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.

Note

This API is experimental and might change in incompatible ways in the next release.

Inheritance
System.Object
SegmentInfos
Implements
System.Collections.Generic.IEnumerable<SegmentCommitInfo>
System.Collections.IEnumerable
Inherited Members
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
System.Object.ToString()
Namespace: Lucene.Net.Index
Assembly: Lucene.Net.dll
Syntax
public sealed class SegmentInfos : IEnumerable<SegmentCommitInfo>, IEnumerable

Constructors

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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

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FORMAT_SEGMENTS_GEN_CURRENT

Current format of segments.gen

Declaration
public static readonly int FORMAT_SEGMENTS_GEN_CURRENT
Field Value
Type Description
System.Int32
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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
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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
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VERSION_48

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

Declaration
public const int VERSION_48 = 2
Field Value
Type Description
System.Int32

Properties

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Count

Returns number of SegmentCommitInfos.

NOTE: This was size() in Lucene.

Declaration
public int Count { get; }
Property Value
Type Description
System.Int32
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Counter

Used to name new segments.

Declaration
public int Counter { get; set; }
Property Value
Type Description
System.Int32
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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.

Note

This API is experimental and might change in incompatible ways in the next release.

Declaration
public static int DefaultGenLookaheadCount { get; set; }
Property Value
Type Description
System.Int32
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Generation

Returns current generation.

Declaration
public long Generation { get; }
Property Value
Type Description
System.Int64
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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
System.IO.TextWriter
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Item[Int32]

Returns SegmentCommitInfo at the provided index.

This was info(int) in Lucene.

Declaration
public SegmentCommitInfo this[int index] { get; }
Parameters
Type Name Description
System.Int32 index
Property Value
Type Description
SegmentCommitInfo
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LastGeneration

Returns last succesfully read or written generation.

Declaration
public long LastGeneration { get; }
Property Value
Type Description
System.Int64
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Segments

Declaration
public IList<SegmentCommitInfo> Segments { get; }
Property Value
Type Description
System.Collections.Generic.IList<SegmentCommitInfo>
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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
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UseLegacySegmentNames

Setting this to true will generate the same file names that were used in 4.8.0-beta00001 through 4.8.0-beta00015. When writing more than 10 segments, these segment names were incompatible with prior versions of Lucene.NET and incompatible with Lucene 4.8.0.

This is only for reading codecs from the affected 4.8.0 beta versions, it is not recommended to use this setting for general use.

This must be set prior to opening an index at application startup. When setting it at other times the behavior is undefined.

Note that this property can also be set using the "useLegacySegmentNames" system property to "true" (such as setting the environment variable "lucene:useLegacySegmentNames"). System properties can also be injected by supplying a IConfigurationFactory at application startup through SetConfigurationFactory(IConfigurationFactory).

Declaration
public static bool UseLegacySegmentNames { get; set; }
Property Value
Type Description
System.Boolean
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UserData

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

Declaration
public IDictionary<string, string> UserData { get; }
Property Value
Type Description
System.Collections.Generic.IDictionary<System.String, System.String>
See Also
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Version

Version number when this SegmentInfos was generated.

Declaration
public long Version { get; }
Property Value
Type Description
System.Int64

Methods

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Add(SegmentCommitInfo)

Appends the provided SegmentCommitInfo.

Declaration
public void Add(SegmentCommitInfo si)
Parameters
Type Name Description
SegmentCommitInfo si
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AddAll(IEnumerable<SegmentCommitInfo>)

Appends the provided SegmentCommitInfos.

Declaration
public void AddAll(IEnumerable<SegmentCommitInfo> sis)
Parameters
Type Name Description
System.Collections.Generic.IEnumerable<SegmentCommitInfo> sis
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AsList()

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

Declaration
public IList<SegmentCommitInfo> AsList()
Returns
Type Description
System.Collections.Generic.IList<SegmentCommitInfo>
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Changed()

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

Declaration
public void Changed()
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Clear()

Clear all SegmentCommitInfos.

Declaration
public void Clear()
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Clone()

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

Declaration
public object Clone()
Returns
Type Description
System.Object
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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
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GetEnumerator()

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

Declaration
public IEnumerator<SegmentCommitInfo> GetEnumerator()
Returns
Type Description
System.Collections.Generic.IEnumerator<SegmentCommitInfo>
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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
System.Collections.Generic.ICollection<System.String>
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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
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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
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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
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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
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GetNextSegmentFileName()

Get the next segments_N filename that will be written.

Declaration
public string GetNextSegmentFileName()
Returns
Type Description
System.String
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GetSegmentsFileName()

Get the segments_N filename in use by this segment infos.

Declaration
public string GetSegmentsFileName()
Returns
Type Description
System.String
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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
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Read(Directory, String)

Read a particular segmentFileName. Note that this may throw an System.IO.IOException 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

System.IO.IOException

if there is a low-level IO error

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Remove(SegmentCommitInfo)

Remove the provided SegmentCommitInfo.

WARNING: O(N) cost

Declaration
public void Remove(SegmentCommitInfo si)
Parameters
Type Name Description
SegmentCommitInfo si
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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
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Write3xInfo(Directory, SegmentInfo, IOContext)

Declaration
[Obsolete]
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
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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!

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration
public static void WriteSegmentsGen(Directory dir, long generation)
Parameters
Type Name Description
Directory dir
System.Int64 generation

Explicit Interface Implementations

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IEnumerable.GetEnumerator()

Declaration
IEnumerator IEnumerable.GetEnumerator()
Returns
Type Description
System.Collections.IEnumerator

Implements

System.Collections.Generic.IEnumerable<T>
System.Collections.IEnumerable