org.apache.lucene.search

Class TermStatistics

java.lang.Object

org.apache.lucene.search.TermStatistics

public class TermStatistics
extends Object

Contains statistics for a specific term

This class holds statistics for this term across all documents for scoring purposes:

• docFreq: number of documents this term occurs in.
• totalTermFreq: number of tokens for this term.

The following conditions are always true:

• All statistics are positive integers: never zero or negative.
• docFreq <= totalTermFreq
• docFreq <= sumDocFreq of the collection
• totalTermFreq <= sumTotalTermFreq of the collection

Values may include statistics on deleted documents that have not yet been merged away.

Be careful when performing calculations on these values because they are represented as 64-bit integer values, you may need to cast to double for your use.

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

Constructor Summary

Constructors

Constructor and Description
TermStatistics(BytesRef term, long docFreq, long totalTermFreq) Creates statistics instance for a term.

Method Summary

Modifier and Type	Method and Description
long	docFreq() The number of documents this term occurs in.
BytesRef	term() The term text.
String	toString()
long	totalTermFreq() The total number of occurrences of this term.

Methods inherited from class java.lang.Object

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

Constructor Detail

TermStatistics

public TermStatistics(BytesRef term,
                      long docFreq,
                      long totalTermFreq)

Creates statistics instance for a term.

Parameters:

term - Term bytes

docFreq - number of documents containing the term in the collection.

totalTermFreq - number of occurrences of the term in the collection.

Throws:

NullPointerException - if term is null.

IllegalArgumentException - if docFreq is negative or zero.

IllegalArgumentException - if totalTermFreq is less than docFreq.

Method Detail

term

public final BytesRef term()

The term text.

This value is never null.

Returns:

term's text, not null

docFreq

public final long docFreq()

The number of documents this term occurs in.

This is the document-frequency for the term: the count of documents where the term appears at least one time.

This value is always a positive number, and never exceeds totalTermFreq. It also cannot exceed CollectionStatistics.sumDocFreq().

Returns:

document frequency, in the range [1 .. totalTermFreq()]

See Also:

TermsEnum.docFreq()

totalTermFreq

public final long totalTermFreq()

The total number of occurrences of this term.

This is the token count for the term: the number of times it appears in the field across all documents.

This value is always a positive number, always at least docFreq(), and never exceeds CollectionStatistics.sumTotalTermFreq().

Returns:

number of occurrences, in the range [docFreq() .. CollectionStatistics.sumTotalTermFreq()]

See Also:

TermsEnum.totalTermFreq()

toString

public String toString()

Overrides:

toString in class Object