org.apache.lucene.index

## Class LogByteSizeMergePolicy

- java.lang.Object
- - org.apache.lucene.index.MergePolicy
  - - org.apache.lucene.index.LogMergePolicy
    - - org.apache.lucene.index.LogByteSizeMergePolicy

- All Implemented Interfaces:
    Closeable, AutoCloseable, Cloneable

      public class LogByteSizeMergePolicy
      extends LogMergePolicy

  This is a `LogMergePolicy` that measures size of a segment as the total byte size of the segment's files.

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.apache.lucene.index.MergePolicy

      `MergePolicy.MergeAbortedException, MergePolicy.MergeException, MergePolicy.MergeSpecification, MergePolicy.MergeTrigger, MergePolicy.OneMerge`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static double` | `DEFAULT_MAX_MERGE_MB` Default maximum segment size.
    `static double` | `DEFAULT_MAX_MERGE_MB_FOR_FORCED_MERGE` Default maximum segment size.
    `static double` | `DEFAULT_MIN_MERGE_MB` Default minimum segment size.

    - ### Fields inherited from class org.apache.lucene.index.LogMergePolicy

      `calibrateSizeByDeletes, DEFAULT_MAX_CFS_SEGMENT_SIZE, DEFAULT_MAX_MERGE_DOCS, DEFAULT_MERGE_FACTOR, DEFAULT_NO_CFS_RATIO, LEVEL_LOG_SPAN, maxCFSSegmentSize, maxMergeDocs, maxMergeSize, maxMergeSizeForForcedMerge, mergeFactor, minMergeSize, noCFSRatio, useCompoundFile`

    - ### Fields inherited from class org.apache.lucene.index.MergePolicy

      `writer`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `LogByteSizeMergePolicy()` Sole constructor, setting all settings to their defaults.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `double` | `getMaxMergeMB()` Returns the largest segment (measured by total byte size of the segment's files, in MB) that may be merged with other segments.
    `double` | `getMaxMergeMBForForcedMerge()` 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.
    `double` | `getMinMergeMB()` Get the minimum size for a segment to remain un-merged.
    `void` | `setMaxMergeMB(double mb)` Determines the largest segment (measured by total byte size of the segment's files, in MB) that may be merged with other segments.
    `void` | `setMaxMergeMBForForcedMerge(double mb)` 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.
    `void` | `setMinMergeMB(double mb)` Sets the minimum size for the lowest level segments.
    `protected long` | `size(SegmentInfoPerCommit info)` Return the size of the provided `SegmentInfoPerCommit`.

    - ### Methods inherited from class org.apache.lucene.index.LogMergePolicy

      `close, findForcedDeletesMerges, findForcedMerges, findMerges, getCalibrateSizeByDeletes, getMaxCFSSegmentSizeMB, getMaxMergeDocs, getMergeFactor, getNoCFSRatio, getUseCompoundFile, isMerged, isMerged, message, setCalibrateSizeByDeletes, setMaxCFSSegmentSizeMB, setMaxMergeDocs, setMergeFactor, setNoCFSRatio, setUseCompoundFile, sizeBytes, sizeDocs, toString, useCompoundFile, verbose`

    - ### Methods inherited from class org.apache.lucene.index.MergePolicy

      `clone, setIndexWriter`

    - ### Methods inherited from class java.lang.Object

      `equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### DEFAULT_MIN_MERGE_MB

          public static final double DEFAULT_MIN_MERGE_MB

      Default minimum segment size. @see setMinMergeMB
      See Also:
        Constant Field Values

    - #### DEFAULT_MAX_MERGE_MB

          public static final double DEFAULT_MAX_MERGE_MB

      Default maximum segment size. A segment of this size or larger will never be merged. @see setMaxMergeMB
      See Also:
        Constant Field Values

    - #### DEFAULT_MAX_MERGE_MB_FOR_FORCED_MERGE

          public static final double DEFAULT_MAX_MERGE_MB_FOR_FORCED_MERGE

      Default maximum segment size. A segment of this size or larger will never be merged during forceMerge. @see setMaxMergeMBForForceMerge
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### LogByteSizeMergePolicy

          public LogByteSizeMergePolicy()

      Sole constructor, setting all settings to their defaults.

  - ### Method Detail

    - #### size

          protected long size(SegmentInfoPerCommit info)
                       throws IOException

      Description copied from class: `LogMergePolicy`
      Return the size of the provided `SegmentInfoPerCommit`.
      Specified by:
        `size` in class `LogMergePolicy`
      Throws:
        `IOException`

    - #### setMaxMergeMB

          public void setMaxMergeMB(double mb)

      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(int)` is also used to check whether a segment is too large for merging (it's either or).

    - #### getMaxMergeMB

          public double getMaxMergeMB()

      Returns the largest segment (measured by total byte size of the segment's files, in MB) that may be merged with other segments.
      See Also:
        `setMaxMergeMB(double)`

    - #### setMaxMergeMBForForcedMerge

          public void setMaxMergeMBForForcedMerge(double mb)

      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(int)` is called.

    - #### getMaxMergeMBForForcedMerge

          public double getMaxMergeMBForForcedMerge()

      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 Also:
        `setMaxMergeMBForForcedMerge(double)`

    - #### setMinMergeMB

          public void setMinMergeMB(double mb)

      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).

    - #### getMinMergeMB

          public double getMinMergeMB()

      Get the minimum size for a segment to remain un-merged.
      See Also:
        `setMinMergeMB(double)`

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