org.apache.lucene.search
Class Searcher

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

All Implemented Interfaces:

Closeable, Searchable

Direct Known Subclasses:

IndexSearcher, MultiSearcher

public abstract class Searcher
extends Object
implements Searchable

An abstract base class for search implementations. Implements the main search methods.

Note that you can only access hits from a Searcher as long as it is not yet closed, otherwise an IOException will be thrown.

Constructor Summary

Searcher()

Method Summary

abstract void	close() Frees resources associated with this Searcher.
protected Weight	createWeight(Query query) creates a weight for query
abstract Document	doc(int i) Returns the stored fields of document i.
abstract Document	doc(int docid, FieldSelector fieldSelector) Get the Document at the nth position.
abstract int	docFreq(Term term) Expert: Returns the number of documents containing term.
int[]	docFreqs(Term[] terms) Expert: For each term in the terms array, calculates the number of documents containing term.
Explanation	explain(Query query, int doc) Returns an Explanation that describes how doc scored against query.
abstract Explanation	explain(Weight weight, int doc) Expert: low-level implementation method Returns an Explanation that describes how doc scored against weight.
Similarity	getSimilarity() Expert: Return the Similarity implementation used by this Searcher.
abstract int	maxDoc() Expert: Returns one greater than the largest possible document number.
abstract Query	rewrite(Query query) Expert: called to re-write queries into primitive queries.
void	search(Query query, Collector results) Lower-level search API.
void	search(Query query, Filter filter, Collector results) Lower-level search API.
TopDocs	search(Query query, Filter filter, int n) Finds the top n hits for query, applying filter if non-null.
TopFieldDocs	search(Query query, Filter filter, int n, Sort sort) Search implementation with arbitrary sorting.
TopDocs	search(Query query, int n) Finds the top n hits for query.
abstract void	search(Weight weight, Filter filter, Collector results) Lower-level search API.
abstract TopDocs	search(Weight weight, Filter filter, int n) Expert: Low-level search implementation.
abstract TopFieldDocs	search(Weight weight, Filter filter, int n, Sort sort) Expert: Low-level search implementation with arbitrary sorting.
void	setSimilarity(Similarity similarity) Expert: Set the Similarity implementation used by this Searcher.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Searcher

public Searcher()

Method Detail

search

public TopFieldDocs search(Query query,
                           Filter filter,
                           int n,
                           Sort sort)
                    throws IOException

Search implementation with arbitrary sorting. Finds the top n hits for query, applying filter if non-null, and sorting the hits by the criteria in sort.

NOTE: this does not compute scores by default; use IndexSearcher.setDefaultFieldSortScoring(boolean, boolean) to enable scoring.

Throws:

BooleanQuery.TooManyClauses

IOException

search

public void search(Query query,
                   Collector results)
            throws IOException

Lower-level search API.

Collector.collect(int) is called for every matching document.

Applications should only use this if they need all of the matching documents. The high-level search API (search(Query, int)) is usually more efficient, as it skips non-high-scoring hits.

Note: The score passed to this method is a raw score. In other words, the score will not necessarily be a float whose value is between 0 and 1.

Throws:

BooleanQuery.TooManyClauses

IOException

search

public void search(Query query,
                   Filter filter,
                   Collector results)
            throws IOException

Lower-level search API.

Collector.collect(int) is called for every matching document.
Collector-based access to remote indexes is discouraged.

Applications should only use this if they need all of the matching documents. The high-level search API (search(Query, Filter, int)) is usually more efficient, as it skips non-high-scoring hits.

Parameters:

query - to match documents

filter - if non-null, used to permit documents to be collected.

results - to receive hits

Throws:

BooleanQuery.TooManyClauses

IOException

search

public TopDocs search(Query query,
                      Filter filter,
                      int n)
               throws IOException

Finds the top n hits for query, applying filter if non-null.

Throws:

BooleanQuery.TooManyClauses

IOException

search

public TopDocs search(Query query,
                      int n)
               throws IOException

Finds the top n hits for query.

Throws:

BooleanQuery.TooManyClauses

IOException

explain

public Explanation explain(Query query,
                           int doc)
                    throws IOException

Returns an Explanation that describes how doc scored against query.

This is intended to be used in developing Similarity implementations, and, for good performance, should not be displayed with every hit. Computing an explanation is as expensive as executing the query over the entire index.

Throws:

IOException

setSimilarity

public void setSimilarity(Similarity similarity)

Expert: Set the Similarity implementation used by this Searcher.

See Also:

Similarity.setDefault(Similarity)

getSimilarity

public Similarity getSimilarity()

Expert: Return the Similarity implementation used by this Searcher.

This defaults to the current value of Similarity.getDefault().

createWeight

protected Weight createWeight(Query query)
                       throws IOException

creates a weight for query

Returns:

new weight

Throws:

IOException

docFreqs

public int[] docFreqs(Term[] terms)
               throws IOException

Description copied from interface: Searchable

Expert: For each term in the terms array, calculates the number of documents containing term. Returns an array with these document frequencies. Used to minimize number of remote calls.

Specified by:

docFreqs in interface Searchable

Throws:

IOException

search

public abstract void search(Weight weight,
                            Filter filter,
                            Collector results)
                     throws IOException

Description copied from interface: Searchable

Lower-level search API.

Collector.collect(int) is called for every document.
Collector-based access to remote indexes is discouraged.

Applications should only use this if they need all of the matching documents. The high-level search API (search(Query,int)) is usually more efficient, as it skips non-high-scoring hits.

Specified by:

search in interface Searchable

Parameters:

weight - to match documents

filter - if non-null, used to permit documents to be collected.

results - to receive hits

Throws:

IOException

close

public abstract void close()
                    throws IOException

Description copied from interface: Searchable

Frees resources associated with this Searcher. Be careful not to call this method while you are still using objects that reference this Searchable.

Specified by:

close in interface Closeable

Specified by:

close in interface Searchable

Throws:

IOException

docFreq

public abstract int docFreq(Term term)
                     throws IOException

Description copied from interface: Searchable

Expert: Returns the number of documents containing term.

Specified by:

docFreq in interface Searchable

Throws:

IOException

See Also:

IndexReader.docFreq(Term)

maxDoc

public abstract int maxDoc()
                    throws IOException

Description copied from interface: Searchable

Expert: Returns one greater than the largest possible document number.

Specified by:

maxDoc in interface Searchable

Throws:

IOException

See Also:

IndexReader.maxDoc()

search

public abstract TopDocs search(Weight weight,
                               Filter filter,
                               int n)
                        throws IOException

Description copied from interface: Searchable

Expert: Low-level search implementation. Finds the top n hits for query, applying filter if non-null.

Applications should usually call search(Query,int) or search(Query,Filter,int) instead.

Specified by:

search in interface Searchable

Throws:

IOException

doc

public abstract Document doc(int i)
                      throws CorruptIndexException,
                             IOException

Description copied from interface: Searchable

Returns the stored fields of document i.

Specified by:

doc in interface Searchable

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

See Also:

IndexReader.document(int)

doc

public abstract Document doc(int docid,
                             FieldSelector fieldSelector)
                      throws CorruptIndexException,
                             IOException

Description copied from interface: Searchable

Get the Document at the n^th position. The FieldSelector may be used to determine what Fields to load and how they should be loaded. NOTE: If the underlying Reader (more specifically, the underlying FieldsReader) is closed before the lazy Field is loaded an exception may be thrown. If you want the value of a lazy Field to be available after closing you must explicitly load it or fetch the Document again with a new loader.

Specified by:

doc in interface Searchable

Parameters:

docid - Get the document at the n^th position

fieldSelector - The FieldSelector to use to determine what Fields should be loaded on the Document. May be null, in which case all Fields will be loaded.

Returns:

The stored fields of the Document at the nth position

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

See Also:

IndexReader.document(int, FieldSelector), Fieldable, FieldSelector, SetBasedFieldSelector, LoadFirstFieldSelector

rewrite

public abstract Query rewrite(Query query)
                       throws IOException

Description copied from interface: Searchable

Expert: called to re-write queries into primitive queries.

Specified by:

rewrite in interface Searchable

Throws:

IOException

explain

public abstract Explanation explain(Weight weight,
                                    int doc)
                             throws IOException

Description copied from interface: Searchable

Expert: low-level implementation method Returns an Explanation that describes how doc scored against weight.

This is intended to be used in developing Similarity implementations, and, for good performance, should not be displayed with every hit. Computing an explanation is as expensive as executing the query over the entire index.

Applications should call explain(Query, int).

Specified by:

explain in interface Searchable

Throws:

IOException

search

public abstract TopFieldDocs search(Weight weight,
                                    Filter filter,
                                    int n,
                                    Sort sort)
                             throws IOException

Description copied from interface: Searchable

Expert: Low-level search implementation with arbitrary sorting. Finds the top n hits for query, applying filter if non-null, and sorting the hits by the criteria in sort.

Applications should usually call search(Query,Filter,int,Sort) instead.

Specified by:

search in interface Searchable

Throws:

IOException