org.apache.lucene.search
Class IndexSearcher

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

All Implemented Interfaces:

Searchable

public class IndexSearcher
extends Searcher

Implements search over a single IndexReader.

Applications usually need only call the inherited Searcher.search(Query,int) or Searcher.search(Query,Filter,int) methods. For performance reasons it is recommended to open only one IndexSearcher and use it for all of your searches.

Note that you can only access the deprecated Hits from an IndexSearcher as long as it is not yet closed, otherwise an IOException will be thrown.

NOTE: IndexSearcher instances are completely thread safe, meaning multiple threads can call any of its methods, concurrently. If your application requires external synchronization, you should not synchronize on the IndexSearcher instance; use your own (non-Lucene) objects instead.

Constructor Summary

IndexSearcher(Directory directory)
Deprecated. Use IndexSearcher(Directory, boolean) instead

IndexSearcher(Directory path, boolean readOnly)
Creates a searcher searching the index in the named directory.

IndexSearcher(IndexReader r)
Creates a searcher searching the provided index.

IndexSearcher(String path)
Deprecated. Use IndexSearcher(Directory, boolean) instead

IndexSearcher(String path, boolean readOnly)
Deprecated. Use IndexSearcher(Directory, boolean) instead

Method Summary

void	close() Note that the underlying IndexReader is not closed, if IndexSearcher was constructed with IndexSearcher(IndexReader r).
Document	doc(int i) Returns the stored fields of document i.
Document	doc(int i, FieldSelector fieldSelector) Get the Document at the nth position.
int	docFreq(Term term) Expert: Returns the number of documents containing term.
Explanation	explain(Weight weight, int doc) Expert: low-level implementation method Returns an Explanation that describes how doc scored against weight.
protected void	gatherSubReaders(List allSubReaders, IndexReader r)
IndexReader	getIndexReader() Return the IndexReader this searches.
int	maxDoc() Expert: Returns one greater than the largest possible document number.
Query	rewrite(Query original) Expert: called to re-write queries into primitive queries.
void	search(Weight weight, Filter filter, Collector collector) Lower-level search API.
TopDocs	search(Weight weight, Filter filter, int nDocs) Expert: Low-level search implementation.
TopFieldDocs	search(Weight weight, Filter filter, int nDocs, Sort sort) Expert: Low-level search implementation with arbitrary sorting.
TopFieldDocs	search(Weight weight, Filter filter, int nDocs, Sort sort, boolean fillFields) Just like search(Weight, Filter, int, Sort), but you choose whether or not the fields in the returned FieldDoc instances should be set by specifying fillFields.
void	setDefaultFieldSortScoring(boolean doTrackScores, boolean doMaxScore) By default, no scores are computed when sorting by field (using Searcher.search(Query,Filter,int,Sort)).

Methods inherited from class org.apache.lucene.search.Searcher

createWeight, docFreqs, explain, getSimilarity, search, search, search, search, search, search, search, search, search, search, search, search, setSimilarity

Methods inherited from class java.lang.Object

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

Constructor Detail

IndexSearcher

public IndexSearcher(String path)
              throws CorruptIndexException,
                     IOException

Deprecated. Use IndexSearcher(Directory, boolean) instead

Creates a searcher searching the index in the named directory.

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

IndexSearcher

public IndexSearcher(String path,
                     boolean readOnly)
              throws CorruptIndexException,
                     IOException

Deprecated. Use IndexSearcher(Directory, boolean) instead

Creates a searcher searching the index in the named directory. You should pass readOnly=true, since it gives much better concurrent performance, unless you intend to do write operations (delete documents or change norms) with the underlying IndexReader.

Parameters:

path - directory where IndexReader will be opened

readOnly - if true, the underlying IndexReader will be opened readOnly

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

IndexSearcher

public IndexSearcher(Directory directory)
              throws CorruptIndexException,
                     IOException

Deprecated. Use IndexSearcher(Directory, boolean) instead

Creates a searcher searching the index in the provided directory.

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

IndexSearcher

public IndexSearcher(Directory path,
                     boolean readOnly)
              throws CorruptIndexException,
                     IOException

Creates a searcher searching the index in the named directory. You should pass readOnly=true, since it gives much better concurrent performance, unless you intend to do write operations (delete documents or change norms) with the underlying IndexReader.

Parameters:

path - directory where IndexReader will be opened

readOnly - if true, the underlying IndexReader will be opened readOnly

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

IndexSearcher

public IndexSearcher(IndexReader r)

Creates a searcher searching the provided index.

Method Detail

gatherSubReaders

protected void gatherSubReaders(List allSubReaders,
                                IndexReader r)

getIndexReader

public IndexReader getIndexReader()

Return the IndexReader this searches.

close

public void close()
           throws IOException

Note that the underlying IndexReader is not closed, if IndexSearcher was constructed with IndexSearcher(IndexReader r). If the IndexReader was supplied implicitly by specifying a directory, then the IndexReader gets closed.

Specified by:

close in interface Searchable

Specified by:

close in class Searcher

Throws:

IOException

docFreq

public 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

Specified by:

docFreq in class Searcher

Throws:

IOException

See Also:

IndexReader.docFreq(Term)

doc

public 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

Specified by:

doc in class Searcher

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

See Also:

IndexReader.document(int)

doc

public Document doc(int i,
                    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.

Parameters:

i - 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

maxDoc

public 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

Specified by:

maxDoc in class Searcher

Throws:

IOException

See Also:

IndexReader.maxDoc()

search

public TopDocs search(Weight weight,
                      Filter filter,
                      int nDocs)
               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 Searcher.search(Query) or Searcher.search(Query,Filter) instead.

Specified by:

search in interface Searchable

Specified by:

search in class Searcher

Throws:

IOException

search

public TopFieldDocs search(Weight weight,
                           Filter filter,
                           int nDocs,
                           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 Searcher.search(Query,Filter,int,Sort) instead.

Specified by:

search in interface Searchable

Specified by:

search in class Searcher

Throws:

IOException

search

public TopFieldDocs search(Weight weight,
                           Filter filter,
                           int nDocs,
                           Sort sort,
                           boolean fillFields)
                    throws IOException

Just like search(Weight, Filter, int, Sort), but you choose whether or not the fields in the returned FieldDoc instances should be set by specifying fillFields.

NOTE: this does not compute scores by default. If you need scores, create a TopFieldCollector instance by calling TopFieldCollector.create(org.apache.lucene.search.Sort, int, boolean, boolean, boolean, boolean) and then pass that to search(Weight, Filter, Collector).

Throws:

IOException

search

public void search(Weight weight,
                   Filter filter,
                   Collector collector)
            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 (Searcher.search(Query)) is usually more efficient, as it skips non-high-scoring hits.

Specified by:

search in interface Searchable

Specified by:

search in class Searcher

Parameters:

weight - to match documents

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

collector - to receive hits

Throws:

IOException

rewrite

public Query rewrite(Query original)
              throws IOException

Description copied from interface: Searchable

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

Specified by:

rewrite in interface Searchable

Specified by:

rewrite in class Searcher

Throws:

IOException

explain

public 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 Searcher.explain(Query, int).

Specified by:

explain in interface Searchable

Specified by:

explain in class Searcher

Throws:

IOException

setDefaultFieldSortScoring

public void setDefaultFieldSortScoring(boolean doTrackScores,
                                       boolean doMaxScore)

By default, no scores are computed when sorting by field (using Searcher.search(Query,Filter,int,Sort)). You can change that, per IndexSearcher instance, by calling this method. Note that this will incur a CPU cost.

Parameters:

doTrackScores - If true, then scores are returned for every matching document in TopFieldDocs.

doMaxScore - If true, then the max score for all matching docs is computed.