SegmentInfos (Lucene 5.5.0 API)

java.lang.Object
- org.apache.lucene.index.SegmentInfos

All Implemented Interfaces:

Cloneable, Iterable<SegmentCommitInfo>
```
public final class SegmentInfos
extends Object
implements Cloneable, Iterable<SegmentCommitInfo>
```
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 custom IndexDeletionPolicy is in use). This file lists each segment by name and has details about the codec and generation of deletes.

Files:
- segments_N: Header, LuceneVersion, Version, NameCounter, SegCount, MinSegmentLuceneVersion, <SegName, HasSegID, SegID, SegCodec, DelGen, DeletionCount, FieldInfosGen, DocValuesGen, UpdatesFiles>^SegCount, CommitUserData, Footer
Data types:
- Header --> IndexHeader
- LuceneVersion --> Which Lucene code Version was used for this commit, written as three vInt: major, minor, bugfix
- MinSegmentLuceneVersion --> Lucene code Version of the oldest segment, written as three vInt: major, minor, bugfix; this is only written only if there's at least one segment
- NameCounter, SegCount, DeletionCount --> Int32
- Generation, Version, DelGen, Checksum, FieldInfosGen, DocValuesGen --> Int64
- HasSegID --> Int8
- SegID --> Int8^ID_LENGTH
- SegName, SegCodec --> String
- CommitUserData --> Map<String,String>
- UpdatesFiles --> Map<Int32, Set<String>>
- Footer --> CodecFooter
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.
- HasSegID is nonzero if the segment has an identifier. Otherwise, when it is 0 the identifier is null and no SegID is written. Null only happens for Lucene 4.x segments referenced in commits.
- SegID is the identifier of the Codec that encoded this segment.
- CommitUserData stores an optional user-supplied opaque Map<String,String> that was passed to IndexWriter.setCommitData(java.util.Map).
- 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 .
- DocValuesGen is the generation count of the updatable DocValues. If this is -1, there are no updates to DocValues in that segment. Anything above zero means there are updates to DocValues stored by DocValuesFormat.
- UpdatesFiles stores the set of files that were updated in that segment per field.
WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`SegmentInfos.FindSegmentsFile<T>` Utility class for executing code that needs to do something with the current segments file.

Field Summary

Fields
Modifier and Type	Field and Description
`int`	`counter` Used to name new segments.
`Map<String,String>`	`userData` Opaque Map<String, String> that user can specify during IndexWriter.commit
`long`	`version` Counts how often the index has been changed.
`static int`	`VERSION_40` The file format version for the segments_N codec header, up to 4.5.
`static int`	`VERSION_46` The file format version for the segments_N codec header, since 4.6+.
`static int`	`VERSION_48` The file format version for the segments_N codec header, since 4.8+
`static int`	`VERSION_49` The file format version for the segments_N codec header, since 4.9+
`static int`	`VERSION_50` The file format version for the segments_N codec header, since 5.0+
`static int`	`VERSION_51` The file format version for the segments_N codec header, since 5.1+
`static int`	`VERSION_53` Adds the `Version` that committed this segments_N file, as well as the `Version` of the oldest segment, since 5.3+

Constructor Summary

Constructors
Constructor and Description

SegmentInfos()
Sole constructor.

Constructors
Constructor and Description
`SegmentInfos()` Sole constructor.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`add(SegmentCommitInfo si)` Appends the provided `SegmentCommitInfo`.
`void`	`addAll(Iterable<SegmentCommitInfo> sis)` Appends the provided `SegmentCommitInfo`s.
`List<SegmentCommitInfo>`	`asList()` Returns all contained segments as an unmodifiable `List` view.
`void`	`changed()` Call this before committing if changes have been made to the segments.
`void`	`clear()` Clear all `SegmentCommitInfo`s.
`SegmentInfos`	`clone()` Returns a copy of this instance, also copying each SegmentInfo.
`Collection<String>`	`files(boolean includeSegmentsFile)` Returns all file names referenced by SegmentInfo.
`Collection<String>`	`files(Directory dir, boolean includeSegmentsFile)` Deprecated. Use `files(boolean)` instead.
`static long`	`generationFromSegmentsFileName(String fileName)` Parse the generation off the segments file name and return it.
`Version`	`getCommitLuceneVersion()` Returns which Lucene `Version` wrote this commit, or null if the version this index was written with did not directly record the version.
`long`	`getGeneration()` Returns current generation.
`byte[]`	`getId()` Since Lucene 5.0, every commit (segments_N) writes a unique id.
`static PrintStream`	`getInfoStream()` Returns `infoStream`.
`static long`	`getLastCommitGeneration(Directory directory)` Get the generation of the most recent commit to the index in this directory (N in the segments_N file).
`static long`	`getLastCommitGeneration(String[] files)` Get the generation of the most recent commit to the list of index files (N in the segments_N file).
`static String`	`getLastCommitSegmentsFileName(Directory directory)` Get the filename of the segments_N file for the most recent commit to the index in this Directory.
`static String`	`getLastCommitSegmentsFileName(String[] files)` Get the filename of the segments_N file for the most recent commit in the list of index files.
`long`	`getLastGeneration()` Returns last succesfully read or written generation.
`Version`	`getMinSegmentLuceneVersion()` Returns the version of the oldest segment, or null if there are no segments.
`String`	`getSegmentsFileName()` Get the segments_N filename in use by this segment infos.
`Map<String,String>`	`getUserData()` Return `userData` saved with this commit.
`long`	`getVersion()` version number when this SegmentInfos was generated.
`SegmentCommitInfo`	`info(int i)` Returns `SegmentCommitInfo` at the provided index.
`Iterator<SegmentCommitInfo>`	`iterator()` Returns an unmodifiable `Iterator` of contained segments in order.
`static SegmentInfos`	`readCommit(Directory directory, String segmentFileName)` Read a particular segmentFileName.
`static SegmentInfos`	`readLatestCommit(Directory directory)` Find the latest commit (`segments_N file`) and load all `SegmentCommitInfo`s.
`void`	`remove(SegmentCommitInfo si)` Remove the provided `SegmentCommitInfo`.
`static void`	`setInfoStream(PrintStream infoStream)` If non-null, information about retries when loading the segments file will be printed to this.
`int`	`size()` Returns number of `SegmentCommitInfo`s.
`String`	`toString()` Returns readable description of this segment.
`String`	`toString(Directory dir)` Deprecated. Use `toString()` instead.
`int`	`totalMaxDoc()` Returns sum of all segment's maxDocs.

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - VERSION_40
```
public static final int VERSION_40
```
    The file format version for the segments_N codec header, up to 4.5.
    
    See Also:
    Constant Field Values
  - VERSION_46
```
public static final int VERSION_46
```
    The file format version for the segments_N codec header, since 4.6+.
    
    See Also:
    Constant Field Values
  - VERSION_48
```
public static final int VERSION_48
```
    The file format version for the segments_N codec header, since 4.8+
    
    See Also:
    Constant Field Values
  - VERSION_49
```
public static final int VERSION_49
```
    The file format version for the segments_N codec header, since 4.9+
    
    See Also:
    Constant Field Values
  - VERSION_50
```
public static final int VERSION_50
```
    The file format version for the segments_N codec header, since 5.0+
    
    See Also:
    Constant Field Values
  - VERSION_51
```
public static final int VERSION_51
```
    The file format version for the segments_N codec header, since 5.1+
    
    See Also:
    Constant Field Values
  - VERSION_53
```
public static final int VERSION_53
```
    Adds the Version that committed this segments_N file, as well as the Version of the oldest segment, since 5.3+
    
    See Also:
    Constant Field Values
  - counter
```
public int counter
```
    Used to name new segments.
  - version
```
public long version
```
    Counts how often the index has been changed.
  - userData
```
public Map<String,String> userData
```
    Opaque Map<String, String> that user can specify during IndexWriter.commit
- Constructor Detail
  - SegmentInfos
```
public SegmentInfos()
```
    Sole constructor. Typically you call this and then use or #readCommit(Directory,String) to populate each SegmentCommitInfo. Alternatively, you can add/remove your own SegmentCommitInfos.
- Method Detail
  - info
```
public SegmentCommitInfo info(int i)
```
    Returns SegmentCommitInfo at the provided index.
  - getLastCommitGeneration
```
public static long getLastCommitGeneration(String[] files)
```
    Get the generation of the most recent commit to the list of index files (N in the segments_N file).
    
    Parameters:
    files - -- array of file names to check
  - getLastCommitGeneration
```
public static long getLastCommitGeneration(Directory directory)
                                    throws IOException
```
    Get the generation of the most recent commit to the index in this directory (N in the segments_N file).
    
    Parameters:
    directory - -- directory to search for the latest segments_N file
    
    Throws:
    
    IOException
  - getLastCommitSegmentsFileName
```
public static String getLastCommitSegmentsFileName(String[] files)
```
    Get the filename of the segments_N file for the most recent commit in the list of index files.
    
    Parameters:
    files - -- array of file names to check
  - getLastCommitSegmentsFileName
```
public static String getLastCommitSegmentsFileName(Directory directory)
                                            throws IOException
```
    Get the filename of the segments_N file for the most recent commit to the index in this Directory.
    
    Parameters:
    directory - -- directory to search for the latest segments_N file
    
    Throws:
    
    IOException
  - getSegmentsFileName
```
public String getSegmentsFileName()
```
    Get the segments_N filename in use by this segment infos.
  - generationFromSegmentsFileName
```
public static long generationFromSegmentsFileName(String fileName)
```
    Parse the generation off the segments file name and return it.
  - getId
```
public byte[] getId()
```
    Since Lucene 5.0, every commit (segments_N) writes a unique id. This will return that id, or null if this commit was prior to 5.0.
  - readCommit
```
public static final SegmentInfos readCommit(Directory directory,
                      String segmentFileName)
                                     throws IOException
```
    Read a particular segmentFileName. Note that this may throw an IOException if a commit is in process.
    
    Parameters:
    directory - -- directory containing the segments file
    segmentFileName - -- segment file to load
    
    Throws:
    
    CorruptIndexException - if the index is corrupt
    
    IOException - if there is a low-level IO error
  - readLatestCommit
```
public static final SegmentInfos readLatestCommit(Directory directory)
                                           throws IOException
```
    Find the latest commit (segments_N file) and load all SegmentCommitInfos.
    
    Throws:
    
    IOException
  - clone
```
public SegmentInfos clone()
```
    Returns a copy of this instance, also copying each SegmentInfo.
    
    Overrides:
    
    clone in class Object
  - getVersion
```
public long getVersion()
```
    version number when this SegmentInfos was generated.
  - getGeneration
```
public long getGeneration()
```
    Returns current generation.
  - getLastGeneration
```
public long getLastGeneration()
```
    Returns last succesfully read or written generation.
  - setInfoStream
```
public static void setInfoStream(PrintStream infoStream)
```
    If non-null, information about retries when loading the segments file will be printed to this.
  - getInfoStream
```
public static PrintStream getInfoStream()
```
    Returns infoStream.
    
    See Also:
    setInfoStream(java.io.PrintStream)
  - files
```
@Deprecated
public final Collection<String> files(Directory dir,
                                  boolean includeSegmentsFile)
                               throws IOException
```
    Deprecated. Use files(boolean) instead.
    
    Returns all file names referenced by SegmentInfo.
    
    Throws:
    
    IOException
  - files
```
public Collection<String> files(boolean includeSegmentsFile)
                         throws IOException
```
    Returns all file names referenced by SegmentInfo. The returned collection is recomputed on each invocation.
    
    Throws:
    
    IOException
  - toString
```
@Deprecated
public String toString(Directory dir)
```
    Deprecated. Use toString() instead.
    
    Returns readable description of this segment.
  - toString
```
public String toString()
```
    Returns readable description of this segment.
    
    Overrides:
    
    toString in class Object
  - getUserData
```
public Map<String,String> getUserData()
```
    Return userData saved with this commit.
    
    See Also:
    IndexWriter.commit()
  - totalMaxDoc
```
public int totalMaxDoc()
```
    Returns sum of all segment's maxDocs. Note that this does not include deletions
  - changed
```
public void changed()
```
    Call this before committing if changes have been made to the segments.
  - iterator
```
public Iterator<SegmentCommitInfo> iterator()
```
    Returns an unmodifiable Iterator of contained segments in order.
    
    Specified by:
    
    iterator in interface Iterable<SegmentCommitInfo>
  - asList
```
public List<SegmentCommitInfo> asList()
```
    Returns all contained segments as an unmodifiable List view.
  - size
```
public int size()
```
    Returns number of SegmentCommitInfos.
  - add
```
public void add(SegmentCommitInfo si)
```
    Appends the provided SegmentCommitInfo.
  - addAll
```
public void addAll(Iterable<SegmentCommitInfo> sis)
```
    Appends the provided SegmentCommitInfos.
  - clear
```
public void clear()
```
    Clear all SegmentCommitInfos.
  - remove
```
public void remove(SegmentCommitInfo si)
```
    Remove the provided SegmentCommitInfo.
    WARNING: O(N) cost
  - getCommitLuceneVersion
```
public Version getCommitLuceneVersion()
```
    Returns which Lucene Version wrote this commit, or null if the version this index was written with did not directly record the version.
  - getMinSegmentLuceneVersion
```
public Version getMinSegmentLuceneVersion()
```
    Returns the version of the oldest segment, or null if there are no segments.

Class SegmentInfos

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

VERSION_40

VERSION_46

VERSION_48

VERSION_49

VERSION_50

VERSION_51

VERSION_53

counter

version

userData

Constructor Detail

SegmentInfos

Method Detail

info

getLastCommitGeneration

getLastCommitGeneration

getLastCommitSegmentsFileName

getLastCommitSegmentsFileName

getSegmentsFileName

generationFromSegmentsFileName

getId

readCommit

readLatestCommit

clone

getVersion

getGeneration

getLastGeneration

setInfoStream

getInfoStream

files

files

toString

toString

getUserData

totalMaxDoc

changed

iterator

asList

size

add

addAll

clear

remove

getCommitLuceneVersion

getMinSegmentLuceneVersion