Luke Hutchison created FLINK-6276:
-------------------------------------
Summary: InvalidTypesException: Unknown Error. Type is null.
Key: FLINK-6276
URL: https://issues.apache.org/jira/browse/FLINK-6276
Project: Flink
Issue Type: Bug
Components: Core, DataSet API
Affects Versions: 1.2.0
Reporter: Luke Hutchison
Quite frequently when writing Flink code, I get the exception
{{InvalidTypesException: Unknown Error. Type is null.}}
A small example that triggers it is:
{code}
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.util.Collector;
public class TestMain {
@SafeVarargs
public static <K, V> DataSet<Tuple2<K, List<V>>> join(V
missingValuePlaceholder,
DataSet<Tuple2<K, V>>... datasets) {
DataSet<Tuple2<K, List<V>>> join = null;
for (int i = 0; i < datasets.length; i++) {
final int datasetIdx = i;
if (datasetIdx == 0) {
join = datasets[datasetIdx] //
.map(t -> new Tuple2<>(t.f0, Arrays.asList(t.f1))) //
.name("start join");
} else {
join = join.coGroup(datasets[datasetIdx]) //
.where(0).equalTo(0) //
.with((Iterable<Tuple2<K, List<V>>> li,
Iterable<Tuple2<K, V>> ri,
Collector<Tuple2<K, List<V>>> out) -> {
K key = null;
List<V> vals = new ArrayList<>(datasetIdx + 1);
Iterator<Tuple2<K, List<V>>> lIter = li.iterator();
if (!lIter.hasNext()) {
for (int j = 0; j < datasetIdx; j++) {
vals.add(missingValuePlaceholder);
}
} else {
Tuple2<K, List<V>> lt = lIter.next();
key = lt.f0;
vals.addAll(lt.f1);
if (lIter.hasNext()) {
throw new RuntimeException("Got non-unique
key: " + key);
}
}
Iterator<Tuple2<K, V>> rIter = ri.iterator();
if (!rIter.hasNext()) {
vals.add(missingValuePlaceholder);
} else {
Tuple2<K, V> rt = rIter.next();
key = rt.f0;
vals.add(rt.f1);
if (rIter.hasNext()) {
throw new RuntimeException("Got non-unique
key: " + key);
}
}
out.collect(new Tuple2<K, List<V>>(key, vals));
}) //
.name("join #" + datasetIdx);
}
}
return join;
}
public static void main(String[] args) throws Exception {
ExecutionEnvironment env =
ExecutionEnvironment.getExecutionEnvironment();
DataSet<Tuple2<String, Integer>> x = //
env.fromElements(new Tuple2<>("a", 3), new Tuple2<>("b", 4),
new Tuple2<>("c", 5));
DataSet<Tuple2<String, Integer>> y = //
env.fromElements(new Tuple2<>("b", 0), new Tuple2<>("c", 1),
new Tuple2<>("d", 2));
DataSet<Tuple2<String, Integer>> z = //
env.fromElements(new Tuple2<>("c", 7), new Tuple2<>("d", 8),
new Tuple2<>("e", 9));
System.out.println(join(-1, x, y, z).collect());
}
}
{code}
The stacktrace that is triggered is:
{noformat}
Exception in thread "main"
org.apache.flink.api.common.functions.InvalidTypesException: The return type of
function 'join(TestMain.java:23)' could not be determined automatically, due to
type erasure. You can give type information hints by using the returns(...)
method on the result of the transformation call, or by letting your function
implement the 'ResultTypeQueryable' interface.
at org.apache.flink.api.java.DataSet.getType(DataSet.java:174)
at
org.apache.flink.api.java.operators.CoGroupOperator$CoGroupOperatorSets.where(CoGroupOperator.java:424)
at
com.rentlogic.buildingscores.flink.experimental.TestMain.join(TestMain.java:27)
at
com.rentlogic.buildingscores.flink.experimental.TestMain.main(TestMain.java:74)
Caused by: org.apache.flink.api.common.functions.InvalidTypesException: Input
mismatch: Unknown Error. Type is null.
at
org.apache.flink.api.java.typeutils.TypeExtractor.validateInputType(TypeExtractor.java:1134)
at
org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:409)
at
org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:349)
at
org.apache.flink.api.java.typeutils.TypeExtractor.getMapReturnTypes(TypeExtractor.java:164)
at org.apache.flink.api.java.DataSet.map(DataSet.java:215)
at
com.rentlogic.buildingscores.flink.experimental.TestMain.join(TestMain.java:23)
... 1 more
Caused by: org.apache.flink.api.common.functions.InvalidTypesException: Unknown
Error. Type is null.
at
org.apache.flink.api.java.typeutils.TypeExtractor.validateInfo(TypeExtractor.java:1161)
at
org.apache.flink.api.java.typeutils.TypeExtractor.validateInfo(TypeExtractor.java:1234)
at
org.apache.flink.api.java.typeutils.TypeExtractor.validateInputType(TypeExtractor.java:1131)
... 6 more
{noformat}
The code compiles fine, and typechecks. Maybe something is wrong with the code;
but either way, Flink should report a better error message.
A separate issue here is that the error message is being reported for the wrong
function: the problem is not with the return type of {{ join(TestMain.java:23)
}}, it is some internal type (probably for a lambda or something) within the
function. (It is the {{where}} clause that throws the exception.)
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