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java.lang.Object org.apache.lucene.search.function.ValueSource org.apache.lucene.search.function.ReverseOrdFieldSource
public class ReverseOrdFieldSource
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(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 | |
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String |
field
|
Constructor Summary | |
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ReverseOrdFieldSource(String field)
Contructor for a certain field. |
Method Summary | |
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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 |
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toString |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Field Detail |
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public String field
Constructor Detail |
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public ReverseOrdFieldSource(String field)
field
- field whose values reverse order is used.Method Detail |
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public String description()
ValueSource
description
in class ValueSource
public DocValues getValues(IndexReader reader) throws IOException
ValueSource
getValues
in class ValueSource
reader
- the IndexReader used to read these values.
If any caching is involved, that caching would also be IndexReader based.
IOException
- for any error.public boolean equals(Object o)
ValueSource
ValueSourceQuery.equals(Object)
.
equals
in class ValueSource
Object.equals(Object)
public int hashCode()
ValueSource
ValueSourceQuery.hashCode()
.
hashCode
in class ValueSource
Object.hashCode()
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