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https://issues.apache.org/jira/browse/FLINK-7475?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16309365#comment-16309365
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ASF GitHub Bot commented on FLINK-7475:
---------------------------------------
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.
> support update() in ListState
> -----------------------------
>
> Key: FLINK-7475
> URL: https://issues.apache.org/jira/browse/FLINK-7475
> Project: Flink
> Issue Type: Improvement
> Components: Core, DataStream API, State Backends, Checkpointing
> Affects Versions: 1.4.0
> Reporter: yf
> Assignee: Bowen Li
> Fix For: 1.5.0
>
>
> If I want to update the list.
> I have to do two steps:
> listState.clear()
> for (Element e : myList) {
> listState.add(e);
> }
> Why not I update the state by:
> listState.update(myList) ?
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