Package org.apache.lucene.search

Class IndexSearcher

java.lang.Object

org.apache.lucene.search.IndexSearcher

public class IndexSearcher
extends Object

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 DirectoryReader.openIfChanged(DirectoryReader) 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 (DirectoryReader.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.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	IndexSearcher.LeafSlice	A class holding a subset of the IndexSearchers leaf contexts to be executed within a single thread.

Constructor Summary

Constructors

Constructor	Description
IndexSearcher(IndexReader r)	Creates a searcher searching the provided index.
IndexSearcher(IndexReaderContext context)	Creates a searcher searching the provided top-level IndexReaderContext.
IndexSearcher(IndexReaderContext context, ExecutorService executor)	Creates a searcher searching the provided top-level IndexReaderContext.
IndexSearcher(IndexReader r, ExecutorService executor)	Runs searches for each segment separately, using the provided ExecutorService.

Method Summary

Modifier and Type	Method	Description
CollectionStatistics	collectionStatistics(String field)	Returns CollectionStatistics for a field.
Weight	createNormalizedWeight(Query query)	Creates a normalized weight for a top-level Query.
Document	doc(int docID)	Sugar for .getIndexReader().document(docID)
Document	doc(int docID, Set<String> fieldsToLoad)	Sugar for .getIndexReader().document(docID, fieldsToLoad)
void	doc(int docID, StoredFieldVisitor fieldVisitor)	Sugar for .getIndexReader().document(docID, fieldVisitor)
final Document	document(int docID, Set<String> fieldsToLoad)	Deprecated. Use doc(int, Set) instead.
Explanation	explain(Query query, int doc)	Returns an Explanation that describes how doc scored against query.
static Similarity	getDefaultSimilarity()	Expert: returns a default Similarity instance.
IndexReader	getIndexReader()	Return the IndexReader this searches.
Similarity	getSimilarity()
IndexReaderContext	getTopReaderContext()	Returns this searchers the top-level IndexReaderContext.
Query	rewrite(Query original)	Expert: called to re-write queries into primitive queries.
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(Query query, 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.
TopFieldDocs	search(Query query, Filter filter, int n, Sort sort, boolean doDocScores, boolean doMaxScore)	Search implementation with arbitrary sorting, plus control over whether hit scores and max score should be computed.
void	search(Query query, Filter filter, Collector results)	Lower-level search API.
TopDocs	searchAfter(ScoreDoc after, Query query, int n)	Finds the top n hits for query where all results are after a previous result (after).
TopDocs	searchAfter(ScoreDoc after, Query query, int n, Sort sort)	Finds the top n hits for query where all results are after a previous result (after).
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, Filter filter, int n, Sort sort)	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, Filter filter, int n, Sort sort, boolean doDocScores, boolean doMaxScore)	Finds the top n hits for query where all results are after a previous result (after), allowing control over whether hit scores and max score should be computed.
void	setSimilarity(Similarity similarity)	Expert: Set the Similarity implementation used by this IndexSearcher.
TermStatistics	termStatistics(Term term, TermContext context)	Returns TermStatistics for a term.
String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

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).

IndexSearcher

public IndexSearcher(IndexReaderContext context,
 ExecutorService executor)

Creates a searcher searching the provided top-level IndexReaderContext.

Given a non-null ExecutorService this method 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).

See Also:

• IndexReaderContext
• IndexReader.getContext()

IndexSearcher

public IndexSearcher(IndexReaderContext context)

Creates a searcher searching the provided top-level IndexReaderContext.

See Also:

• IndexReaderContext
• IndexReader.getContext()

Method Details

getDefaultSimilarity

public static Similarity getDefaultSimilarity()

Expert: returns a default Similarity instance. In general, this method is only called to initialize searchers and writers. User code and query implementations should respect getSimilarity().

getIndexReader

public IndexReader getIndexReader()

Return the IndexReader this searches.

doc

public Document doc(int docID)
             throws IOException

Sugar for .getIndexReader().document(docID)

Throws:

IOException

See Also:

• IndexReader.document(int)

doc

public void doc(int docID,
 StoredFieldVisitor fieldVisitor)
         throws IOException

Sugar for .getIndexReader().document(docID, fieldVisitor)

Throws:

IOException

See Also:

• IndexReader.document(int, StoredFieldVisitor)

doc

public Document doc(int docID,
 Set<String> fieldsToLoad)
             throws IOException

Sugar for .getIndexReader().document(docID, fieldsToLoad)

Throws:

IOException

See Also:

• IndexReader.document(int, Set)

document

@Deprecated
public final Document document(int docID,
 Set<String> fieldsToLoad)
                        throws IOException

Deprecated.

Use doc(int, Set) instead.

Throws:

IOException

setSimilarity

public void setSimilarity(Similarity similarity)

Expert: Set the Similarity implementation used by this IndexSearcher.

getSimilarity

public Similarity getSimilarity()

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 - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

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 - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

IOException

search

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

Finds the top n hits for query.

Throws:

BooleanQuery.TooManyClauses - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

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 - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

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.

Parameters:

query - to match documents

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

results - to receive hits

Throws:

BooleanQuery.TooManyClauses - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

IOException

search

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

Lower-level search API.

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

Throws:

BooleanQuery.TooManyClauses - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

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 search(Query,Filter,int,Sort,boolean,boolean) to control scoring.

Throws:

BooleanQuery.TooManyClauses - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

IOException

search

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

Search implementation with arbitrary sorting, plus control over whether hit scores and max score should be computed. Finds the top n hits for query, applying filter if non-null, and sorting the hits by the criteria in sort. If doDocScores is true then the score of each hit will be computed and returned. If doMaxScore is true then the maximum score over all collected hits will be computed.

Throws:

BooleanQuery.TooManyClauses - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

IOException

searchAfter

public TopDocs searchAfter(ScoreDoc after,
 Query query,
 Filter filter,
 int n,
 Sort sort)
                    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 - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

IOException

search

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

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 - if there is a low-level I/O error

searchAfter

public TopDocs searchAfter(ScoreDoc after,
 Query query,
 int n,
 Sort sort)
                    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 - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

IOException

searchAfter

public TopDocs searchAfter(ScoreDoc after,
 Query query,
 Filter filter,
 int n,
 Sort sort,
 boolean doDocScores,
 boolean doMaxScore)
                    throws IOException

Finds the top n hits for query where all results are after a previous result (after), allowing control over whether hit scores and max score should be computed.

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. If doDocScores is true then the score of each hit will be computed and returned. If doMaxScore is true then the maximum score over all collected hits will be computed.

Throws:

BooleanQuery.TooManyClauses - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

IOException

rewrite

public Query rewrite(Query original)
              throws IOException

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

Throws:

BooleanQuery.TooManyClauses - If a query would exceed BooleanQuery.getMaxClauseCount() clauses.

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

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.IndexSearcher) called, afterwards the Weight is normalized. The returned Weight can then directly be used to get a Scorer.

Throws:

IOException

getTopReaderContext

public IndexReaderContext getTopReaderContext()

Returns this searchers the top-level IndexReaderContext.

See Also:

• IndexReader.getContext()

toString

public String toString()

Overrides:

toString in class Object

termStatistics

public TermStatistics termStatistics(Term term,
 TermContext context)
                              throws IOException

Returns TermStatistics for a term. This can be overridden for example, to return a term's statistics across a distributed collection.

Throws:

IOException

collectionStatistics

public CollectionStatistics collectionStatistics(String field)
                                          throws IOException

Returns CollectionStatistics for a field. This can be overridden for example, to return a field's statistics across a distributed collection.

Throws:

IOException