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https://issues.apache.org/jira/browse/FLINK-6114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15935589#comment-15935589
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Luke Hutchison edited comment on FLINK-6114 at 3/22/17 1:05 AM:
----------------------------------------------------------------
I figured maybe I was using distinct() wrong, so I tried replacing the code
around {{// (1)}} with the following, to no avail:
{code}
DataSet<Tuple2<String, Integer>> blank_numKeys =
blank_key_totScore
.groupBy(1)
// (1)
.reduceGroup((it, out) -> {
for (@SuppressWarnings("unused") Tuple3<String, K,
Float> t : it) {
out.collect(new Tuple2<String, Integer>("", 1));
}
}).groupBy(0).sum(1);
{code}
was (Author: lukehutch):
I figured maybe I was using distinct() wrong, so I tried replacing the code
around {{// (1)}} with the following, to no avail:
{code}
DataSet<Tuple2<String, Integer>> blank_numKeys =
blank_key_totScore
.groupBy(1)
// (1)
.reduceGroup((it, out) -> {
for (@SuppressWarnings("unused") Tuple3<String, K,
Float> t : it) {
out.collect(new Tuple2<String, Integer>("", 1));
}
});
{code}
> Type checking fails with generics, even when concrete type of field is not
> needed
> ---------------------------------------------------------------------------------
>
> Key: FLINK-6114
> URL: https://issues.apache.org/jira/browse/FLINK-6114
> Project: Flink
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.2.0
> Reporter: Luke Hutchison
>
> The Flink type checker does not allow generic types to be used in any field
> of a tuple when a join is being executed, even if the generic is not in a
> field that is involved in the join.
> I have a type Tuple3<String, K, Float>, which contains a generic type
> parameter K. I am joining using .where(0).equalTo(0). The type of field 0 is
> well-defined as String. However, this gives me the following error:
> {noformat}
> Exception in thread "main"
> org.apache.flink.api.common.functions.InvalidTypesException: Type of
> TypeVariable 'K' in 'public static org.apache.flink.api.java.DataSet
> mypkg.MyClass.method(params)' could not be determined. This is most likely a
> type erasure problem. The type extraction currently supports types with
> generic variables only in cases where all variables in the return type can be
> deduced from the input type(s).
> at
> org.apache.flink.api.java.typeutils.TypeExtractor.createSubTypesInfo(TypeExtractor.java:989)
> {noformat}
> The code compiles fine, however -- the static type system is able to
> correctly resolve the types in the surrounding code.
> Really only the fields that are affected by joins (or groupBy, aggregation
> etc.) should be checked for concrete types in this way.
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