public class

IndexSearcher

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

Class Overview

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 reopen() 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 (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.

Summary

Fields
protected final int[] docStarts
protected final IndexReader[] subReaders
protected final IndexSearcher[] subSearchers
Public Constructors
IndexSearcher(Directory path)
Creates a searcher searching the index in the named directory, with readOnly=true
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(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.
Public Methods
void close()
Note that the underlying IndexReader is not closed, if IndexSearcher was constructed with IndexSearcher(IndexReader r).
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.
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, 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.
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.
TopFieldDocs search(Query query, Filter filter, int n, Sort sort)
Search implementation with arbitrary sorting.
void search(Query query, Collector results)
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.
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()
Protected Methods
Weight createWeight(Query query)
creates a weight for query
void gatherSubReaders(List<IndexReader> allSubReaders, IndexReader r)
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.
[Expand]
Inherited Methods
From class org.apache.lucene.search.Searcher
From class java.lang.Object
From interface java.io.Closeable
From interface org.apache.lucene.search.Searchable

Fields

protected final int[] docStarts

protected final IndexReader[] subReaders

protected final IndexSearcher[] subSearchers

Public Constructors

public IndexSearcher (Directory path)

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

public IndexSearcher (Directory path, boolean readOnly)

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

public IndexSearcher (IndexReader r)

Creates a searcher searching the provided index.

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).

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

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

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).

Public Methods

public void close ()

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.

Throws
IOException

public Document doc (int docID)

Returns the stored fields of document i.

public Document doc (int docID, FieldSelector fieldSelector)

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
docID 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

public int docFreq (Term term)

Returns total docFreq for this term.

Throws
IOException

public Explanation explain (Query query, int doc)

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

public Explanation explain (Weight weight, int doc)

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).

public IndexReader getIndexReader ()

Return the IndexReader this searches.

public Similarity getSimilarity ()

Expert: Return the Similarity implementation used by this Searcher.

This defaults to the current value of getDefault().

public IndexReader[] getSubReaders ()

Returns the atomic subReaders used by this searcher.

public int maxDoc ()

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

See Also

public Query rewrite (Query original)

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

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

Lower-level search API.

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

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

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

public TopDocs search (Query query, int n)

Finds the top n hits for query.

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

Search implementation with arbitrary sorting and no filter.

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

public void search (Weight weight, Filter filter, Collector collector)

Lower-level search API.

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.

Parameters
weight to match documents
filter if non-null, used to permit documents to be collected.
collector to receive hits

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

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.

public void search (Query query, Collector results)

Lower-level search API.

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.

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

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.

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

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.

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.

public void setSimilarity (Similarity similarity)

Expert: Set the Similarity implementation used by this Searcher.

public String toString ()

Protected Methods

protected Weight createWeight (Query query)

creates a weight for query

Returns
  • new weight
Throws
IOException

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

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.

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

Throws
IOException