Package org.apache.lucene.search

# Class BoostQuery

java.lang.Object
org.apache.lucene.search.Query
org.apache.lucene.search.BoostQuery

public final class BoostQuery extends Query
A `Query` wrapper that allows to give a boost to the wrapped query. Boost values that are less than one will give less importance to this query compared to other ones while values that are greater than one will give more importance to the scores returned by this query.

More complex boosts can be applied by using FunctionScoreQuery in the lucene-queries module

## Constructor Summary

Constructors
Constructor
Description
`BoostQuery(Query query, float boost)`
Sole constructor: wrap `query` in such a way that the produced scores will be boosted by `boost`.

## Method Summary

Modifier and Type
Method
Description
`Weight`
`createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost)`
Expert: Constructs an appropriate Weight implementation for this query.
`boolean`
`equals(Object other)`
Override and implement query instance equivalence properly in a subclass.
`float`
`getBoost()`
Return the applied boost.
`Query`
`getQuery()`
Return the wrapped `Query`.
`int`
`hashCode()`
Override and implement query hash code properly in a subclass.
`Query`
`rewrite(IndexSearcher indexSearcher)`
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.
`void`
`visit(QueryVisitor visitor)`
Recurse through the query tree, visiting any child queries.

### Methods inherited from class org.apache.lucene.search.Query

`classHash, sameClassAs, toString`

### Methods inherited from class java.lang.Object

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

## Constructor Details

### BoostQuery

public BoostQuery(Query query, float boost)
Sole constructor: wrap `query` in such a way that the produced scores will be boosted by `boost`.

## Method Details

### getQuery

public Query getQuery()
Return the wrapped `Query`.

### getBoost

public float getBoost()
Return the applied boost.

### equals

public boolean equals(Object other)
Description copied from class: `Query`
Override and implement query instance equivalence properly in a subclass. This is required so that `QueryCache` works properly.

Typically a query will be equal to another only if it's an instance of the same class and its document-filtering properties are identical to those of the other instance. Utility methods are provided for certain repetitive code.

Specified by:
  `equals` in class `Query`
See Also:
  - `Query.sameClassAs(Object)`
  - `Query.classHash()`

### hashCode

public int hashCode()
Description copied from class: `Query`
Override and implement query hash code properly in a subclass. This is required so that `QueryCache` works properly.

Specified by:
  `hashCode` in class `Query`
See Also:
  - `Query.equals(Object)`

### rewrite

public Query rewrite(IndexSearcher indexSearcher) 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.

Callers are expected to call `rewrite` multiple times if necessary, until the rewritten query is the same as the original query.

The rewrite process may be able to make use of IndexSearcher's executor and be executed in parallel if the executor is provided.

Overrides:
  `rewrite` in class `Query`
Throws:
  `IOException`
See Also:
  - `IndexSearcher.rewrite(Query)`

### visit

public void visit(QueryVisitor visitor)
Description copied from class: `Query`
Recurse through the query tree, visiting any child queries.

Specified by:
  `visit` in class `Query`
Parameters:
  `visitor` - a QueryVisitor to be called by each query in the tree

### 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.

Specified by:
  `toString` in class `Query`

### createWeight

public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException
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`
Parameters:
  `scoreMode` - How the produced scorers will be consumed.
  `boost` - The boost that is propagated by the parent queries.
Throws:
  `IOException`