Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/2768#discussion_r86987689
--- Diff:
flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBSimpleState.java
---
@@ -0,0 +1,99 @@
+/*
+ * 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.state.SimpleStateDescriptor;
+import org.apache.flink.api.common.state.State;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.memory.DataInputViewStreamWrapper;
+import org.apache.flink.util.Preconditions;
+import org.rocksdb.ColumnFamilyHandle;
+import org.rocksdb.RocksDBException;
+import org.rocksdb.WriteOptions;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+
+/**
+ * The implementation that stores simple states in RocksDB.
+ *
+ * @param <K> The type of the key.
+ * @param <N> The type of the namespace.
+ * @param <V> The type of value that the state state stores.
+ */
+public class RocksDBSimpleState<K, N, V> extends AbstractRocksDBState<K,
N> implements State<V> {
+
+ /** State descriptor from which to create this state instance */
+ protected final SimpleStateDescriptor<V, ? extends State<V>> stateDesc;
+
+ /** Serializer for the values */
+ protected final TypeSerializer<V> valueSerializer;
+
+ /**
+ * We disable writes to the write-ahead-log here. We can't have these
in the base class
+ * because JNI segfaults for some reason if they are.
+ */
+ protected final WriteOptions writeOptions;
+
+ /**
+ * Creates a new {@code RocksDBSimpleState}.
+ *
+ * @param namespaceSerializer The serializer for the namespace.
+ * @param stateDesc The state identifier for the state. This contains
name and can create a default state value.
+ */
+ public RocksDBSimpleState(ColumnFamilyHandle columnFamily,
+ TypeSerializer<N> namespaceSerializer,
+ SimpleStateDescriptor<V, ? extends State<V>> stateDesc,
+ RocksDBKeyedStateBackend<K> backend
+ ) {
+ super(columnFamily, namespaceSerializer, backend);
+
+ this.stateDesc = Preconditions.checkNotNull(stateDesc, "State
Descriptor");
+ this.valueSerializer = stateDesc.getSerializer();
+
+ writeOptions = new WriteOptions();
+ writeOptions.setDisableWAL(true);
+ }
+
+ @Override
+ public V get() {
+ try {
+ writeCurrentKeyWithGroupAndNamespace();
+ byte[] key = keySerializationStream.toByteArray();
+ byte[] valueBytes = backend.db.get(columnFamily, key);
+ if (valueBytes == null) {
+ return stateDesc.getDefaultValue();
+ }
+ return valueSerializer.deserialize(new
DataInputViewStreamWrapper(new ByteArrayInputStream(valueBytes)));
--- End diff --
Given that this is used only in single threaded settings, we should try to
reuse the `DataInputViewStreamWrapper` and `ByteArrayInputStream`.
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