Package org.apache.lucene.index

Code to maintain and access indices.

See: Description

Package org.apache.lucene.index Description

Code to maintain and access indices.

Table Of Contents

  1. Postings APIs
  2. Index Statistics

Postings APIs


Fields is the initial entry point into the postings APIs, this can be obtained in several ways:

// access indexed fields for an index segment
Fields fields = reader.fields();
// access term vector fields for a specified document
Fields fields = reader.getTermVectors(docid);
Fields implements Java's Iterable interface, so its easy to enumerate the list of fields:
// enumerate list of fields
for (String field : fields) {
  // access the terms for this field
  Terms terms = fields.terms(field);


Terms represents the collection of terms within a field, exposes some metadata and statistics, and an API for enumeration.

// metadata about the field
System.out.println("positions? " + terms.hasPositions());
System.out.println("offsets? " + terms.hasOffsets());
System.out.println("payloads? " + terms.hasPayloads());
// iterate through terms
TermsEnum termsEnum = terms.iterator(null);
BytesRef term = null;
while ((term = != null) {
TermsEnum provides an iterator over the list of terms within a field, some statistics about the term, and methods to access the term's documents and positions.
// seek to a specific term
boolean found = termsEnum.seekExact(new BytesRef("foobar"), true);
if (found) {
  // get the document frequency
  // enumerate through documents
  DocsEnum docs =, null);
  // enumerate through documents and positions
  DocsAndPositionsEnum docsAndPositions = termsEnum.docsAndPositions(null, null);


DocsEnum is an extension of DocIdSetIteratorthat iterates over the list of documents for a term, along with the term frequency within that document.

int docid;
while ((docid = docsEnum.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {


DocsAndPositionsEnum is an extension of DocsEnum that additionally allows iteration of the positions a term occurred within the document, and any additional per-position information (offsets and payload)

int docid;
while ((docid = docsAndPositionsEnum.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
  int freq = docsAndPositionsEnum.freq();
  for (int i = 0; i < freq; i++) {

Index Statistics

Term statistics

Field statistics

Segment statistics

Document statistics

Document statistics are available during the indexing process for an indexed field: typically a Similarity implementation will store some of these values (possibly in a lossy way), into the normalization value for the document in its Similarity.computeNorm(org.apache.lucene.index.FieldInvertState, org.apache.lucene.index.Norm) method.

Additional user-supplied statistics can be added to the document as DocValues fields and accessed via AtomicReader.docValues(java.lang.String).

Copyright © 2000-2012 Apache Software Foundation. All Rights Reserved.