Class MergePolicy

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(SegmentInfos) 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(SegmentInfos, Int32, ISet<SegmentInfo>) 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)

NOTE: This class typically requires access to package-private APIs (e.g. SegmentInfos) to do its job; if you implement your own MergePolicy, you'll need to put it in package Lucene.Net.Index in order to use these APIs.

Inheritance
System.Object
MergePolicy
LogMergePolicy
Namespace:
Assembly: Lucene.Net.NetCore.dll
Syntax
public abstract class MergePolicy : IDisposable

Constructors

Name Description
MergePolicy(IndexWriter)

Fields

Name Description
writer

Methods

Name Description
Close()

Release all resources for the policy.
Dispose()

Release all resources for the policy.
Dispose(Boolean)
FindMerges(SegmentInfos)

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.
FindMergesForOptimize(SegmentInfos, Int32, ISet<SegmentInfo>)

Determine what set of merge operations is necessary in order to optimize the index. IndexWriter calls this when its Optimize() method is called. This call is always synchronized on the IndexWriter instance so only one thread at a time will call this method.
FindMergesToExpungeDeletes(SegmentInfos)

Determine what set of merge operations is necessary in order to expunge all deletes from the index.
UseCompoundDocStore(SegmentInfos)

Returns true if the doc store files should use the compound file format.
UseCompoundFile(SegmentInfos, SegmentInfo)

Returns true if a newly flushed (not from merge) segment should use the compound file format.