hudi-common/src/main/java/org/apache/hudi/common/model/HoodieRecordMerger.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
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 */

package org.apache.hudi.common.model;

import org.apache.avro.Schema;
import org.apache.hudi.ApiMaturityLevel;
import org.apache.hudi.PublicAPIClass;
import org.apache.hudi.common.config.TypedProperties;
import org.apache.hudi.common.model.HoodieRecord.HoodieRecordType;
import org.apache.hudi.common.util.Option;
import org.apache.hudi.common.util.collection.Pair;

import java.io.IOException;
import java.io.Serializable;

/**
 * HoodieMerge defines how to merge two records. It is a stateless component.
 * It can implement the merging logic of HoodieRecord of different engines
 * and avoid the performance consumption caused by the serialization/deserialization of Avro payload.
 */
@PublicAPIClass(maturity = ApiMaturityLevel.EVOLVING)
public interface HoodieRecordMerger extends Serializable {

  String DEFAULT_MERGER_STRATEGY_UUID = "eeb8d96f-b1e4-49fd-bbf8-28ac514178e5";

  /**
   * This method converges combineAndGetUpdateValue and precombine from HoodiePayload.
   * It'd be associative operation: f(a, f(b, c)) = f(f(a, b), c) (which we can translate as having 3 versions A, B, C
   * of the single record, both orders of operations applications have to yield the same result)
   */
  Option<Pair<HoodieRecord, Schema>> merge(HoodieRecord older, Schema oldSchema, HoodieRecord newer, Schema newSchema, TypedProperties props) throws IOException;

  /**
   * The record type handled by the current merger.
   * SPARK, AVRO, FLINK
   */
  HoodieRecordType getRecordType();

  /**
   * The kind of merging strategy this recordMerger belongs to. An UUID represents merging strategy.
   */
  String getMergingStrategy();
}