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https://issues.apache.org/jira/browse/FLINK-5031?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16100255#comment-16100255
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Aljoscha Krettek commented on FLINK-5031:
-----------------------------------------
In that case, I would suggest to create an {{OutputTag}} for every combination
of tags in your values that you're interested in. Say {{OutputTag("a")}} would
receive elements that have {"tag1, "tag2"} and {{OutputTag("b")}} would receive
elements with tags {{"tag3", "tag5"}}. Inside the {{ProcessFunction}} you do
the filtering based on the element tag and emit to the correct output tags.
This is even more efficient than split/select because split/select creates more
objects under the hood.
Also, the output type of your {{ProcessFunction}} can be {{Void}}, in case you
never need the output.
> Consecutive DataStream.split() ignored
> --------------------------------------
>
> Key: FLINK-5031
> URL: https://issues.apache.org/jira/browse/FLINK-5031
> Project: Flink
> Issue Type: Bug
> Components: DataStream API
> Affects Versions: 1.2.0, 1.1.3
> Reporter: Fabian Hueske
> Assignee: Renkai Ge
>
> The output of the following program
> {code}
> static final class ThresholdSelector implements OutputSelector<Long> {
> long threshold;
> public ThresholdSelector(long threshold) {
> this.threshold = threshold;
> }
> @Override
> public Iterable<String> select(Long value) {
> if (value < threshold) {
> return Collections.singletonList("Less");
> } else {
> return Collections.singletonList("GreaterEqual");
> }
> }
> }
> public static void main(String[] args) throws Exception {
> StreamExecutionEnvironment env =
> StreamExecutionEnvironment.getExecutionEnvironment();
> env.setParallelism(1);
> SplitStream<Long> split1 = env.generateSequence(1, 11)
> .split(new ThresholdSelector(6));
> // stream11 should be [1,2,3,4,5]
> DataStream<Long> stream11 = split1.select("Less");
> SplitStream<Long> split2 = stream11
> // .map(new MapFunction<Long, Long>() {
> // @Override
> // public Long map(Long value) throws Exception {
> // return value;
> // }
> // })
> .split(new ThresholdSelector(3));
> DataStream<Long> stream21 = split2.select("Less");
> // stream21 should be [1,2]
> stream21.print();
> env.execute();
> }
> {code}
> should be {{1, 2}}, however it is {{1, 2, 3, 4, 5}}. It seems that the second
> {{split}} operation is ignored.
> The program is correctly evaluate if the identity {{MapFunction}} is added to
> the program.
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