Github user chiwanpark commented on a diff in the pull request: https://github.com/apache/flink/pull/1585#discussion_r52098334 --- Diff: flink-java/src/main/java/org/apache/flink/api/java/operators/SortPartitionOperator.java --- @@ -79,16 +112,33 @@ public SortPartitionOperator(DataSet<T> dataSet, String sortField, Order sortOrd * local partition sorting of the DataSet. * * @param field The field expression referring to the field of the additional sort order of - * the local partition sorting. - * @param order The order of the additional sort order of the local partition sorting. + * the local partition sorting. + * @param order The order of the additional sort order of the local partition sorting. * @return The DataSet with sorted local partitions. */ public SortPartitionOperator<T> sortPartition(String field, Order order) { + if (useKeySelector) { + throw new InvalidProgramException("Expression keys cannot be appended after selector function keys"); + } + int[] flatOrderKeys = getFlatFields(field); this.appendSorting(flatOrderKeys, order); return this; } + /** + * Appends an additional sort order with the specified field in the specified order to the + * local partition sorting of the DataSet. + * + * @param keyExtractor The KeySelector function which extracts the key value of the additional + * sort order of the local partition sorting. + * @param order The order of the additional sort order of the local partition sorting. + * @return The DataSet with sorted local partitions. + */ + public <K> SortPartitionOperator<T> sortPartition(KeySelector<T, K> keyExtractor, Order order) { --- End diff -- If we remove this method, the following code can be executed: ```java DataSet<MyObject> data = ... DataSet<MyObject> result = data .sortPartition(new KeySelector<MyObject, Integer> { public Integer getKey(MyObject value) throws Exception { return value.myInt; } }, Order.ASCENDING) .sortPartition(new KeySelector<MyObject, String> { public String getKey(MyObject value) throws Exception { return value.myString; } }, Order.ASCENDING); ``` In above case, `data` is sorted twice (first by Integer, second by String) and the result of first sorting will be ignored. I think this is quite confusing for users.
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