Package org.apache.lucene.index

Class UpgradeIndexMergePolicy

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, java.lang.Cloneable
    public class UpgradeIndexMergePolicy
extends MergePolicy
    This MergePolicy is used for upgrading all existing segments of an index when calling IndexWriter.forceMerge(int). All other methods delegate to the base MergePolicy given to the constructor. This allows for an as-cheap-as possible upgrade of an older index by only upgrading segments that are created by previous Lucene versions. forceMerge does no longer really merge; it is just used to "forceMerge" older segment versions away.

    In general one would use IndexUpgrader, but for a fully customizeable upgrade, you can use this like any other MergePolicy and call IndexWriter.forceMerge(int): 

      IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_XX, new KeywordAnalyzer());
  iwc.setMergePolicy(new UpgradeIndexMergePolicy(iwc.getMergePolicy()));
  IndexWriter w = new IndexWriter(dir, iwc);
  w.forceMerge(1);
  w.close();

    Warning: This merge policy may reorder documents if the index was partially upgraded before calling forceMerge (e.g., documents were added). If your application relies on "monotonicity" of doc IDs (which means that the order in which the documents were added to the index is preserved), do a forceMerge(1) instead. Please note, the delegate MergePolicy may also reorder documents.

    See Also:
    IndexUpgrader

    • Constructor Detail

      • UpgradeIndexMergePolicy

        public UpgradeIndexMergePolicy​(MergePolicy base)
        Wrap the given MergePolicy and intercept forceMerge requests to only upgrade segments written with previous Lucene versions.

    • Method Detail

      • findMerges

        public MergePolicy.MergeSpecification findMerges​(MergePolicy.MergeTrigger mergeTrigger,
                                                 SegmentInfos segmentInfos)
                                          throws java.io.IOException
        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
        Throws:
        java.io.IOException

      • findForcedMerges

        public MergePolicy.MergeSpecification findForcedMerges​(SegmentInfos segmentInfos,
                                                       int maxSegmentCount,
                                                       java.util.Map<SegmentCommitInfo,​java.lang.Boolean> segmentsToMerge)
                                                throws java.io.IOException
        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.
        Throws:
        java.io.IOException

      • findForcedDeletesMerges

        public MergePolicy.MergeSpecification findForcedDeletesMerges​(SegmentInfos segmentInfos)
                                                       throws java.io.IOException
        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
        Throws:
        java.io.IOException

      • close

        public void close()
        Description copied from class: MergePolicy
        Release all resources for the policy.
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Specified by:
        close in class MergePolicy

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object