org.apache.lucene.search
Class IndexSearcher

java.lang.Object
  extended by org.apache.lucene.search.Searcher
      extended by 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 nth 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 nth 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.


Copyright © 2000-2010 Apache Software Foundation. All Rights Reserved.