org.apache.lucene.index

## Class NoMergePolicy

- java.lang.Object
- - org.apache.lucene.index.MergePolicy
  - - org.apache.lucene.index.NoMergePolicy

-     public final class NoMergePolicy
      extends MergePolicy

  A `MergePolicy` which never returns merges to execute. Use it if you want to prevent segment merges.

- - ### Nested Class Summary

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

      `MergePolicy.MergeAbortedException, MergePolicy.MergeContext, MergePolicy.MergeException, MergePolicy.MergeSpecification, MergePolicy.OneMerge, MergePolicy.OneMergeProgress`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static MergePolicy` | `INSTANCE` Singleton instance.

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

      `DEFAULT_MAX_CFS_SEGMENT_SIZE, DEFAULT_NO_CFS_RATIO, maxCFSSegmentSize, noCFSRatio`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `MergePolicy.MergeSpecification` | `findForcedDeletesMerges(SegmentInfos segmentInfos, MergePolicy.MergeContext mergeContext)` Determine what set of merge operations is necessary in order to expunge all deletes from the index.
    `MergePolicy.MergeSpecification` | `findForcedMerges(SegmentInfos segmentInfos, int maxSegmentCount, Map<SegmentCommitInfo,Boolean> segmentsToMerge, MergePolicy.MergeContext mergeContext)` Determine what set of merge operations is necessary in order to merge to `<=` the specified segment count.
    `MergePolicy.MergeSpecification` | `findFullFlushMerges(MergeTrigger mergeTrigger, SegmentInfos segmentInfos, MergePolicy.MergeContext mergeContext)` Identifies merges that we want to execute (synchronously) on commit.
    `MergePolicy.MergeSpecification` | `findMerges(MergeTrigger mergeTrigger, SegmentInfos segmentInfos, MergePolicy.MergeContext mergeContext)` Determine what set of merge operations are now necessary on the index.
    `double` | `getMaxCFSSegmentSizeMB()` Returns the largest size allowed for a compound file segment
    `double` | `getNoCFSRatio()` Returns current `noCFSRatio`.
    `boolean` | `keepFullyDeletedSegment(IOSupplier<CodecReader> readerIOSupplier)` Returns true if the segment represented by the given CodecReader should be keep even if it's fully deleted.
    `int` | `numDeletesToMerge(SegmentCommitInfo info, int delCount, IOSupplier<CodecReader> readerSupplier)` Returns the number of deletes that a merge would claim on the given segment.
    `void` | `setMaxCFSSegmentSizeMB(double v)` If a merged segment will be more than this value, leave the segment as non-compound file even if compound file is enabled.
    `void` | `setNoCFSRatio(double noCFSRatio)` If a merged segment will be more than this percentage of the total size of the index, leave the segment as non-compound file even if compound file is enabled.
    `protected long` | `size(SegmentCommitInfo info, MergePolicy.MergeContext context)` Return the byte size of the provided `SegmentCommitInfo`, pro-rated by percentage of non-deleted documents is set.
    `String` | `toString()`
    `boolean` | `useCompoundFile(SegmentInfos segments, SegmentCommitInfo newSegment, MergePolicy.MergeContext mergeContext)` Returns true if a new segment (regardless of its origin) should use the compound file format.

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

      `assertDelCount, isMerged, message, segString, verbose`

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

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

- - ### Field Detail

    - #### INSTANCE

          public static final MergePolicy INSTANCE

      Singleton instance.

  - ### Method Detail

    - #### findMerges

          public MergePolicy.MergeSpecification findMerges(MergeTrigger mergeTrigger,
                                                           SegmentInfos segmentInfos,
                                                           MergePolicy.MergeContext mergeContext)

      Description copied from class: `MergePolicy`
      Determine what set of merge operations are now necessary on the index. `IndexWriter` calls this whenever there is a change to the segments. This call is always synchronized on the `IndexWriter` instance so only one thread at a time will call this method.
      Specified by:
        `findMerges` in class `MergePolicy`
      Parameters:
        `mergeTrigger` - the event that triggered the merge
        `segmentInfos` - the total set of segments in the index
        `mergeContext` - the IndexWriter to find the merges on

    - #### findForcedMerges

          public MergePolicy.MergeSpecification findForcedMerges(SegmentInfos segmentInfos,
                                                                 int maxSegmentCount,
                                                                 Map<SegmentCommitInfo,Boolean> segmentsToMerge,
                                                                 MergePolicy.MergeContext mergeContext)

      Description copied from class: `MergePolicy`
      Determine what set of merge operations is necessary in order to merge to `<=` the specified segment count. `IndexWriter` calls this when its `IndexWriter.forceMerge(int)` method is called. This call is always synchronized on the `IndexWriter` instance so only one thread at a time will call this method.
      Specified by:
        `findForcedMerges` in class `MergePolicy`
      Parameters:
        `segmentInfos` - the total set of segments in the index
        `maxSegmentCount` - requested maximum number of segments in the index (currently this is always 1)
        `segmentsToMerge` - contains the specific SegmentInfo instances that must be merged away. This may be a subset of all SegmentInfos. If the value is True for a given SegmentInfo, that means this segment was an original segment present in the to-be-merged index; else, it was a segment produced by a cascaded merge.
        `mergeContext` - the MergeContext to find the merges on

    - #### findForcedDeletesMerges

          public MergePolicy.MergeSpecification findForcedDeletesMerges(SegmentInfos segmentInfos,
                                                                        MergePolicy.MergeContext mergeContext)

      Description copied from class: `MergePolicy`
      Determine what set of merge operations is necessary in order to expunge all deletes from the index.
      Specified by:
        `findForcedDeletesMerges` in class `MergePolicy`
      Parameters:
        `segmentInfos` - the total set of segments in the index
        `mergeContext` - the MergeContext to find the merges on

    - #### findFullFlushMerges

          public MergePolicy.MergeSpecification findFullFlushMerges(MergeTrigger mergeTrigger,
                                                                    SegmentInfos segmentInfos,
                                                                    MergePolicy.MergeContext mergeContext)

      Description copied from class: `MergePolicy`
      Identifies merges that we want to execute (synchronously) on commit. By default, this will do no merging on commit. If you implement this method in your `MergePolicy` you must also set a non-zero timeout using `IndexWriterConfig.setMaxFullFlushMergeWaitMillis(long)`. Any merges returned here will make `IndexWriter.commit()`, `IndexWriter.prepareCommit()` or `IndexWriter.getReader(boolean, boolean)` block until the merges complete or until `LiveIndexWriterConfig.getMaxFullFlushMergeWaitMillis()` has elapsed. This may be used to merge small segments that have just been flushed, reducing the number of segments in the point in time snapshot. If a merge does not complete in the allotted time, it will continue to execute, and eventually finish and apply to future point in time snapshot, but will not be reflected in the current one. If a `MergePolicy.OneMerge` in the returned `MergePolicy.MergeSpecification` includes a segment already included in a registered merge, then `IndexWriter.commit()` or `IndexWriter.prepareCommit()` will throw a `IllegalStateException`. Use `MergePolicy.MergeContext.getMergingSegments()` to determine which segments are currently registered to merge.
      Overrides:
        `findFullFlushMerges` in class `MergePolicy`
      Parameters:
        `mergeTrigger` - the event that triggered the merge (COMMIT or GET_READER).
        `segmentInfos` - the total set of segments in the index (while preparing the commit)
        `mergeContext` - the MergeContext to find the merges on, which should be used to determine which segments are already in a registered merge (see `MergePolicy.MergeContext.getMergingSegments()`).

    - #### useCompoundFile

          public boolean useCompoundFile(SegmentInfos segments,
                                         SegmentCommitInfo newSegment,
                                         MergePolicy.MergeContext mergeContext)

      Description copied from class: `MergePolicy`
      Returns true if a new segment (regardless of its origin) should use the compound file format. The default implementation returns `true` iff the size of the given mergedInfo is less or equal to `MergePolicy.getMaxCFSSegmentSizeMB()` and the size is less or equal to the TotalIndexSize * `MergePolicy.getNoCFSRatio()` otherwise `false`.
      Overrides:
        `useCompoundFile` in class `MergePolicy`

    - #### size

          protected long size(SegmentCommitInfo info,
                              MergePolicy.MergeContext context)
                       throws IOException

      Description copied from class: `MergePolicy`
      Return the byte size of the provided `SegmentCommitInfo`, pro-rated by percentage of non-deleted documents is set.
      Overrides:
        `size` in class `MergePolicy`
      Throws:
        `IOException`

    - #### getNoCFSRatio

          public double getNoCFSRatio()

      Description copied from class: `MergePolicy`
      Returns current `noCFSRatio`.
      Overrides:
        `getNoCFSRatio` in class `MergePolicy`
      See Also:
        `MergePolicy.setNoCFSRatio(double)`

    - #### getMaxCFSSegmentSizeMB

          public double getMaxCFSSegmentSizeMB()

      Description copied from class: `MergePolicy`
      Returns the largest size allowed for a compound file segment
      Overrides:
        `getMaxCFSSegmentSizeMB` in class `MergePolicy`

    - #### setMaxCFSSegmentSizeMB

          public void setMaxCFSSegmentSizeMB(double v)

      Description copied from class: `MergePolicy`
      If a merged segment will be more than this value, leave the segment as non-compound file even if compound file is enabled. Set this to Double.POSITIVE_INFINITY (default) and noCFSRatio to 1.0 to always use CFS regardless of merge size.
      Overrides:
        `setMaxCFSSegmentSizeMB` in class `MergePolicy`

    - #### setNoCFSRatio

          public void setNoCFSRatio(double noCFSRatio)

      Description copied from class: `MergePolicy`
      If a merged segment will be more than this percentage of the total size of the index, leave the segment as non-compound file even if compound file is enabled. Set to 1.0 to always use CFS regardless of merge size.
      Overrides:
        `setNoCFSRatio` in class `MergePolicy`

    - #### keepFullyDeletedSegment

          public boolean keepFullyDeletedSegment(IOSupplier<CodecReader> readerIOSupplier)
                                          throws IOException

      Description copied from class: `MergePolicy`
      Returns true if the segment represented by the given CodecReader should be keep even if it's fully deleted. This is useful for testing of for instance if the merge policy implements retention policies for soft deletes.
      Overrides:
        `keepFullyDeletedSegment` in class `MergePolicy`
      Throws:
        `IOException`

    - #### numDeletesToMerge

          public int numDeletesToMerge(SegmentCommitInfo info,
                                       int delCount,
                                       IOSupplier<CodecReader> readerSupplier)
                                throws IOException

      Description copied from class: `MergePolicy`
      Returns the number of deletes that a merge would claim on the given segment. This method will by default return the sum of the del count on disk and the pending delete count. Yet, subclasses that wrap merge readers might modify this to reflect deletes that are carried over to the target segment in the case of soft deletes. Soft deletes all deletes to survive across merges in order to control when the soft-deleted data is claimed.
      Overrides:
        `numDeletesToMerge` in class `MergePolicy`
      Parameters:
        `info` - the segment info that identifies the segment
        `delCount` - the number deleted documents for this segment
        `readerSupplier` - a supplier that allows to obtain a `CodecReader` for this segment
      Throws:
        `IOException`
      See Also:
        `IndexWriter.softUpdateDocument(Term, Iterable, Field...)`, `IndexWriterConfig.setSoftDeletesField(String)`

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`

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