[GitHub] flink pull request #4963: [FLINK-7475] [core][DataStream API] support update...

[StefanRRichter <gi...@git.apache.org>]

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

    https://github.com/apache/flink/pull/4963#discussion_r159386188
  
    --- Diff: flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/util/MergeUtils.java ---
    @@ -0,0 +1,63 @@
    +/*
    + * 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.contrib.streaming.state.util;
    +
    +import org.apache.flink.annotation.VisibleForTesting;
    +
    +import java.util.List;
    +
    +/**
    + * Utils to simulate StringAppendTestOperator's merge operations in RocksDB.
    + */
    +public class MergeUtils {
    +	@VisibleForTesting
    +	protected static final byte DELIMITER = ',';
    +
    +	/**
    +	 * Merge operands into a single value that can be put directly into RocksDB.
    +	 */
    +	public static byte[] merge(List<byte[]> operands) {
    +		if (operands == null) {
    +			return null;
    +		}
    +
    +		if (operands.size() < 2) {
    +			return operands.get(0);
    --- End diff --
    
    This will fail if size == 0.


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