/*
 * 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.lucene.index;

import java.io.IOException;

/**
 * This is a {@link LogMergePolicy} that measures size of a segment as the number of documents (not
 * taking deletions into account).
 */
public class LogDocMergePolicy extends LogMergePolicy {

  /** Default minimum segment size. @see setMinMergeDocs */
  public static final int DEFAULT_MIN_MERGE_DOCS = 1000;

  /** Sole constructor, setting all settings to their defaults. */
  public LogDocMergePolicy() {
    minMergeSize = DEFAULT_MIN_MERGE_DOCS;

    // maxMergeSize(ForForcedMerge) are never used by LogDocMergePolicy; set
    // it to Long.MAX_VALUE to disable it
    maxMergeSize = Long.MAX_VALUE;
    maxMergeSizeForForcedMerge = Long.MAX_VALUE;
  }

  @Override
  protected long size(SegmentCommitInfo info, MergeContext mergeContext) throws IOException {
    return sizeDocs(info, mergeContext);
  }

  /**
   * Sets the minimum size for the lowest level segments. Any segments below this size are
   * candidates for full-flush merges and merged more aggressively in order to avoid having a long
   * tail of small segments. Large values of this parameter increase the merging cost during
   * indexing if you flush small segments.
   */
  public void setMinMergeDocs(int minMergeDocs) {
    minMergeSize = minMergeDocs;
  }

  /**
   * Get the minimum size for a segment to remain un-merged.
   *
   * @see #setMinMergeDocs *
   */
  public int getMinMergeDocs() {
    return (int) minMergeSize;
  }
}
