reduce a data stream to other type

[Soheil Pourbafrani]

Hi, I have a keyed datastream in the type of Tuple2<Long, byte[]>. I want to reduce it and merge all of the byte[] for a key. (the first filed (Long) is the key). So I need reduce function return the type Tuple2<Long, ArrayList<byte[]>>, but reduce function didn't allow that! How can I do such job in Flink?

[Hequn Cheng]

Hi Soheil,

Yes, reduce function doesn't allow this. A ReduceFunction specifies how two elements from the input are combined to produce an output element of the same type. 

You can use AggregateFunction or FoldFunction. More details here[1].

Best, Hequn

[1] https://ci.apache.org/projects/flink/flink-docs-master/dev/stream/operators/windows.html#window-functions

On Sat, Jul 14, 2018 at 9:24 PM, Soheil Pourbafrani <[hidden email]> wrote:

Hi, I have a keyed datastream in the type of Tuple2<Long, byte[]>. I want to reduce it and merge all of the byte[] for a key. (the first filed (Long) is the key). So I need reduce function return the type Tuple2<Long, ArrayList<byte[]>>, but reduce function didn't allow that! How can I do such job in Flink?