Query (Lucene 2.4.1 API)
Keywords: org.apache.lucene.search.Query class

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## org.apache.lucene.search
Class Query

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

All Implemented Interfaces:
  Serializable, Cloneable

Direct Known Subclasses:
  BooleanQuery, ConstantScoreQuery, ConstantScoreRangeQuery, CustomScoreQuery, DisjunctionMaxQuery, FilteredQuery, MatchAllDocsQuery, MultiPhraseQuery, MultiTermQuery, PhraseQuery, PrefixQuery, RangeQuery, SpanQuery, TermQuery, ValueSourceQuery

    public abstract class Query

extends Object
implements Serializable, Cloneable

The abstract base class for queries.

Instantiable subclasses are:

- `TermQuery`
- `MultiTermQuery`
- `BooleanQuery`
- `WildcardQuery`
- `PhraseQuery`
- `PrefixQuery`
- `MultiPhraseQuery`
- `FuzzyQuery`
- `RangeQuery`
- `SpanQuery`

A parser for queries is contained in:

- `QueryParser`

See Also:
  Serialized Form

Constructor Summary
`Query()`

Method Summary
`Object` | `clone()` Returns a clone of this query.
`Query` | `combine(Query[] queries)` Expert: called when re-writing queries under MultiSearcher.
`protected Weight` | `createWeight(Searcher searcher)` Expert: Constructs an appropriate Weight implementation for this query.
`void` | `extractTerms(Set terms)` Expert: adds all terms occuring in this query to the terms set.
`float` | `getBoost()` Gets the boost for this clause.
`Similarity` | `getSimilarity(Searcher searcher)` Expert: Returns the Similarity implementation to be used for this query.
`static Query` | `mergeBooleanQueries(Query[] queries)` Expert: merges the clauses of a set of BooleanQuery's into a single BooleanQuery.
`Query` | `rewrite(IndexReader reader)` Expert: called to re-write queries into primitive queries.
`void` | `setBoost(float b)` Sets the boost for this query clause to `b`.
`String` | `toString()` Prints a query to a string.
`abstract String` | `toString(String field)` Prints a query to a string, with `field` assumed to be the default field and omitted.
`Weight` | `weight(Searcher searcher)` Expert: Constructs and initializes a Weight for a top-level query.

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

Constructor Detail

### Query

    public Query()

Method Detail

### setBoost

    public void setBoost(float b)

  Sets the boost for this query clause to `b`. Documents matching this clause will (in addition to the normal weightings) have their score multiplied by `b`.

### getBoost

    public float getBoost()

  Gets the boost for this clause. Documents matching this clause will (in addition to the normal weightings) have their score multiplied by `b`. The boost is 1.0 by default.

### toString

    public abstract String toString(String field)

  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.

### toString

    public String toString()

  Prints a query to a string.

  Overrides:
    `toString` in class `Object`

### createWeight

    protected Weight createWeight(Searcher searcher)
                           throws IOException

  Expert: Constructs an appropriate Weight implementation for this query.

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

  Throws:
    `IOException`

### weight

    public Weight weight(Searcher searcher)
                  throws IOException

  Expert: Constructs and initializes a Weight for a top-level query.

  Throws:
    `IOException`

### rewrite

    public Query rewrite(IndexReader reader)
                  throws IOException

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

  Throws:
    `IOException`

### combine

    public Query combine(Query[] queries)

  Expert: called when re-writing queries under MultiSearcher. Create a single query suitable for use by all subsearchers (in 1-1 correspondence with queries). This is an optimization of the OR of all queries. We handle the common optimization cases of equal queries and overlapping clauses of boolean OR queries (as generated by MultiTermQuery.rewrite() and RangeQuery.rewrite()). Be careful overriding this method as queries[0] determines which method will be called and is not necessarily of the same type as the other queries.

### extractTerms

    public void extractTerms(Set terms)

  Expert: adds all terms occuring in this query to the terms set. Only works if this query is in its `rewritten` form.

  Throws:
    `UnsupportedOperationException` - if this query is not yet rewritten

### mergeBooleanQueries

    public static Query mergeBooleanQueries(Query[] queries)

  Expert: merges the clauses of a set of BooleanQuery's into a single BooleanQuery.

  A utility for use by `combine(Query[])` implementations.

### getSimilarity

    public Similarity getSimilarity(Searcher searcher)

  Expert: Returns the Similarity implementation to be used for this query. Subclasses may override this method to specify their own Similarity implementation, perhaps one that delegates through that of the Searcher. By default the Searcher's Similarity implementation is returned.

### clone

    public Object clone()

  Returns a clone of this query.

  Overrides:
    `clone` in class `Object`

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