Dawid Wysakowicz created FLINK-18629:
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Summary: ConnectedStreams#keyBy can not derive key TypeInformation for lambda KeySelectors
Key: FLINK-18629
URL:
https://issues.apache.org/jira/browse/FLINK-18629 Project: Flink
Issue Type: Bug
Components: API / DataStream
Affects Versions: 1.11.0, 1.10.0, 1.12.0
Reporter: Dawid Wysakowicz
Assignee: Dawid Wysakowicz
Fix For: 1.10.2, 1.12.0, 1.11.2
Following test fails:
{code}
@Test
public void testKeyedConnectedStreamsType() {
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
DataStreamSource<Integer> stream1 = env.fromElements(1, 2);
DataStreamSource<Integer> stream2 = env.fromElements(1, 2);
ConnectedStreams<Integer, Integer> connectedStreams = stream1.connect(stream2)
.keyBy(v -> v, v -> v);
KeyedStream<?, ?> firstKeyedInput = (KeyedStream<?, ?>) connectedStreams.getFirstInput();
KeyedStream<?, ?> secondKeyedInput = (KeyedStream<?, ?>) connectedStreams.getSecondInput();
assertThat(firstKeyedInput.getKeyType(), equalTo(Types.INT));
assertThat(secondKeyedInput.getKeyType(), equalTo(Types.INT));
}
{code}
The problem is that the wildcard type is evaluated as {{Object}} for lambdas, which in turn produces {{GenericTypeInfo<Object>}} for any KeySelector provided as lambda.
I suggest changing the method signature to:
{code}
public <K1, K2> ConnectedStreams<IN1, IN2> keyBy(
KeySelector<IN1, K1> keySelector1,
KeySelector<IN2, K2> keySelector2)
{code}
This would be a code compatible change. Might break the compatibility of state backend (would change derived key type info). Nevertheless there is a workaround to use:
{code}
public <KEY> ConnectedStreams<IN1, IN2> keyBy(
KeySelector<IN1, KEY> keySelector1,
KeySelector<IN2, KEY> keySelector2,
TypeInformation<KEY> keyType)
{code}
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