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org.apache.lucene.search.function
public class: ReverseOrdFieldSource [javadoc | source]
java.lang.Object
   org.apache.lucene.search.function.ValueSource
      org.apache.lucene.search.function.ReverseOrdFieldSource

All Implemented Interfaces:
    Serializable

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.

WARNING: The status of the search.function package is experimental. The APIs introduced here might change in the future and will not be supported anymore in such a case.

NOTE: with the switch in 2.9 to segment-based searching, if #getValues 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
public  String field     
Constructor:
 public ReverseOrdFieldSource(String field) 
    Contructor for a certain field.
    Parameters:
    field - field whose values reverse order is used.
Method from org.apache.lucene.search.function.ReverseOrdFieldSource Summary:
description,   equals,   getValues,   hashCode
Methods from org.apache.lucene.search.function.ValueSource:
description,   equals,   getValues,   hashCode,   toString
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from org.apache.lucene.search.function.ReverseOrdFieldSource Detail:
 public String description() 
 public boolean equals(Object o) 
 public DocValues getValues(IndexReader reader) throws IOException 
 public int hashCode()