Github user mxm commented on a diff in the pull request:
https://github.com/apache/flink/pull/999#discussion_r36508794
--- 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 --
I'm not sure if it is good practice to ignore `null` referenced streams.
Why not let it fail here? We might hide other errors by skipping the
problematic stream here.
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