org.apache.lucene.index
Class MergePolicy

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

Direct Known Subclasses:

LogMergePolicy

public abstract class MergePolicy
extends Object

Expert: a MergePolicy determines the sequence of primitive merge operations to be used for overall merge and optimize operations.

Whenever the segments in an index have been altered by IndexWriter, either the addition of a newly flushed segment, addition of many segments from addIndexes* calls, or a previous merge that may now need to cascade, IndexWriter invokes findMerges(org.apache.lucene.index.SegmentInfos, org.apache.lucene.index.IndexWriter) to give the MergePolicy a chance to pick merges that are now required. This method returns a MergePolicy.MergeSpecification instance describing the set of merges that should be done, or null if no merges are necessary. When IndexWriter.optimize is called, it calls findMergesForOptimize(org.apache.lucene.index.SegmentInfos, org.apache.lucene.index.IndexWriter, int, java.util.Set) and the MergePolicy should then return the necessary merges.

Note that the policy can return more than one merge at a time. In this case, if the writer is using SerialMergeScheduler, the merges will be run sequentially but if it is using ConcurrentMergeScheduler they will be run concurrently.

The default MergePolicy is LogByteSizeMergePolicy.

NOTE: This API is new and still experimental (subject to change suddenly in the next release)

Nested Class Summary

static class	MergePolicy.MergeAbortedException
static class	MergePolicy.MergeException Exception thrown if there are any problems while executing a merge.
static class	MergePolicy.MergeSpecification A MergeSpecification instance provides the information necessary to perform multiple merges.
static class	MergePolicy.OneMerge OneMerge provides the information necessary to perform an individual primitive merge operation, resulting in a single new segment.

Constructor Summary

MergePolicy()

Method Summary

Methods inherited from class java.lang.Object

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

Constructor Detail

MergePolicy

public MergePolicy()