org.apache.lucene.search.function

Class ReverseOrdFieldSource

java.lang.Object

org.apache.lucene.search.function.ValueSource

org.apache.lucene.search.function.ReverseOrdFieldSource

All Implemented Interfaces:

Serializable

public class ReverseOrdFieldSource
extends ValueSource

Expert: obtains the ordinal of the field value from the default Lucene FieldCache using getStringIndex() and reverses the order.

The native lucene index order is used to assign an ordinal value for each field value.

Field values (terms) are lexicographically ordered by unicode value, and numbered starting at 1.
Example of reverse ordinal (rord):
If there were only three field values: "apple","banana","pear"
then rord("apple")=3, rord("banana")=2, ord("pear")=1

WARNING: rord() depends on the position in an index and can thus change when other documents are inserted or deleted, or if a MultiSearcher is used.

See Also:

Serialized Form

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

NOTE: with the switch in 2.9 to segment-based searching, if getValues(org.apache.lucene.index.IndexReader) is invoked with a composite (multi-segment) reader, this can easily cause double RAM usage for the values in the FieldCache. It's best to switch your application to pass only atomic (single segment) readers to this API.

Field Summary

Fields

Modifier and Type	Field and Description
String	field

Constructor Summary

Constructors

Constructor and Description
ReverseOrdFieldSource(String field) Contructor for a certain field.

Method Summary

Methods

Modifier and Type	Method and Description
String	description() description of field, used in explain()
boolean	equals(Object o) Needed for possible caching of query results - used by ValueSourceQuery.equals(Object).
DocValues	getValues(IndexReader reader) Return the DocValues used by the function query.
int	hashCode() Needed for possible caching of query results - used by ValueSourceQuery.hashCode().

Methods inherited from class org.apache.lucene.search.function.ValueSource

toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

field

public String field

Constructor Detail

ReverseOrdFieldSource

public ReverseOrdFieldSource(String field)

Contructor for a certain field.

Parameters:

field - field whose values reverse order is used.

Method Detail

description

public String description()

Description copied from class: ValueSource

description of field, used in explain()

Specified by:

description in class ValueSource

getValues

public DocValues getValues(IndexReader reader)
                    throws IOException

Description copied from class: ValueSource

Return the DocValues used by the function query.

Specified by:

getValues in class ValueSource

Parameters:

reader - the IndexReader used to read these values. If any caching is involved, that caching would also be IndexReader based.

Throws:

IOException - for any error.

equals

public boolean equals(Object o)

Description copied from class: ValueSource

Needed for possible caching of query results - used by ValueSourceQuery.equals(Object).

Specified by:

equals in class ValueSource

See Also:

Object.equals(Object)

hashCode

public int hashCode()

Description copied from class: ValueSource

Needed for possible caching of query results - used by ValueSourceQuery.hashCode().

Specified by:

hashCode in class ValueSource

See Also:

Object.hashCode()