Package org.apache.lucene.index

# Class SegmentInfo

java.lang.Object
org.apache.lucene.index.SegmentInfo

public final class SegmentInfo extends Object
Information about a segment such as its name, directory, and files related to the segment.

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

## Field Summary

Fields
Modifier and Type
Field
Description
`final Directory`
`dir`
Where this segment resides.
`final String`
`name`
Unique segment name in the directory.
`static final int`
`NO`
Used by some member fields to mean not present (e.g., norms, deletions).
`static final int`
`YES`
Used by some member fields to mean present (e.g., norms, deletions).

## Constructor Summary

Constructors
Constructor
Description
`SegmentInfo(Directory dir, Version version, Version minVersion, String name, int maxDoc, boolean isCompoundFile, boolean hasBlocks, Codec codec, Map<String,String> diagnostics, byte[] id, Map<String,String> attributes, Sort indexSort)`
Construct a new complete SegmentInfo instance from input.

## Method Summary

Modifier and Type
Method
Description
`void`
`addDiagnostics(Map<String,String> diagnostics)`
Adds or modifies this segment's diagnostics.
`void`
`addFile(String file)`
Add this file to the set of files written for this segment.
`void`
`addFiles(Collection<String> files)`
Add these files to the set of files written for this segment.
`boolean`
`equals(Object obj)`
We consider another SegmentInfo instance equal if it has the same dir and same name.
`Set<String>`
`files()`
Return all files referenced by this SegmentInfo.
`String`
`getAttribute(String key)`
Get a codec attribute value, or null if it does not exist
`Map<String,String>`
`getAttributes()`
Returns the internal codec attributes map.
`Codec`
`getCodec()`
Return `Codec` that wrote this segment.
`Map<String,String>`
`getDiagnostics()`
Returns diagnostics saved into the segment when it was written.
`boolean`
`getHasBlocks()`
Returns true if this segment contains documents written as blocks.
`byte[]`
`getId()`
Return the id that uniquely identifies this segment.
`Sort`
`getIndexSort()`
Return the sort order of this segment, or null if the index has no sort.
`Version`
`getMinVersion()`
Return the minimum Lucene version that contributed documents to this segment, or `null` if it is unknown.
`boolean`
`getUseCompoundFile()`
Returns true if this segment is stored as a compound file; else, false.
`Version`
`getVersion()`
Returns the version of the code which wrote the segment.
`int`
`hashCode()`
`int`
`maxDoc()`
Returns number of documents in this segment (deletions are not taken into account).
`String`
`putAttribute(String key, String value)`
Puts a codec attribute value.
`void`
`setCodec(Codec codec)`
Can only be called once.
`void`
`setFiles(Collection<String> files)`
Sets the files written for this segment.
`String`
`toString()`
`String`
`toString(int delCount)`
Used for debugging.

### Methods inherited from class java.lang.Object

`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

## Field Details

### NO

public static final int NO
Used by some member fields to mean not present (e.g., norms, deletions).

See Also:
  - Constant Field Values

### YES

public static final int YES
Used by some member fields to mean present (e.g., norms, deletions).

See Also:
  - Constant Field Values

### name

public final String name
Unique segment name in the directory.

### dir

public final Directory dir
Where this segment resides.

## Constructor Details

### SegmentInfo

public SegmentInfo(Directory dir, Version version, Version minVersion, String name, int maxDoc, boolean isCompoundFile, boolean hasBlocks, Codec codec, Map<String,String> diagnostics, byte[] id, Map<String,String> attributes, Sort indexSort)
Construct a new complete SegmentInfo instance from input.

Note: this is public only to allow access from the codecs package.

## Method Details

### addDiagnostics

public void addDiagnostics(Map<String,String> diagnostics)
Adds or modifies this segment's diagnostics.

Entries in the given map whose keys are not present in the current diagnostics are added. Otherwise, existing entries are modified with the given map's value.

Parameters:
  `diagnostics` - the additional diagnostics

### getDiagnostics

public Map<String,String> getDiagnostics()
Returns diagnostics saved into the segment when it was written. The map is immutable.

### getUseCompoundFile

public boolean getUseCompoundFile()
Returns true if this segment is stored as a compound file; else, false.

### getHasBlocks

public boolean getHasBlocks()
Returns true if this segment contains documents written as blocks.

See Also:
  - `LeafMetaData.hasBlocks()`

### setCodec

public void setCodec(Codec codec)
Can only be called once.

### getCodec

public Codec getCodec()
Return `Codec` that wrote this segment.

### maxDoc

public int maxDoc()
Returns number of documents in this segment (deletions are not taken into account).

### files

public Set<String> files()
Return all files referenced by this SegmentInfo.

### toString

public String toString()

Overrides:
  `toString` in class `Object`

### toString

public String toString(int delCount)
Used for debugging. Format may suddenly change.

Current format looks like `_a(3.1):c45/4:[sorter=<long: "timestamp">!]`, which means the segment's name is `_a`; it was created with Lucene 3.1 (or '?' if it's unknown); it's using compound file format (would be `C` if not compound); it has 45 documents; it has 4 deletions (this part is left off when there are no deletions); it is sorted by the timestamp field in descending order (this part is omitted for unsorted segments).

### equals

public boolean equals(Object obj)
We consider another SegmentInfo instance equal if it has the same dir and same name.

Overrides:
  `equals` in class `Object`

### hashCode

public int hashCode()

Overrides:
  `hashCode` in class `Object`

### getVersion

public Version getVersion()
Returns the version of the code which wrote the segment.

### getMinVersion

public Version getMinVersion()
Return the minimum Lucene version that contributed documents to this segment, or `null` if it is unknown.

### getId

public byte[] getId()
Return the id that uniquely identifies this segment.

### setFiles

public void setFiles(Collection<String> files)
Sets the files written for this segment.

### addFiles

public void addFiles(Collection<String> files)
Add these files to the set of files written for this segment.

### addFile

public void addFile(String file)
Add this file to the set of files written for this segment.

### getAttribute

public String getAttribute(String key)
Get a codec attribute value, or null if it does not exist

### putAttribute

public String putAttribute(String key, String value)
Puts a codec attribute value.

This is a key-value mapping for the field that the codec can use to store additional metadata, and will be available to the codec when reading the segment via `getAttribute(String)`

If a value already exists for the field, it will be replaced with the new value. This method make a copy on write for every attribute change.

### getAttributes

public Map<String,String> getAttributes()
Returns the internal codec attributes map.

Returns:
  internal codec attributes map.

### getIndexSort

public Sort getIndexSort()
Return the sort order of this segment, or null if the index has no sort.