Flink 自定义GroupConcat函数

函数实现逻辑

import org.apache.flink.table.api.DataTypes;
import org.apache.flink.table.api.dataview.ListView;
import org.apache.flink.table.runtime.functions.aggregate.BuiltInAggregateFunction;
import org.apache.flink.table.types.DataType;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Objects;

public class GroupConcatFullUDF extends BuiltInAggregateFunction<String, GroupConcatFullUDF.GroupConcatAccumulator> {
   
   

    private static final String DEFAULT_SEPARATOR = ",";

    @Override
    public DataType getOutputDataType() {
   
   
        return DataTypes.STRING();
    }

    @Override
    public List<DataType> getArgumentDataTypes() {
   
   
        List<DataType> types = new ArrayList<>(3);
        types.add(DataTypes.STRING());
        types.add(DataTypes.STRING());
        types.add(DataTypes.BOOLEAN());
        return types;
    }

    @Override
    public DataType getAccumulatorDataType() {
   
   
        return DataTypes.STRUCTURED(
                GroupConcatUDF.GroupConcatAccumulator.class,
                DataTypes.FIELD(
                        "list",
                        ListView.newListViewDataType(
                                DataTypes.STRING())),
                DataTypes.FIELD(
                        "retractList",
                        ListView.newListViewDataType(
                                DataTypes.STRING())));
    }

    public void resetAccumulator(GroupConcatUDF.GroupConcatAccumulator acc) {
   
   
        acc.list.clear();
        acc.retractList.clear();
    }

    @Override
    public GroupConcatAccumulator createAccumulator() {