/*
 * 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 LogMergePolicy that measures size of a segment as the total byte size of the segment's files. /** This is a {@link LogMergePolicy} that measures size of a
 *  segment as the total byte size of the segment's files. */
public class LogByteSizeMergePolicy extends LogMergePolicy {

  
Default minimum segment size.  @see setMinMergeMB /** Default minimum segment size.  @see setMinMergeMB */
  public static final double DEFAULT_MIN_MERGE_MB = 1.6;

  
Default maximum segment size.  A segment of this size
 or larger will never be merged.  @see setMaxMergeMB /** Default maximum segment size.  A segment of this size
   *  or larger will never be merged.  @see setMaxMergeMB */
  public static final double DEFAULT_MAX_MERGE_MB = 2048;

  
Default maximum segment size.  A segment of this size
 or larger will never be merged during forceMerge.  @see setMaxMergeMBForForceMerge /** Default maximum segment size.  A segment of this size
   *  or larger will never be merged during forceMerge.  @see setMaxMergeMBForForceMerge */
  public static final double DEFAULT_MAX_MERGE_MB_FOR_FORCED_MERGE = Long.MAX_VALUE;

  
Sole constructor, setting all settings to their
 defaults. /** Sole constructor, setting all settings to their
   *  defaults. */
  public LogByteSizeMergePolicy() {
    minMergeSize = (long) (DEFAULT_MIN_MERGE_MB*1024*1024);
    maxMergeSize = (long) (DEFAULT_MAX_MERGE_MB*1024*1024);
    // NOTE: in Java, if you cast a too-large double to long, as we are doing here, then it becomes Long.MAX_VALUE
    maxMergeSizeForForcedMerge = (long) (DEFAULT_MAX_MERGE_MB_FOR_FORCED_MERGE*1024*1024);
  }
  
  @Override
  protected long size(SegmentCommitInfo info, MergeContext mergeContext) throws IOException {
    return sizeBytes(info, mergeContext);
  }

  
Determines the largest segment (measured by total
 byte size of the segment's files, in MB) that may be
 merged with other segments.  Small values (e.g., less
 than 50 MB) are best for interactive indexing, as this
 limits the length of pauses while indexing to a few
 seconds.  Larger values are best for batched indexing
 and speedier searches.
 
Note that LogMergePolicy.setMaxMergeDocs is also used to check whether a segment is too large for merging (it's either or)./** <p>Determines the largest segment (measured by total
   *  byte size of the segment's files, in MB) that may be
   *  merged with other segments.  Small values (e.g., less
   *  than 50 MB) are best for interactive indexing, as this
   *  limits the length of pauses while indexing to a few
   *  seconds.  Larger values are best for batched indexing
   *  and speedier searches.</p>
   *
   *  <p>Note that {@link #setMaxMergeDocs} is also
   *  used to check whether a segment is too large for
   *  merging (it's either or).</p>*/
  public void setMaxMergeMB(double mb) {
    maxMergeSize = (long) (mb*1024*1024);
  }

  
Returns the largest segment (measured by total byte
 size of the segment's files, in MB) that may be merged
 with other segments.
 @see #setMaxMergeMB /** Returns the largest segment (measured by total byte
   *  size of the segment's files, in MB) that may be merged
   *  with other segments.
   *  @see #setMaxMergeMB */
  public double getMaxMergeMB() {
    return ((double) maxMergeSize)/1024/1024;
  }

  
Determines the largest segment (measured by total byte size of the segment's files, in MB) that may be merged with other segments during forceMerge. Setting it low will leave the index with more than 1 segment, even if IndexWriter.forceMerge is called./** <p>Determines the largest segment (measured by total
   *  byte size of the segment's files, in MB) that may be
   *  merged with other segments during forceMerge. Setting
   *  it low will leave the index with more than 1 segment,
   *  even if {@link IndexWriter#forceMerge} is called.*/
  public void setMaxMergeMBForForcedMerge(double mb) {
    maxMergeSizeForForcedMerge = (long) (mb*1024*1024);
  }

  
Returns the largest segment (measured by total byte
 size of the segment's files, in MB) that may be merged
 with other segments during forceMerge.
 @see #setMaxMergeMBForForcedMerge /** Returns the largest segment (measured by total byte
   *  size of the segment's files, in MB) that may be merged
   *  with other segments during forceMerge.
   *  @see #setMaxMergeMBForForcedMerge */
  public double getMaxMergeMBForForcedMerge() {
    return ((double) maxMergeSizeForForcedMerge)/1024/1024;
  }

  
Sets the minimum size for the lowest level segments.
Any segments below this size are considered to be on
the same level (even if they vary drastically in size)
and will be merged whenever there are mergeFactor of
them.  This effectively truncates the "long tail" of
small segments that would otherwise be created into a
single level.  If you set this too large, it could
greatly increase the merging cost during indexing (if
you flush many small segments). /** Sets the minimum size for the lowest level segments.
   * Any segments below this size are considered to be on
   * the same level (even if they vary drastically in size)
   * and will be merged whenever there are mergeFactor of
   * them.  This effectively truncates the "long tail" of
   * small segments that would otherwise be created into a
   * single level.  If you set this too large, it could
   * greatly increase the merging cost during indexing (if
   * you flush many small segments). */
  public void setMinMergeMB(double mb) {
    minMergeSize = (long) (mb*1024*1024);
  }

  
Get the minimum size for a segment to remain
 un-merged.
 @see #setMinMergeMB /** Get the minimum size for a segment to remain
   *  un-merged.
   *  @see #setMinMergeMB **/
  public double getMinMergeMB() {
    return ((double) minMergeSize)/1024/1024;
  }
}