Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3712#discussion_r132141831
  
    --- Diff: 
flink-connectors/flink-jdbc/src/main/java/org/apache/flink/api/java/io/jdbc/JDBCAppendTableSink.java
 ---
    @@ -0,0 +1,97 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.flink.api.java.io.jdbc;
    +
    +import org.apache.flink.annotation.VisibleForTesting;
    +import org.apache.flink.api.common.typeinfo.TypeInformation;
    +import org.apache.flink.api.java.DataSet;
    +import org.apache.flink.api.java.typeutils.RowTypeInfo;
    +import org.apache.flink.streaming.api.datastream.DataStream;
    +import org.apache.flink.table.sinks.AppendStreamTableSink;
    +import org.apache.flink.table.sinks.BatchTableSink;
    +import org.apache.flink.table.sinks.TableSink;
    +import org.apache.flink.types.Row;
    +import org.apache.flink.util.Preconditions;
    +
    +/**
    + * An at-least-once Table sink for JDBC.
    + *
    + * <p>The mechanisms of Flink guarantees delivering messages at-least-once 
to this sink.
    + * However, one common use case is to run idempotent queries (e.g., 
<code>REPLACE</code> or
    + * <code>INSERT OVERWRITE</code>) to upsert into the database and achieve 
exactly-once semantic.</p>
    + */
    +public class JDBCAppendTableSink implements AppendStreamTableSink<Row>, 
BatchTableSink<Row> {
    +   private final JDBCSinkFunction sink;
    +
    +   private String[] fieldNames;
    +   private TypeInformation[] fieldTypes;
    +
    +   JDBCAppendTableSink(JDBCOutputFormat outputFormat) {
    +           this.sink = new JDBCSinkFunction(outputFormat);
    +   }
    +
    +   public static JDBCAppendTableSinkBuilder builder() {
    +           return new JDBCAppendTableSinkBuilder();
    +   }
    +
    +   @Override
    +   public void emitDataStream(DataStream<Row> dataStream) {
    +           dataStream.addSink(sink);
    +   }
    +
    +   @Override
    +   public void emitDataSet(DataSet<Row> dataSet) {
    +           dataSet.output(sink.outputFormat);
    +   }
    +
    +   @Override
    +   public TypeInformation<Row> getOutputType() {
    +           return new RowTypeInfo(fieldTypes, fieldNames);
    +   }
    +
    +   @Override
    +   public String[] getFieldNames() {
    +           return fieldNames;
    +   }
    +
    +   @Override
    +   public TypeInformation<?>[] getFieldTypes() {
    +           return fieldTypes;
    +   }
    +
    +   @Override
    +   public TableSink<Row> configure(String[] fieldNames, 
TypeInformation<?>[] fieldTypes) {
    +           int[] types = sink.outputFormat.getTypesArray();
    +           Preconditions.checkArgument(fieldTypes.length == types.length);
    +           for (int i = 0; i < types.length; ++i) {
    +                   
Preconditions.checkArgument(JDBCTypeUtil.typeInformationToSqlType(fieldTypes[i])
 == types[i],
    --- End diff --
    
    add more details to error message like: `"Schema of output table 
incompatible with JDBCAppendTableSink: expected [type1, type2, type3, ...], 
actual [type1, type2]"`


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