ValueSourceQuery (Lucene 3.6.2 API)
Keywords: org.apache.lucene.search.function.ValueSourceQuery class

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## org.apache.lucene.search.function
Class ValueSourceQuery

    java.lang.Object
      org.apache.lucene.search.Query
          org.apache.lucene.search.function.ValueSourceQuery

All Implemented Interfaces:
  Serializable, Cloneable

Direct Known Subclasses:
  FieldScoreQuery

    public class ValueSourceQuery

extends Query

Expert: A Query that sets the scores of document to the values obtained from a `ValueSource`.

This query provides a score for each and every undeleted document in the index.

The value source can be based on a (cached) value of an indexed field, but it can also be based on an external source, e.g. values read from an external database.

Score is set as: Score(doc,query) = query.getBoost()2 * valueSource(doc).

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

Constructor Summary
`ValueSourceQuery(ValueSource valSrc)` Create a value source query

Method Summary
`Weight` | `createWeight(Searcher searcher)` Expert: Constructs an appropriate Weight implementation for this query.
`boolean` | `equals(Object o)` Returns true if `o` is equal to this.
`void` | `extractTerms(Set<Term> terms)` Expert: adds all terms occurring in this query to the terms set.
`int` | `hashCode()` Returns a hash code value for this object.
`Query` | `rewrite(IndexReader reader)` Expert: called to re-write queries into primitive queries.
`String` | `toString(String field)` Prints a query to a string, with `field` assumed to be the default field and omitted.

Methods inherited from class org.apache.lucene.search.Query
`clone, combine, getBoost, getSimilarity, mergeBooleanQueries, setBoost, toString, weight`

Methods inherited from class java.lang.Object
`finalize, getClass, notify, notifyAll, wait, wait, wait`

Constructor Detail

### ValueSourceQuery

    public ValueSourceQuery(ValueSource valSrc)

  Create a value source query

  Parameters:
    `valSrc` - provides the values defines the function to be used for scoring

Method Detail

### rewrite

    public Query rewrite(IndexReader reader)
                  throws IOException

  Description copied from class: `Query`
  Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

  Overrides:
    `rewrite` in class `Query`
  Throws:
    `IOException`

### extractTerms

    public void extractTerms(Set<Term> terms)

  Description copied from class: `Query`
  Expert: adds all terms occurring in this query to the terms set. Only works if this query is in its `rewritten` form.

  Overrides:
    `extractTerms` in class `Query`

### createWeight

    public Weight createWeight(Searcher searcher)

  Description copied from class: `Query`
  Expert: Constructs an appropriate Weight implementation for this query.

  Only implemented by primitive queries, which re-write to themselves.

  Overrides:
    `createWeight` in class `Query`

### toString

    public String toString(String field)

  Description copied from class: `Query`
  Prints a query to a string, with `field` assumed to be the default field and omitted.

  The representation used is one that is supposed to be readable by `QueryParser`. However, there are the following limitations:

  - If the query was created by the parser, the printed representation may not be exactly what was parsed. For example, characters that need to be escaped will be represented without the required backslash.
  - Some of the more complicated queries (e.g. span queries) don't have a representation that can be parsed by QueryParser.

  Specified by:
    `toString` in class `Query`

### equals

    public boolean equals(Object o)

  Returns true if `o` is equal to this.

  Overrides:
    `equals` in class `Query`

### hashCode

    public int hashCode()

  Returns a hash code value for this object.

  Overrides:
    `hashCode` in class `Query`

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