinctInput.iterate(10);

		DataSet<Tuple1<Long>> iterationStep = iteration
				.coGroup(input2)
				.where(0)
				.equalTo(0)
				.with(new CoGroupFunction<Tuple1<Long>, Tuple1<Long>, Tuple1<Long>>()
{
					@Override
					public void coGroup(
							Iterable<Tuple1<Long>> first,
							Iterable<Tuple1<Long>> second,
							Collector<Tuple1<Long>> out) throws Exception {
						Iterator<Tuple1<Long>> it = first.iterator();

						if (it.hasNext()) {
							out.collect(it.next());
						}
					}
				});

		DataSet<Tuple1<Long>> iterationResult = iteration.closeWith(iterationStep);

		iterationResult.output(new DiscardingOutputFormat<Tuple1<Long>>());
{code}



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