pnowojski commented on a change in pull request #6367: [FLINK-9850] Add a
string to the print method to identify output for DataStream
URL: https://github.com/apache/flink/pull/6367#discussion_r209237840
##########
File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/sink/PrintSinkFunction.java
##########
@@ -70,15 +83,29 @@ public void open(Configuration parameters) throws
Exception {
// get the target stream
stream = target == STD_OUT ? System.out : System.err;
+ /**
+ * Four possible format options:
+ * sinkId:taskId> output <- sink id provided, parallelism
> 1
+ * sinkId> output <- sink id provided, parallelism
== 1
+ * taskId> output <- no sink id provided,
parallelism > 1
+ * output <- no sink id provided,
parallelism == 1
+ */
+
// set the prefix if we have a >1 parallelism
prefix = (context.getNumberOfParallelSubtasks() > 1) ?
((context.getIndexOfThisSubtask() + 1) + "> ")
: null;
+
+ if (prefix == null) {
Review comment:
Don't use nulls here. In this case we can easily use empty string for the
same purpose and it will be safer (no possible NPE).
Btw, rephrasing this logic like that:
```
completedPrefix = sinkIdentifier;
if (context.getNumberOfParallelSubtasks() > 1)) {
if (!completedPrefix.isEmpty()) {
completedPrefix += ":";
}
completedPrefix += (context.getIndexOfThisSubtask() + 1);
}
if (!completedPrefix.isEmpty()) {
completedPrefix += ">";
}
```
(optionally with ternary operator instead of some 'if' statements - that's
only a matter of taste) simplifies the logic and deduplicate some of the
code/constants.
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