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https://issues.apache.org/jira/browse/FLINK-2495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14679126#comment-14679126
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ASF GitHub Bot commented on FLINK-2495:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/999#discussion_r36587360
--- Diff:
flink-staging/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/datastream/DataStream.java
---
@@ -256,9 +256,11 @@ public ExecutionConfig getExecutionConfig() {
DataStream<OUT> returnStream = this.copy();
for (DataStream<OUT> stream : streams) {
- for (DataStream<OUT> ds : stream.unionedStreams) {
- validateUnion(ds.getId());
- returnStream.unionedStreams.add(ds.copy());
+ if (stream != null) {
--- End diff --
Right there will be an error, but the error is helpful because it indicates
a problem with the user program.
If the union is silently ignored, the program might behave differently from
what the user expects and produce invalid results.
I would argue, that a `union(null)` is never intended and should be be
brought to the user's attention. Also, this error might reveal more problems of
the user program.
> Add a null point check in API DataStream.union
> ----------------------------------------------
>
> Key: FLINK-2495
> URL: https://issues.apache.org/jira/browse/FLINK-2495
> Project: Flink
> Issue Type: Bug
> Components: Streaming
> Affects Versions: 0.10
> Reporter: Huang Wei
> Fix For: 0.10
>
> Original Estimate: 168h
> Remaining Estimate: 168h
>
> The API(public DataStream<OUT> union(DataStream<OUT>... streams)) is a
> external interface for user.
> The parameter "streams" maybe null and it will throw NullPointerException
> error.
> This test below can be intuitive to explain this problem:
> package org.apache.flink.streaming.api;
> import org.apache.flink.api.common.functions.MapFunction;
> import org.apache.flink.streaming.api.datastream.DataStream;
> import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
> import
> org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction;
> import org.junit.Test;
> /**
> * Created by HuangWHWHW on 2015/8/7.
> */
> public class test {
> public static class sourceFunction extends
> RichParallelSourceFunction<String> {
> public sourceFunction() {
> }
> @Override
> public void run(SourceContext<String> sourceContext) throws
> Exception {
> sourceContext.collect("a");
> }
> @Override
> public void cancel() {
> }
> }
> @Test
> public void testUnion(){
> StreamExecutionEnvironment env =
> StreamExecutionEnvironment.getExecutionEnvironment();
> env.setParallelism(1);
> DataStream<String> source = env.addSource(new sourceFunction());
> DataStream<String> temp1 = null;
> DataStream<String> temp2 = source.map(new MapFunction<String,
> String>() {
> @Override
> public String map(String value) throws Exception {
> if (value == "a") {
> return "This is for test temp2.";
> }
> return null;
> }
> });
> DataStream<String> sink = temp2.union(temp1);
> sink.print();
> try {
> env.execute();
> }catch (Exception e){
> e.printStackTrace();
> }
> }
> }
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