org.apache.lucene.search
Class IndexSearcher

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

All Implemented Interfaces:

Closeable, Searchable

Direct Known Subclasses:

AssertingIndexSearcher, CheckHits.ExplanationAssertingSearcher

public class IndexSearcher
extends Searcher

Implements search over a single IndexReader.

Applications usually need only call the inherited search(Query,int) or search(Query,Filter,int) methods. For performance reasons, if your index is unchanging, you should share a single IndexSearcher instance across multiple searches instead of creating a new one per-search. If your index has changed and you wish to see the changes reflected in searching, you should use IndexReader.openIfChanged(org.apache.lucene.index.IndexReader) to obtain a new reader and then create a new IndexSearcher from that. Also, for low-latency turnaround it's best to use a near-real-time reader (IndexReader.open(IndexWriter,boolean)). Once you have a new IndexReader, it's relatively cheap to create a new IndexSearcher from it.

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.

Field Summary

protected int[]	docStarts
protected IndexReader[]	subReaders
protected IndexSearcher[]	subSearchers

Constructor Summary

IndexSearcher(Directory path)
Deprecated. use IndexSearcher(IndexReader) instead.

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

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

IndexSearcher(IndexReader r, ExecutorService executor)
Runs searches for each segment separately, using the provided ExecutorService.

IndexSearcher(IndexReader reader, IndexReader[] subReaders, int[] docStarts)
Expert: directly specify the reader, subReaders and their docID starts.

IndexSearcher(IndexReader reader, IndexReader[] subReaders, int[] docStarts, ExecutorService executor)
Expert: directly specify the reader, subReaders and their docID starts, and an ExecutorService.

Method Summary

void	close() Note that the underlying IndexReader is not closed, if IndexSearcher was constructed with IndexSearcher(IndexReader r).
Weight	createNormalizedWeight(Query query) Creates a normalized weight for a top-level Query.
Document	doc(int docID) Returns the stored fields of document i.
Document	doc(int docID, FieldSelector fieldSelector) Get the Document at the nth position.
int	docFreq(Term term) Returns total docFreq for this term.
Explanation	explain(Query query, int doc) Returns an Explanation that describes how doc scored against query.
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<IndexReader> allSubReaders, IndexReader r)
IndexReader	getIndexReader() Return the IndexReader this searches.
Similarity	getSimilarity() Expert: Return the Similarity implementation used by this Searcher.
IndexReader[]	getSubReaders() Returns the atomic subReaders used by this searcher.
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(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.
TopFieldDocs	search(Query query, int n, Sort sort) Search implementation with arbitrary sorting and no filter.
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.
protected 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.
protected TopDocs	search(Weight weight, Filter filter, ScoreDoc after, int nDocs) Expert: Low-level search implementation.
TopDocs	searchAfter(ScoreDoc after, Query query, Filter filter, int n) Finds the top n hits for query, applying filter if non-null, where all results are after a previous result (after).
TopDocs	searchAfter(ScoreDoc after, Query query, int n) Finds the top n hits for query where all results are after a previous result (after).
void	setDefaultFieldSortScoring(boolean doTrackScores, boolean doMaxScore) By default, no scores are computed when sorting by field (using search(Query,Filter,int,Sort)).
void	setSimilarity(Similarity similarity) Expert: Set the Similarity implementation used by this Searcher.
String	toString()

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

createWeight, docFreqs

Methods inherited from class java.lang.Object

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

Field Detail

subReaders

protected final IndexReader[] subReaders

docStarts

protected final int[] docStarts

subSearchers

protected final IndexSearcher[] subSearchers

Constructor Detail

IndexSearcher

@Deprecated
public IndexSearcher(Directory path)
              throws CorruptIndexException,
                     IOException

Deprecated. use IndexSearcher(IndexReader) instead.

Creates a searcher searching the index in the named directory, with readOnly=true

Parameters:

path - directory where IndexReader will be opened

Throws:

CorruptIndexException - if the index is corrupt

IOException - if there is a low-level IO error

IndexSearcher

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

Deprecated. Use IndexSearcher(IndexReader) 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(IndexReader r)

Creates a searcher searching the provided index.

IndexSearcher

public IndexSearcher(IndexReader r,
                     ExecutorService executor)

Runs searches for each segment separately, using the provided ExecutorService. IndexSearcher will not shutdown/awaitTermination this ExecutorService on close; you must do so, eventually, on your own. NOTE: if you are using NIOFSDirectory, do not use the shutdownNow method of ExecutorService as this uses Thread.interrupt under-the-hood which can silently close file descriptors (see LUCENE-2239).

WARNING: This API is experimental and might change in incompatible ways in the next release.

IndexSearcher

public IndexSearcher(IndexReader reader,
                     IndexReader[] subReaders,
                     int[] docStarts)

Expert: directly specify the reader, subReaders and their docID starts.

WARNING: This API is experimental and might change in incompatible ways in the next release.

IndexSearcher

public IndexSearcher(IndexReader reader,
                     IndexReader[] subReaders,
                     int[] docStarts,
                     ExecutorService executor)

Expert: directly specify the reader, subReaders and their docID starts, and an ExecutorService. In this case, each segment will be separately searched using the ExecutorService. IndexSearcher will not shutdown/awaitTermination this ExecutorService on close; you must do so, eventually, on your own. NOTE: if you are using NIOFSDirectory, do not use the shutdownNow method of ExecutorService as this uses Thread.interrupt under-the-hood which can silently close file descriptors (see LUCENE-2239).

WARNING: This API is experimental and might change in incompatible ways in the next release.

Method Detail

gatherSubReaders

protected void gatherSubReaders(List<IndexReader> allSubReaders,
                                IndexReader r)

getIndexReader

public IndexReader getIndexReader()

Return the IndexReader this searches.

getSubReaders

public IndexReader[] getSubReaders()

Returns the atomic subReaders used by this searcher.

maxDoc

public int maxDoc()

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

Specified by:

maxDoc in interface Searchable

Specified by:

maxDoc in class Searcher

See Also:

IndexReader.maxDoc()

docFreq

public int docFreq(Term term)
            throws IOException

Returns total docFreq for this 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 docID)
             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 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

Specified by:

doc in class Searcher

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

setSimilarity

public void setSimilarity(Similarity similarity)

Expert: Set the Similarity implementation used by this Searcher.

Overrides:

setSimilarity in class Searcher

See Also:

Similarity.setDefault(Similarity)

getSimilarity

public Similarity getSimilarity()

Description copied from class: Searcher

Expert: Return the Similarity implementation used by this Searcher.

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

Overrides:

getSimilarity in class Searcher

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 is closed.

Specified by:

close in interface Closeable

Specified by:

close in interface Searchable

Specified by:

close in class Searcher

Throws:

IOException

searchAfter

public TopDocs searchAfter(ScoreDoc after,
                           Query query,
                           int n)
                    throws IOException

Finds the top n hits for query where all results are after a previous result (after).

By passing the bottom result from a previous page as after, this method can be used for efficient 'deep-paging' across potentially large result sets.

Throws:

BooleanQuery.TooManyClauses

IOException

searchAfter

public TopDocs searchAfter(ScoreDoc after,
                           Query query,
                           Filter filter,
                           int n)
                    throws IOException

Finds the top n hits for query, applying filter if non-null, where all results are after a previous result (after).

By passing the bottom result from a previous page as after, this method can be used for efficient 'deep-paging' across potentially large result sets.

Throws:

BooleanQuery.TooManyClauses

IOException

search

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

Finds the top n hits for query.

Overrides:

search in class Searcher

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.

Overrides:

search in class Searcher

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 (Searcher.search(Query, Filter, int)) is usually more efficient, as it skips non-high-scoring hits.

Overrides:

search in class Searcher

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 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 (Searcher.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.

Overrides:

search in class Searcher

Throws:

BooleanQuery.TooManyClauses

IOException

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 setDefaultFieldSortScoring(boolean, boolean) to enable scoring.

Overrides:

search in class Searcher

Throws:

BooleanQuery.TooManyClauses

IOException

search

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

Search implementation with arbitrary sorting and no filter.

Overrides:

search in class Searcher

Parameters:

query - The query to search for

n - Return only the top n results

sort - The Sort object

Returns:

The top docs, sorted according to the supplied Sort instance

Throws:

IOException

search

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

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

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

Specified by:

search in interface Searchable

Specified by:

search in class Searcher

Throws:

BooleanQuery.TooManyClauses

IOException

search

protected TopDocs search(Weight weight,
                         Filter filter,
                         ScoreDoc after,
                         int nDocs)
                  throws IOException

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

Throws:

BooleanQuery.TooManyClauses

IOException

search

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

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:

BooleanQuery.TooManyClauses

IOException

search

protected 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

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,int)) 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:

BooleanQuery.TooManyClauses

IOException

rewrite

public Query rewrite(Query original)
              throws IOException

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

Specified by:

rewrite in interface Searchable

Specified by:

rewrite in class Searcher

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.

Overrides:

explain in class Searcher

Throws:

IOException

explain

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

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:

BooleanQuery.TooManyClauses

IOException

setDefaultFieldSortScoring

public void setDefaultFieldSortScoring(boolean doTrackScores,
                                       boolean doMaxScore)

By default, no scores are computed when sorting by field (using 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.

createNormalizedWeight

public Weight createNormalizedWeight(Query query)
                              throws IOException

Creates a normalized weight for a top-level Query. The query is rewritten by this method and Query.createWeight(org.apache.lucene.search.Searcher) called, afterwards the Weight is normalized. The returned Weight can then directly be used to get a Scorer.

Overrides:

createNormalizedWeight in class Searcher

Throws:

IOException

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

toString

public String toString()

Overrides:

toString in class Object