Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/3801#discussion_r114320148
--- Diff:
flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateHandle.java
---
@@ -0,0 +1,209 @@
+/*
+ * 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;
+
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.runtime.state.CompositeStateHandle;
+import org.apache.flink.runtime.state.KeyGroupRange;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.SharedStateHandle;
+import org.apache.flink.runtime.state.SharedStateRegistry;
+import org.apache.flink.runtime.state.StateUtil;
+import org.apache.flink.runtime.state.StreamStateHandle;
+import org.apache.flink.util.Preconditions;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * The handle to states in incremental snapshots taken by {@link
RocksDBKeyedStateBackend}
+ */
+public class RocksDBKeyedStateHandle implements KeyedStateHandle,
CompositeStateHandle {
+
+ private static final Logger LOG =
LoggerFactory.getLogger(RocksDBKeyedStateHandle.class);
+
+ private static final long serialVersionUID = -8328808513197388231L;
+
+ private final JobID jobId;
+
+ private final String operatorIdentifier;
+
+ private final KeyGroupRange keyGroupRange;
+
+ private final Set<String> newSstFileNames;
--- End diff --
Overall, I wonder how this class impacts larger deployments, where a lot of
those state handles are send via RPC. I suggest to keep the serialization
footprint as small as possible. For example, maybe we can eliminate
`newSstFileNames` by introducing two `Map<String, StreamStateHandle>`:
`newSstFiles` and `previousSstFiles`, instead of checking against a set. This
could even simplify some methods, e.g. the registration or deletion code. We
could then provide a method that delivers an combined iterator over all
`Entry<String, StreamStateHandle>`from both maps.
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