flink-core/src/main/java/org/apache/flink/types/RowKind.java

/*
 * 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.types;

import org.apache.flink.annotation.PublicEvolving;

/**
 * Lists all kinds of changes that a row can describe in a changelog.
 */
@PublicEvolving
public enum RowKind {

	// Note: Enums have no stable hash code across different JVMs, use toByteValue() for
	// this purpose.

	/**
	 * Insertion operation.
	 */
	INSERT("+I", (byte) 0),

	/**
	 * Update operation with the previous content of the updated row.
	 *
	 * <p>This kind SHOULD occur together with {@link #UPDATE_AFTER} for modelling an update that needs
	 * to retract the previous row first. It is useful in cases of a non-idempotent update, i.e., an
	 * update of a row that is not uniquely identifiable by a key.
	 */
	UPDATE_BEFORE("-U", (byte) 1),

	/**
	 * Update operation with new content of the updated row.
	 *
	 * <p>This kind CAN occur together with {@link #UPDATE_BEFORE} for modelling an update that
	 * needs to retract the previous row first. OR it describes an idempotent update, i.e., an update
	 * of a row that is uniquely identifiable by a key.
	 */
	UPDATE_AFTER("+U", (byte) 2),

	/**
	 * Deletion operation.
	 */
	DELETE("-D", (byte) 3);

	private final String shortString;

	private final byte value;

	/**
	 * Creates a {@link RowKind} enum with the given short string and byte value representation of
	 * the {@link RowKind}.
	 */
	RowKind(String shortString, byte value) {
		this.shortString = shortString;
		this.value = value;
	}

	/**
	 * Returns a short string representation of this {@link RowKind}.
	 *
	 * <p><ul>
	 *     <li>"+I" represents {@link #INSERT}.</li>
	 *     <li>"-U" represents {@link #UPDATE_BEFORE}.</li>
	 *     <li>"+U" represents {@link #UPDATE_AFTER}.</li>
	 *     <li>"-D" represents {@link #DELETE}.</li>
	 * </ul>
	 */
	public String shortString() {
		return shortString;
	}

	/**
	 * Returns the byte value representation of this {@link RowKind}. The byte value is used
	 * for serialization and deserialization.
	 *
	 * <p><ul>
	 * 	 <li>"0" represents {@link #INSERT}.</li>
	 * 	 <li>"1" represents {@link #UPDATE_BEFORE}.</li>
	 * 	 <li>"2" represents {@link #UPDATE_AFTER}.</li>
	 * 	 <li>"3" represents {@link #DELETE}.</li>
	 * </ul>
	 */
	public byte toByteValue() {
		return value;
	}

	/**
	 * Creates a {@link RowKind} from the given byte value. Each {@link RowKind} has a byte
	 * value representation.
	 *
	 * @see #toByteValue() for mapping of byte value and {@link RowKind}.
	 */
	public static RowKind fromByteValue(byte value) {
		switch (value) {
			case 0: return INSERT;
			case 1: return UPDATE_BEFORE;
			case 2: return UPDATE_AFTER;
			case 3: return DELETE;
			default: throw new UnsupportedOperationException(
				"Unsupported byte value '" + value + "' for row kind.");
		}
	}
}