Package org.apache.lucene.index

Class DocTermOrds

java.lang.Object

org.apache.lucene.index.DocTermOrds

public class DocTermOrds
extends Object

This class enables fast access to multiple term ords for a specified field across all docIDs. Like FieldCache, it uninverts the index and holds a packed data structure in RAM to enable fast access. Unlike FieldCache, it can handle multi-valued fields, and, it does not hold the term bytes in RAM. Rather, you must obtain a TermsEnum from the getOrdTermsEnum(org.apache.lucene.index.AtomicReader) method, and then seek-by-ord to get the term's bytes. While normally term ords are type long, in this API they are int as the internal representation here cannot address more than MAX_INT unique terms. Also, typically this class is used on fields with relatively few unique terms vs the number of documents. In addition, there is an internal limit (16 MB) on how many bytes each chunk of documents may consume. If you trip this limit you'll hit an IllegalStateException. Deleted documents are skipped during uninversion, and if you look them up you'll get 0 ords. The returned per-document ords do not retain their original order in the document. Instead they are returned in sorted (by ord, ie term's BytesRef comparator) order. They are also de-dup'd (ie if doc has same term more than once in this field, you'll only get that ord back once). This class tests whether the provided reader is able to retrieve terms by ord (ie, it's single segment, and it uses an ord-capable terms index). If not, this class will create its own term index internally, allowing to create a wrapped TermsEnum that can handle ord. The getOrdTermsEnum(org.apache.lucene.index.AtomicReader) method then provides this wrapped enum, if necessary. The RAM consumption of this class can be high!

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_INDEX_INTERVAL_BITS	Every 128th term is indexed, by default.

Constructor Summary

Constructors

Constructor	Description
DocTermOrds(AtomicReader reader, Bits liveDocs, String field)	Inverts all terms
DocTermOrds(AtomicReader reader, Bits liveDocs, String field, BytesRef termPrefix)	Inverts only terms starting w/ prefix
DocTermOrds(AtomicReader reader, Bits liveDocs, String field, BytesRef termPrefix, int maxTermDocFreq)	Inverts only terms starting w/ prefix, and only terms whose docFreq (not taking deletions into account) is invalid input: '<'= maxTermDocFreq
DocTermOrds(AtomicReader reader, Bits liveDocs, String field, BytesRef termPrefix, int maxTermDocFreq, int indexIntervalBits)	Inverts only terms starting w/ prefix, and only terms whose docFreq (not taking deletions into account) is invalid input: '<'= maxTermDocFreq, with a custom indexing interval (default is every 128nd term).

Method Summary

Modifier and Type	Method	Description
TermsEnum	getOrdTermsEnum(AtomicReader reader)	Returns a TermsEnum that implements ord.
boolean	isEmpty()	Returns true if no terms were indexed.
SortedSetDocValues	iterator(AtomicReader reader)	Returns a SortedSetDocValues view of this instance
BytesRef	lookupTerm(TermsEnum termsEnum, int ord)	Returns the term (BytesRef) corresponding to the provided ordinal.
int	numTerms()	Returns the number of terms in this field
long	ramUsedInBytes()	Returns total bytes used.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_INDEX_INTERVAL_BITS

public static final int DEFAULT_INDEX_INTERVAL_BITS

Every 128th term is indexed, by default.

See Also:

• Constant Field Values

Constructor Details

DocTermOrds

public DocTermOrds(AtomicReader reader,
 Bits liveDocs,
 String field)
            throws IOException

Inverts all terms

Throws:

IOException

DocTermOrds

public DocTermOrds(AtomicReader reader,
 Bits liveDocs,
 String field,
 BytesRef termPrefix)
            throws IOException

Inverts only terms starting w/ prefix

Throws:

IOException

DocTermOrds

public DocTermOrds(AtomicReader reader,
 Bits liveDocs,
 String field,
 BytesRef termPrefix,
 int maxTermDocFreq)
            throws IOException

Inverts only terms starting w/ prefix, and only terms whose docFreq (not taking deletions into account) is invalid input: '<'= maxTermDocFreq

Throws:

IOException

DocTermOrds

public DocTermOrds(AtomicReader reader,
 Bits liveDocs,
 String field,
 BytesRef termPrefix,
 int maxTermDocFreq,
 int indexIntervalBits)
            throws IOException

Inverts only terms starting w/ prefix, and only terms whose docFreq (not taking deletions into account) is invalid input: '<'= maxTermDocFreq, with a custom indexing interval (default is every 128nd term).

Throws:

IOException

Method Details

ramUsedInBytes

public long ramUsedInBytes()

Returns total bytes used.

getOrdTermsEnum

public TermsEnum getOrdTermsEnum(AtomicReader reader)
                          throws IOException

Returns a TermsEnum that implements ord. If the provided reader supports ord, we just return its TermsEnum; if it does not, we build a "private" terms index internally (WARNING: consumes RAM) and use that index to implement ord. This also enables ord on top of a composite reader. The returned TermsEnum is unpositioned. This returns null if there are no terms.

NOTE: you must pass the same reader that was used when creating this class

Throws:

IOException

numTerms

public int numTerms()

Returns the number of terms in this field

isEmpty

public boolean isEmpty()

Returns true if no terms were indexed.

lookupTerm

public BytesRef lookupTerm(TermsEnum termsEnum,
 int ord)
                    throws IOException

Returns the term (BytesRef) corresponding to the provided ordinal.

Throws:

IOException

iterator

public SortedSetDocValues iterator(AtomicReader reader)
                            throws IOException

Returns a SortedSetDocValues view of this instance

Throws:

IOException