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

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

Field Summary

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

EMPTY

Constructor Summary

Constructors

Constructor and Description
CompletionPostingsFormat() Used only by core Lucene at read-time via Service Provider instantiation

Method Summary

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

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()

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

Method Detail

delegatePostingsFormat

protected abstract PostingsFormat delegatePostingsFormat()

Concrete implementation should specify the delegating postings format

fieldsConsumer

public FieldsConsumer fieldsConsumer(SegmentWriteState state)
                              throws java.io.IOException

Description copied from class: PostingsFormat

Writes a new segment

Specified by:

fieldsConsumer in class PostingsFormat

Throws:

java.io.IOException

fieldsProducer

public FieldsProducer fieldsProducer(SegmentReadState state)
                              throws java.io.IOException

Description copied from class: PostingsFormat

Reads a segment. NOTE: by the time this call returns, it must hold open any files it will need to use; else, those files may be deleted. Additionally, required files may be deleted during the execution of this call before there is a chance to open them. Under these circumstances an IOException should be thrown by the implementation. IOExceptions are expected and will automatically cause a retry of the segment opening logic with the newly revised segments.

Specified by:

fieldsProducer in class PostingsFormat

Throws:

java.io.IOException