Github user rmetzger commented on the pull request:
https://github.com/apache/flink/pull/301#issuecomment-71178244
Hadoops `FileOutputFormat` has the following method
```java
public static String getUniqueName(JobConf conf, String name) {
int partition = conf.getInt(JobContext.TASK_PARTITION, -1);
if (partition == -1) {
throw new IllegalArgumentException(
"This method can only be called from within a Job");
}
String taskType = (conf.getBoolean(JobContext.TASK_ISMAP, true)) ? "m"
: "r";
NumberFormat numberFormat = NumberFormat.getInstance();
numberFormat.setMinimumIntegerDigits(5);
numberFormat.setGroupingUsed(false);
return name + "-" + taskType + "-" + numberFormat.format(partition);
}
```
So users have to overwrite the method if they want to use a custom filename.
I'll remove the configuration-based approach.
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