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:

• Header --> WriteHeader(DataOutput, String, Int32)
• GenHeader, NameCounter, SegCount, DeletionCount --> WriteInt32(Int32)
• Generation, Version, DelGen, Checksum, FieldInfosGen --> WriteInt64(Int64)
• SegName, SegCodec --> WriteString(String)
• CommitUserData --> WriteStringStringMap(IDictionary<String, String>)
• UpdatesFiles --> WriteStringSet(ISet<String>)
• Footer --> WriteFooter(IndexOutput)

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.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk

Inheritance

System.Object

SegmentInfos

Namespace: Lucene.Net.Index

Assembly: Lucene.Net.dll

Syntax

public sealed class SegmentInfos : IEnumerable<SegmentCommitInfo>

Constructors

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.

Declaration

public SegmentInfos()

Fields

FORMAT_SEGMENTS_GEN_CURRENT

Current format of segments.gen

Declaration

public static readonly int FORMAT_SEGMENTS_GEN_CURRENT

Field Value

Type	Description
System.Int32

VERSION_40

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

Declaration

public static readonly int VERSION_40

Field Value

Type	Description
System.Int32

VERSION_46

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

Declaration

public static readonly int VERSION_46

Field Value

Type	Description
System.Int32

VERSION_48

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

Declaration

public static readonly int VERSION_48

Field Value

Type	Description
System.Int32

Properties

Count

Returns number of SegmentCommitInfos.

NOTE: This was size() in Lucene.

Declaration

public int Count { get; }

Property Value

Type	Description
System.Int32

Counter

Used to name new segments.

Declaration

public int Counter { get; set; }

Property Value

Type	Description
System.Int32

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.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk

Declaration

public static int DefaultGenLookaheadCount { get; set; }

Property Value

Type	Description
System.Int32

Generation

Returns current generation.

Declaration

public long Generation { get; }

Property Value

Type	Description
System.Int64

InfoStream

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

Declaration

public static TextWriter InfoStream { get; set; }

Property Value

Type	Description
TextWriter

LastGeneration

Returns last succesfully read or written generation.

Declaration

public long LastGeneration { get; }

Property Value

Type	Description
System.Int64

Segments

Declaration

public IList<SegmentCommitInfo> Segments { get; }

Property Value

Type	Description
IList<SegmentCommitInfo>

TotalDocCount

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

Declaration

public int TotalDocCount { get; }

Property Value

Type	Description
System.Int32

UserData

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

Declaration

public IDictionary<string, string> UserData { get; }

Property Value

Type	Description
IDictionary<System.String, System.String>

See Also

Commit()

Version

Version number when this SegmentInfos was generated.

Declaration

public long Version { get; }

Property Value

Type	Description
System.Int64

Methods

Add(SegmentCommitInfo)

Appends the provided SegmentCommitInfo.

Declaration

public void Add(SegmentCommitInfo si)

Parameters

Type	Name	Description
SegmentCommitInfo	si

AddAll(IEnumerable<SegmentCommitInfo>)

Appends the provided SegmentCommitInfos.

Declaration

public void AddAll(IEnumerable<SegmentCommitInfo> sis)

Parameters

Type	Name	Description
IEnumerable<SegmentCommitInfo>	sis

AsList()

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

Declaration

public IList<SegmentCommitInfo> AsList()

Returns

Type	Description
IList<SegmentCommitInfo>

Changed()

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

Declaration

public void Changed()

Clear()

Clear all SegmentCommitInfos.

Declaration

public void Clear()

Clone()

Returns a copy of this instance, also copying each SegmentInfo.

Declaration

public object Clone()

Returns

Type	Description
System.Object

GenerationFromSegmentsFileName(String)

Parse the generation off the segments file name and return it.

Declaration

public static long GenerationFromSegmentsFileName(string fileName)

Parameters

Type	Name	Description
System.String	fileName

Returns

Type	Description
System.Int64

GetEnumerator()

Returns an unmodifiable IEnumerator{SegmentCommitInfo} of contained segments in order.

Declaration

public IEnumerator<SegmentCommitInfo> GetEnumerator()

Returns

Type	Description
IEnumerator<SegmentCommitInfo>

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.

Declaration

public ICollection<string> GetFiles(Directory dir, bool includeSegmentsFile)

Parameters

Type	Name	Description
Directory	dir
System.Boolean	includeSegmentsFile

Returns

Type	Description
ICollection<System.String>

GetLastCommitGeneration(Directory)

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

Declaration

public static long GetLastCommitGeneration(Directory directory)

Parameters

Type	Name	Description
Directory	directory	directory to search for the latest segments_N file

Returns

Type	Description
System.Int64

GetLastCommitGeneration(String[])

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

Declaration

public static long GetLastCommitGeneration(string[] files)

Parameters

Type	Name	Description
System.String[]	files	array of file names to check

Returns

Type	Description
System.Int64

GetLastCommitSegmentsFileName(Directory)

Get the filename of the segments_N file for the most recent commit to the index in this Directory.

Declaration

public static string GetLastCommitSegmentsFileName(Directory directory)

Parameters

Type	Name	Description
Directory	directory	directory to search for the latest segments_N file

Returns

Type	Description
System.String

GetLastCommitSegmentsFileName(String[])

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

Declaration

public static string GetLastCommitSegmentsFileName(string[] files)

Parameters

Type	Name	Description
System.String[]	files	array of file names to check

Returns

Type	Description
System.String

GetNextSegmentFileName()

Get the next segments_N filename that will be written.

Declaration

public string GetNextSegmentFileName()

Returns

Type	Description
System.String

GetSegmentsFileName()

Get the segments_N filename in use by this segment infos.

Declaration

public string GetSegmentsFileName()

Returns

Type	Description
System.String

Info(Int32)

Returns SegmentCommitInfo at the provided index.

Declaration

public SegmentCommitInfo Info(int i)

Parameters

Type	Name	Description
System.Int32	i

Returns

Type	Description
SegmentCommitInfo

Read(Directory)

Find the latest commit (segments_N file) and load all SegmentCommitInfos.

Declaration

public void Read(Directory directory)

Parameters

Type	Name	Description
Directory	directory

Read(Directory, String)

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

Declaration

public void Read(Directory directory, string segmentFileName)

Parameters

Type	Name	Description
Directory	directory	directory containing the segments file
System.String	segmentFileName	segment file to load

Exceptions

Type	Condition
CorruptIndexException	if the index is corrupt

Remove(SegmentCommitInfo)

Remove the provided SegmentCommitInfo.

WARNING: O(N) cost

Declaration

public void Remove(SegmentCommitInfo si)

Parameters

Type	Name	Description
SegmentCommitInfo	si

ToString(Directory)

Returns readable description of this segment.

Declaration

public string ToString(Directory directory)

Parameters

Type	Name	Description
Directory	directory

Returns

Type	Description
System.String

Write3xInfo(Directory, SegmentInfo, IOContext)

Declaration

public static string Write3xInfo(Directory dir, SegmentInfo si, IOContext context)

Parameters

Type	Name	Description
Directory	dir
SegmentInfo	si
IOContext	context

Returns

Type	Description
System.String

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!

This is a Lucene.NET INTERNAL API, use at your own risk

Declaration

public static void WriteSegmentsGen(Directory dir, long generation)

Parameters

Type	Name	Description
Directory	dir
System.Int64	generation