Class SegmentInfos

A collection of segmentInfo objects with methods for operating on those segments in relation to the file system.

The active segments in the index are stored in the segment info file, segments_N. There may be one or more segments_N files in the index; however, the one with the largest generation is the active one (when older segments_N files are present it's because they temporarily cannot be deleted, or, a writer is in the process of committing, or a custom IndexDeletionPolicy is in use). This file lists each segment by name and has details about the codec and generation of deletes.

There is also a file segments.gen. this file contains the current generation (the _N in segments_N) of the index. This is used only as a fallback in case the current generation cannot be accurately determined by directory listing alone (as is the case for some NFS clients with time-based directory cache expiration). This file simply contains an WriteInt32(Int32) version header (FORMAT_SEGMENTS_GEN_CURRENT), followed by the generation recorded as WriteInt64(Int64), written twice.

Files:

  • segments.gen: GenHeader, Generation, Generation, Footer
  • segments_N: Header, Version, NameCounter, SegCount, <SegName, SegCodec, DelGen, DeletionCount, FieldInfosGen, UpdatesFiles>SegCount, CommitUserData, Footer

Data types:

Field Descriptions:

  • Version counts how often the index has been changed by adding or deleting documents.
  • NameCounter is used to generate names for new segment files.
  • SegName is the name of the segment, and is used as the file name prefix for all of the files that compose the segment's index.
  • DelGen is the generation count of the deletes file. If this is -1, there are no deletes. Anything above zero means there are deletes stored by LiveDocsFormat.
  • DeletionCount records the number of deleted documents in this segment.
  • SegCodec is the Name of the Codec that encoded this segment.
  • CommitUserData stores an optional user-supplied opaque that was passed to SetCommitData(IDictionary<String, String>).
  • FieldInfosGen is the generation count of the fieldInfos file. If this is -1, there are no updates to the fieldInfos in that segment. Anything above zero means there are updates to fieldInfos stored by FieldInfosFormat.
  • UpdatesFiles stores the list of files that were updated in that segment.

@lucene.experimental

Inheritance
System.Object
SegmentInfos
Assembly: DistributedLucene.Net.dll
Syntax
public sealed class SegmentInfos : IEnumerable<SegmentCommitInfo>

Constructors

Name Description
SegmentInfos()

Sole constructor. Typically you call this and then use Read(Directory) or Read(Directory, String) to populate each SegmentCommitInfo. Alternatively, you can add/remove your own SegmentCommitInfos.

Fields

Name Description
FORMAT_SEGMENTS_GEN_CURRENT

Current format of segments.gen

VERSION_40

The file format version for the segments_N codec header, up to 4.5.

VERSION_46

The file format version for the segments_N codec header, since 4.6+.

VERSION_48

The file format version for the segments_N codec header, since 4.8+

Properties

Name Description
Count

Returns number of SegmentCommitInfos.

NOTE: This was size() in Lucene.
Counter

Used to name new segments.

DefaultGenLookaheadCount

Gets or Sets the Lucene.Net.Index.SegmentInfos.defaultGenLookaheadCount.

Advanced: set how many times to try incrementing the gen when loading the segments file. this only runs if the primary (listing directory) and secondary (opening segments.gen file) methods fail to find the segments file.

@lucene.experimental
Generation

Returns current generation.

InfoStream

If non-null, information about retries when loading the segments file will be printed to this.
LastGeneration

Returns last succesfully read or written generation.

Segments
TotalDocCount

Returns sum of all segment's docCounts. Note that this does not include deletions
UserData

Gets Lucene.Net.Index.SegmentInfos.userData saved with this commit.
Version

Version number when this SegmentInfos was generated.

Methods

Name Description
Add(SegmentCommitInfo)

Appends the provided SegmentCommitInfo.

AddAll(IEnumerable<SegmentCommitInfo>)

Appends the provided SegmentCommitInfos.

AsList()

Returns all contained segments as an unmodifiable IList{SegmentCommitInfo} view.

Changed()

Call this before committing if changes have been made to the segments.
Clear()

Clear all SegmentCommitInfos.

Clone()

Returns a copy of this instance, also copying each SegmentInfo.
GenerationFromSegmentsFileName(String)

Parse the generation off the segments file name and return it.
GetEnumerator()

Returns an unmodifiable IEnumerator{SegmentCommitInfo} of contained segments in order.
GetFiles(Directory, Boolean)

Returns all file names referenced by SegmentInfo instances matching the provided Directory (ie files associated with any "external" segments are skipped). The returned collection is recomputed on each invocation.
GetLastCommitGeneration(Directory)

Get the generation of the most recent commit to the index in this directory (N in the segments_N file).
GetLastCommitGeneration(String[])

Get the generation of the most recent commit to the list of index files (N in the segments_N file).
GetLastCommitSegmentsFileName(Directory)

Get the filename of the segments_N file for the most recent commit to the index in this Directory.
GetLastCommitSegmentsFileName(String[])

Get the filename of the segments_N file for the most recent commit in the list of index files.
GetNextSegmentFileName()

Get the next segments_N filename that will be written.
GetSegmentsFileName()

Get the segments_N filename in use by this segment infos.
Info(Int32)

Returns SegmentCommitInfo at the provided index.
Read(Directory)

Find the latest commit (segments_N file) and load all SegmentCommitInfos.
Read(Directory, String)

Read a particular segmentFileName. Note that this may throw an if a commit is in process.
Remove(SegmentCommitInfo)

Remove the provided SegmentCommitInfo.

WARNING: O(N) cost
ToString(Directory)

Returns readable description of this segment.

Write3xInfo(Directory, SegmentInfo, IOContext)
WriteSegmentsGen(Directory, Int64)

A utility for writing the SEGMENTS_GEN file to a Directory.

NOTE: this is an internal utility which is kept public so that it's accessible by code from other packages. You should avoid calling this method unless you're absolutely sure what you're doing!

@lucene.internal

Extension Methods