Package org.apache.lucene.index

Class LogMergePolicy

    • Field Detail

      • LEVEL_LOG_SPAN

        public static final double LEVEL_LOG_SPAN
        Defines the allowed range of log(size) for each level. A level is computed by taking the max segment log size, minus LEVEL_LOG_SPAN, and finding all segments falling within that range.
        See Also:
        Constant Field Values

      • DEFAULT_MERGE_FACTOR

        public static final int DEFAULT_MERGE_FACTOR
        Default merge factor, which is how many segments are merged at a time
        See Also:
        Constant Field Values

      • DEFAULT_MAX_MERGE_DOCS

        public static final int DEFAULT_MAX_MERGE_DOCS
        Default maximum segment size. A segment of this size or larger will never be merged. @see setMaxMergeDocs
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        Constant Field Values

      • mergeFactor

        protected int mergeFactor
        How many segments to merge at a time.

      • minMergeSize

        protected long minMergeSize
        Any segments whose size is smaller than this value will be rounded up to this value. This ensures that tiny segments are aggressively merged.

      • maxMergeSize

        protected long maxMergeSize
        If the size of a segment exceeds this value then it will never be merged.

      • maxMergeSizeForForcedMerge

        protected long maxMergeSizeForForcedMerge
        If the size of a segment exceeds this value then it will never be merged during IndexWriter.forceMerge(int).

      • maxMergeDocs

        protected int maxMergeDocs
        If a segment has more than this many documents then it will never be merged.

      • calibrateSizeByDeletes

        protected boolean calibrateSizeByDeletes
        If true, we pro-rate a segment's size by the percentage of non-deleted documents.

    • Constructor Detail

      • LogMergePolicy

        public LogMergePolicy()
        Sole constructor. (For invocation by subclass constructors, typically implicit.)

    • Method Detail

      • verbose

        protected boolean verbose()
        Returns true if LMP is enabled in IndexWriter's infoStream.

      • message

        protected void message​(String message)
        Print a debug message to IndexWriter's infoStream.

      • getMergeFactor

        public int getMergeFactor()

        Returns the number of segments that are merged at once and also controls the total number of segments allowed to accumulate in the index.

      • setMergeFactor

        public void setMergeFactor​(int mergeFactor)
        Determines how often segment indices are merged by addDocument(). With smaller values, less RAM is used while indexing, and searches are faster, but indexing speed is slower. With larger values, more RAM is used during indexing, and while searches is slower, indexing is faster. Thus larger values (> 10) are best for batch index creation, and smaller values (< 10) for indices that are interactively maintained.

      • setCalibrateSizeByDeletes

        public void setCalibrateSizeByDeletes​(boolean calibrateSizeByDeletes)
        Sets whether the segment size should be calibrated by the number of deletes when choosing segments for merge.

      • getCalibrateSizeByDeletes

        public boolean getCalibrateSizeByDeletes()
        Returns true if the segment size should be calibrated by the number of deletes when choosing segments for merge.

      • findForcedMerges

        public MergePolicy.MergeSpecification findForcedMerges​(SegmentInfos infos,
                                                       int maxNumSegments,
                                                       Map<SegmentCommitInfo,​Boolean> segmentsToMerge)
                                                throws IOException
        Returns the merges necessary to merge the index down to a specified number of segments. This respects the maxMergeSizeForForcedMerge setting. By default, and assuming maxNumSegments=1, only one segment will be left in the index, where that segment has no deletions pending nor separate norms, and it is in compound file format if the current useCompoundFile setting is true. This method returns multiple merges (mergeFactor at a time) so the MergeScheduler in use may make use of concurrency.
        Specified by:
        findForcedMerges in class MergePolicy
        Parameters:
        infos - the total set of segments in the index
        maxNumSegments - 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.
        Throws:
        IOException

      • setMaxMergeDocs

        public void setMaxMergeDocs​(int maxMergeDocs)

        Determines the largest segment (measured by document count) that may be merged with other segments. Small values (e.g., less than 10,000) 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.

        The default value is Integer.MAX_VALUE.

        The default merge policy (LogByteSizeMergePolicy) also allows you to set this limit by net size (in MB) of the segment, using LogByteSizeMergePolicy.setMaxMergeMB(double).

      • getMaxMergeDocs

        public int getMaxMergeDocs()
        Returns the largest segment (measured by document count) that may be merged with other segments.
        See Also:
        setMaxMergeDocs(int)