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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.dinky.shaded.paimon.mergetree.compact;

import org.dinky.shaded.paimon.KeyValue;

import javax.annotation.Nullable;

/**
 * Merge function to merge multiple {@link KeyValue}s.
 *
 * IMPORTANT, Object reusing inside the kv of the {@link #add} input:
 *
 * 

 *   Please don't save KeyValue and InternalRow references to the List: the KeyValue of the
 *       first two objects and the InternalRow object inside them are safe, but the reference of the
 *       third object may overwrite the reference of the first object.
 *   
You can save fields references: fields don't reuse their objects.
 * 
 *
 * @param  result type
 */
public interface MergeFunction {

    /** Reset the merge function to its default state. */
    void reset();

    /** Add the given {@link KeyValue} to the merge function. */
    void add(KeyValue kv);

    /** Get current merged value. Return null if this merged result should be skipped. */
    @Nullable
    T getResult();
}