[GitHub] aljoscha commented on a change in pull request #7496: [FLINK-11323] Upgrade KryoSerializer snapshot to implement new TypeSerializerSnapshot interface

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aljoscha commented on a change in pull request #7496: [FLINK-11323] Upgrade KryoSerializer snapshot to implement new TypeSerializerSnapshot interface
URL: https://github.com/apache/flink/pull/7496#discussion_r258032514
 
 

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 File path: flink-core/src/main/java/org/apache/flink/api/java/typeutils/runtime/kryo/OptionalMap.java
 ##########
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+/*
+ * 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.typeutils.runtime.kryo;
+
+import org.apache.flink.annotation.VisibleForTesting;
+
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.Map.Entry;
+import java.util.Optional;
+import java.util.Set;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import javax.annotation.Nullable;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * An OptionalMap is an order preserving map (like {@link LinkedHashMap}) where keys have a unique string name, but are
+ * optionally present, and the values are optional.
+ */
+final class OptionalMap<K, V> {
+
+
+	// --------------------------------------------------------------------------------------------------------
+	// Factory
+	// --------------------------------------------------------------------------------------------------------
+
+	/**
+	 * Creates an {@code OptionalMap} from the provided map.
+	 *
+	 * <p>This method is the equivalent of {@link Optional#of(Object)} but for maps. To support more than one {@code NULL}
+	 * key, an optional map requires a unique string name to be associated with each key (provided by keyNameGetter)
+	 *
+	 * @param sourceMap     a source map to wrap as an optional map.
+	 * @param keyNameGetter function that assigns a unique name to the keys of the source map.
+	 * @param <K>           key type
+	 * @param <V>           value type
+	 * @return an {@code OptionalMap} with optional named keys, and optional values.
+	 */
+	static <K, V> OptionalMap<K, V> optionalMapOf(LinkedHashMap<K, V> sourceMap, Function<K, String> keyNameGetter) {
+
+		LinkedHashMap<String, KeyValue<K, V>> underlyingMap = new LinkedHashMap<>(sourceMap.size());
+
+		sourceMap.forEach((k, v) -> {
+			String keyName = keyNameGetter.apply(k);
+			underlyingMap.put(keyName, new KeyValue<>(k, v));
+		});
+
+		return new OptionalMap<>(underlyingMap);
+	}
+
+	/**
+	 * Tries to merges the keys and the values of @right into @left.
+	 */
+	static <K, V> MergeResult<K, V> mergeRightIntoLeft(OptionalMap<K, V> left, OptionalMap<K, V> right) {
+		OptionalMap<K, V> merged = new OptionalMap<>(left);
+		merged.putAll(right);
+
+		return new MergeResult<>(merged, isLeftPrefixOfRight(left, right));
+	}
+
+	// --------------------------------------------------------------------------------------------------------
+	// Constructor
+	// --------------------------------------------------------------------------------------------------------
+
+	private final LinkedHashMap<String, KeyValue<K, V>> underlyingMap;
+
+	OptionalMap() {
+		this(new LinkedHashMap<>());
+	}
+
+	@SuppressWarnings("CopyConstructorMissesField")
+	OptionalMap(OptionalMap<K, V> optionalMap) {
+		this(new LinkedHashMap<>(optionalMap.underlyingMap));
+	}
+
+	private OptionalMap(LinkedHashMap<String, KeyValue<K, V>> underlyingMap) {
+		this.underlyingMap = checkNotNull(underlyingMap);
+	}
+
+	// --------------------------------------------------------------------------------------------------------
+	// API
+	// --------------------------------------------------------------------------------------------------------
+
+	int size() {
+		return underlyingMap.size();
+	}
+
+	void put(String keyName, @Nullable K key, @Nullable V value) {
+		checkNotNull(keyName);
+
+		underlyingMap.compute(keyName, (unused, kv) ->
+			(kv == null) ? new KeyValue<>(key, value) : kv.merge(key, value));
+	}
+
+	void putAll(OptionalMap<K, V> right) {
+		for (Entry<String, KeyValue<K, V>> entry : right.underlyingMap.entrySet()) {
+			KeyValue<K, V> kv = entry.getValue();
+			this.put(entry.getKey(), kv.key, kv.value);
+		}
+	}
+
+	/**
+	 * returns the key names of any keys or values that are absent.
+	 */
+	Set<String> absentKeysOrValues() {
+		return underlyingMap.entrySet()
+			.stream()
+			.filter(OptionalMap::keyOrValueIsAbsent)
+			.map(Entry::getKey)
+			.collect(Collectors.toSet());
+	}
+
+	/**
+	 * assuming all the entries of this map are present (keys and values) this method would return
+	 * a map with these key and values, striped from their Optional wrappers.
+	 * NOTE: please note that if any of the key or values are absent this method would throw an {@link IllegalStateException}.
+	 */
+	LinkedHashMap<K, V> unwrapOptionals() {
+		final LinkedHashMap<K, V> unwrapped = new LinkedHashMap<>(underlyingMap.size());
+
+		for (Entry<String, KeyValue<K, V>> entry : underlyingMap.entrySet()) {
+			String namedKey = entry.getKey();
+			KeyValue<K, V> kv = entry.getValue();
+			if (kv.key == null) {
+				throw new IllegalStateException("Missing key '" + namedKey + "'");
+			}
+			if (kv.value == null) {
+				throw new IllegalStateException("Missing value for the key '" + namedKey + "'");
+			}
+			unwrapped.put(kv.key, kv.value);
+		}
+
+		return unwrapped;
+	}
+
+	/**
+	 * returns the key names added to this map.
 
 Review comment:
   Nitpick: lowercase `returns` -> `Returns`

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