Question

我正在使用配置为使用flink-table jar的本地Flink 1.6群集（这意味着我程序的jar不包含flink-table）。使用以下代码

import org.apache.flink.api.common.typeinfo.TypeHint;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.operators.DataSource;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.api.java.typeutils.ResultTypeQueryable;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.TableEnvironment;
import org.apache.flink.table.api.java.BatchTableEnvironment;
import org.apache.flink.table.functions.AggregateFunction;
import org.apache.flink.types.Row;

import java.util.ArrayList;
import java.util.List;

public class JMain {
    public static void main(String[] args) throws Exception {
        ExecutionEnvironment execEnv = ExecutionEnvironment.getExecutionEnvironment();
        BatchTableEnvironment tableEnv = TableEnvironment.getTableEnvironment(execEnv);

        tableEnv.registerFunction("enlist", new Enlister());

        DataSource<Tuple2<String, String>> source = execEnv.fromElements(
                new Tuple2<>("a", "1"),
                new Tuple2<>("a", "2"),
                new Tuple2<>("b", "3")
        );

        Table table = tableEnv.fromDataSet(source, "a, b")
                .groupBy("a")
                .select("enlist(a, b)");

        tableEnv.toDataSet(table, Row.class)
                .print();
    }

    public static class Enlister
            extends AggregateFunction<List<String>, ArrayList<String>>
            implements ResultTypeQueryable<List<String>>
    {
        @Override
        public ArrayList<String> createAccumulator() {
            return new ArrayList<>();
        }

        @Override
        public List<String> getValue(ArrayList<String> acc) {
            return acc;
        }

        @SuppressWarnings("unused")
        public void accumulate(ArrayList<String> acc, String a, String b) {
            acc.add(a + ":" + b);
        }

        @SuppressWarnings("unused")
        public void merge(ArrayList<String> acc, Iterable<ArrayList<String>> it) {
            for (ArrayList<String> otherAcc : it) {
                acc.addAll(otherAcc);
            }
        }

        @SuppressWarnings("unused")
        public void resetAccumulator(ArrayList<String> acc) {
            acc.clear();
        }

        @Override
        public TypeInformation<List<String>> getProducedType() {
            return TypeInformation.of(new TypeHint<List<String>>(){});
        }
    }
}

我得到这个奇怪的例外：

org.apache.flink.table.api.ValidationException: Expression Enlister(List('a, 'b)) failed on input check: Given parameters do not match any signature. 
Actual: (java.lang.String, java.lang.String) 
Expected: (java.lang.String, java.lang.String)

但是，如果我不实施ResultTypeQueryable，我得到了预期的输出：

Starting execution of program
[b:3]
[a:1, a:2]
Program execution finished
Job with JobID 20497bd3efe44fab0092a05a8eb7d9de has finished.
Job Runtime: 270 ms
Accumulator Results: 
- 56e0e5a9466b84ae44431c9c4b7aad71 (java.util.ArrayList) [2 elements]

我的实际用例似乎需要ResultTypeQueryable，因为否则我会收到此异常：

The return type of function ... 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

有什么办法可以解决这个问题？

Answer 1

我试图在一个小程序中重现该问题，但我做不到，它只会在我的较大项目中发生。不幸的是，覆盖getResultType()和getAccumulatorType()都没有帮助，在这种情况下，我遇到了这个异常：

java.lang.IndexOutOfBoundsException
    at org.apache.flink.api.java.typeutils.TupleTypeInfoBase.getTypeAt(TupleTypeInfoBase.java:199)
    at org.apache.flink.api.java.typeutils.RowTypeInfo.getTypeAt(RowTypeInfo.java:179)
    at org.apache.flink.api.common.operators.Keys$ExpressionKeys.isSortKey(Keys.java:444)
    at org.apache.flink.api.java.operators.SortPartitionOperator.ensureSortableKey(SortPartitionOperator.java:150)
    at org.apache.flink.api.java.operators.SortPartitionOperator.<init>(SortPartitionOperator.java:75)
    at org.apache.flink.api.java.DataSet.sortPartition(DataSet.java:1414)

即使没有覆盖，我实际上也有该异常。唯一对我有用的是：

String[] fieldNames = new String[] {
        "result"
};
TypeInformation<?>[] types = new TypeInformation[] {
        TypeInformation.of(new TypeHint<List<String>>(){})
};

tableEnv.toDataSet(table, Types.ROW(fieldNames, types))...

使用Table AggregateFunction和ResultTypeQueryable时的ValidationException

1 个答案: