Package org.apache.lucene.search.suggest.document

Class CompletionPostingsFormat

java.lang.Object

org.apache.lucene.codecs.PostingsFormat

org.apache.lucene.search.suggest.document.CompletionPostingsFormat

All Implemented Interfaces:

NamedSPILoader.NamedSPI

Direct Known Subclasses:

Completion50PostingsFormat, Completion84PostingsFormat, Completion90PostingsFormat

public abstract class CompletionPostingsFormat
extends PostingsFormat

A PostingsFormat which supports document suggestion based on indexed SuggestFields. Document suggestion is based on an weighted FST which map analyzed terms of a SuggestField to its surface form and document id.

Files:

• .lkp: Completion Dictionary
• .cmp: Completion Index

Completion Dictionary

The .lkp file contains an FST for each suggest field

• CompletionDict (.lkp) --> Header, FST^{NumSuggestFields}, Footer
• Header --> CodecHeader
• FST --> FST<Long, BytesRef>
• Footer --> CodecFooter

Notes:

• Header is a CodecHeader storing the version information for the Completion implementation.
• FST maps all analyzed forms to surface forms of a SuggestField

Completion Index

The .cmp file contains an index into the completion dictionary, so that it can be accessed randomly.

• CompletionIndex (.cmp) --> Header, NumSuggestFields, Entry^{NumSuggestFields}, Footer
• Header --> CodecHeader
• NumSuggestFields --> Uint32
• Entry --> FieldNumber, CompletionDictionaryOffset, MinWeight, MaxWeight, Type
• FieldNumber --> Uint32
• CompletionDictionaryOffset --> Uint64
• MinWeight --> Uint64
• MaxWeight --> Uint64
• Type --> Byte
• Footer --> CodecFooter

Notes:

• Header is a CodecHeader storing the version information for the Completion implementation.
• NumSuggestFields is the number of suggest fields indexed
• FieldNumber is the fields number from FieldInfos. (.fnm)
• CompletionDictionaryOffset is the file offset of a field's FST in CompletionDictionary (.lkp)
• MinWeight and MaxWeight are the global minimum and maximum weight for the field
• Type indicates if the suggester has context or not

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

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	CompletionPostingsFormat.FSTLoadMode	An enum that allows to control if suggester FSTs are loaded into memory or read off-heap

Field Summary

Fields inherited from class org.apache.lucene.codecs.PostingsFormat

EMPTY

Constructor Summary

Constructors

Constructor	Description
CompletionPostingsFormat(String name)	Used only by core Lucene at read-time via Service Provider instantiation
CompletionPostingsFormat(String name, CompletionPostingsFormat.FSTLoadMode fstLoadMode)	Creates a CompletionPostingsFormat that will use the provided fstLoadMode to determine if the completion FST should be loaded on or off heap.

Method Summary

Modifier and Type	Method	Description
protected abstract PostingsFormat	delegatePostingsFormat()	Concrete implementation should specify the delegating postings format
FieldsConsumer	fieldsConsumer(SegmentWriteState state)
FieldsProducer	fieldsProducer(SegmentReadState state)

Methods inherited from class org.apache.lucene.codecs.PostingsFormat

availablePostingsFormats, forName, getName, reloadPostingsFormats, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

CompletionPostingsFormat

public CompletionPostingsFormat(String name)

Used only by core Lucene at read-time via Service Provider instantiation

CompletionPostingsFormat

public CompletionPostingsFormat(String name,
                                CompletionPostingsFormat.FSTLoadMode fstLoadMode)

Creates a CompletionPostingsFormat that will use the provided fstLoadMode to determine if the completion FST should be loaded on or off heap.

Method Detail

delegatePostingsFormat

protected abstract PostingsFormat delegatePostingsFormat()

Concrete implementation should specify the delegating postings format

fieldsConsumer

public FieldsConsumer fieldsConsumer(SegmentWriteState state)
                              throws IOException

Specified by:

fieldsConsumer in class PostingsFormat

Throws:

IOException

fieldsProducer

public FieldsProducer fieldsProducer(SegmentReadState state)
                              throws IOException

Specified by:

fieldsProducer in class PostingsFormat

Throws:

IOException