Github user uce commented on a diff in the pull request:
https://github.com/apache/flink/pull/896#discussion_r34503752
--- Diff: flink-java/src/main/java/org/apache/flink/api/java/DataSet.java
---
@@ -408,14 +408,16 @@ public long count() throws Exception {
JobExecutionResult res = getExecutionEnvironment().execute();
ArrayList<byte[]> accResult = res.getAccumulatorResult(id);
- try {
- return
SerializedListAccumulator.deserializeList(accResult, serializer);
- }
- catch (ClassNotFoundException e) {
- throw new RuntimeException("Cannot find type class of
collected data type.", e);
- }
- catch (IOException e) {
- throw new RuntimeException("Serialization error while
deserializing collected data", e);
+ if (accResult != null) {
+ try {
+ return
SerializedListAccumulator.deserializeList(accResult, serializer);
+ } catch (ClassNotFoundException e) {
+ throw new RuntimeException("Cannot find type
class of collected data type.", e);
+ } catch (IOException e) {
+ throw new RuntimeException("Serialization error
while deserializing collected data", e);
+ }
+ } else {
+ throw new RuntimeException("The job result did not
contain any accumulator data.");
--- End diff --
The error message might be confusing to the user, because a user should not
care that the count is implemented with accumulators. Maybe let's make it
explicit in the message that this case is a bug and should not happen.
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