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) method. 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)). 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.

Field Summary

Fields

Modifier and Type	Field	Description
protected List<LeafReaderContext>	leafContexts
protected IndexReaderContext	readerContext

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.
int	count(Query query)	Count how many documents match the given query.
Weight	createNormalizedWeight(Query query, boolean needsScores)	Deprecated. Clients should rewrite the query and then call createWeight(Query, boolean, float) with a boost value of 1f
Weight	createWeight(Query query, boolean needsScores, float boost)	Creates a Weight for the given query, potentially adding caching if possible and configured.
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)
Explanation	explain(Query query, int doc)	Returns an Explanation that describes how doc scored against query.
protected Explanation	explain(Weight weight, int doc)	Expert: low-level implementation method Returns an Explanation that describes how doc scored against weight.
static QueryCache	getDefaultQueryCache()	Expert: Get the default QueryCache or null if the cache is disabled.
static QueryCachingPolicy	getDefaultQueryCachingPolicy()	Expert: Get the default QueryCachingPolicy.
static Similarity	getDefaultSimilarity()	Expert: returns a default Similarity instance.
IndexReader	getIndexReader()	Return the IndexReader this searches.
QueryCache	getQueryCache()	Return the query cache of this IndexSearcher.
QueryCachingPolicy	getQueryCachingPolicy()	Return the query cache of this IndexSearcher.
Similarity	getSimilarity(boolean needsScores)	Expert: Get the Similarity to use to compute scores.
IndexSearcher.LeafSlice[]	getSlices()	Returns the leaf slices used for concurrent searching, or null if no ExecutorService was passed to the constructor.
IndexReaderContext	getTopReaderContext()	Returns this searchers the top-level IndexReaderContext.
Query	rewrite(Query original)	Expert: called to re-write queries into primitive queries.
protected void	search(List<LeafReaderContext> leaves, Weight weight, Collector collector)	Lower-level search API.
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.
TopFieldDocs	search(Query query, 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, Collector results)	Lower-level search API.
<C extends Collector,T> T	search(Query query, CollectorManager<C,T> collectorManager)	Lower-level search API.
TopDocs	searchAfter(ScoreDoc after, Query query, int numHits)	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).
TopFieldDocs	searchAfter(ScoreDoc after, Query query, int numHits, 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.
static void	setDefaultQueryCache(QueryCache defaultQueryCache)	Expert: set the default QueryCache instance.
static void	setDefaultQueryCachingPolicy(QueryCachingPolicy defaultQueryCachingPolicy)	Expert: set the default QueryCachingPolicy instance.
void	setQueryCache(QueryCache queryCache)	Set the QueryCache to use when scores are not needed.
void	setQueryCachingPolicy(QueryCachingPolicy queryCachingPolicy)	Set the QueryCachingPolicy to use for query caching.
void	setSimilarity(Similarity similarity)	Expert: Set the Similarity implementation used by this IndexSearcher.
protected IndexSearcher.LeafSlice[]	slices(List<LeafReaderContext> leaves)	Expert: Creates an array of leaf slices each holding a subset of the given leaves.
TermStatistics	termStatistics(Term term, TermContext context)	Returns TermStatistics for a term.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

readerContext

protected final IndexReaderContext readerContext

leafContexts

protected final List<LeafReaderContext> leafContexts

Constructor Detail

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 close/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(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 close/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()

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

IndexSearcher

public IndexSearcher(IndexReaderContext context)

Creates a searcher searching the provided top-level IndexReaderContext.

See Also:

IndexReaderContext, IndexReader.getContext()

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

Method Detail

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(boolean).

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

getDefaultQueryCache

public static QueryCache getDefaultQueryCache()

Expert: Get the default QueryCache or null if the cache is disabled.

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

setDefaultQueryCache

public static void setDefaultQueryCache(QueryCache defaultQueryCache)

Expert: set the default QueryCache instance.

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

getDefaultQueryCachingPolicy

public static QueryCachingPolicy getDefaultQueryCachingPolicy()

Expert: Get the default QueryCachingPolicy.

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

setDefaultQueryCachingPolicy

public static void setDefaultQueryCachingPolicy(QueryCachingPolicy defaultQueryCachingPolicy)

Expert: set the default QueryCachingPolicy instance.

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

setQueryCache

public void setQueryCache(QueryCache queryCache)

Set the QueryCache to use when scores are not needed. A value of null indicates that query matches should never be cached. This method should be called before starting using this IndexSearcher.

NOTE: When using a query cache, queries should not be modified after they have been passed to IndexSearcher.

See Also:

QueryCache

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

getQueryCache

public QueryCache getQueryCache()

Return the query cache of this IndexSearcher. This will be either the default query cache or the query cache that was last set through setQueryCache(QueryCache). A return value of null indicates that caching is disabled.

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

setQueryCachingPolicy

public void setQueryCachingPolicy(QueryCachingPolicy queryCachingPolicy)

Set the QueryCachingPolicy to use for query caching. This method should be called before starting using this IndexSearcher.

See Also:

QueryCachingPolicy

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

getQueryCachingPolicy

public QueryCachingPolicy getQueryCachingPolicy()

Return the query cache of this IndexSearcher. This will be either the default policy or the policy that was last set through setQueryCachingPolicy(QueryCachingPolicy).

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

slices

protected IndexSearcher.LeafSlice[] slices(List<LeafReaderContext> leaves)

Expert: Creates an array of leaf slices each holding a subset of the given leaves. Each IndexSearcher.LeafSlice is executed in a single thread. By default there will be one IndexSearcher.LeafSlice per leaf (LeafReaderContext).

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)

setSimilarity

public void setSimilarity(Similarity similarity)

Expert: Set the Similarity implementation used by this IndexSearcher.

getSimilarity

public Similarity getSimilarity(boolean needsScores)

Expert: Get the Similarity to use to compute scores. When needsScores is false, this method will return a simple Similarity that does not leverage scoring factors such as norms. When needsScores is true, this returns the Similarity that has been set through setSimilarity(Similarity) or the getDefaultSimilarity() default Similarity if none has been set explicitly.

count

public int count(Query query)
          throws IOException

Count how many documents match the given query.

Throws:

IOException

getSlices

public IndexSearcher.LeafSlice[] getSlices()

Returns the leaf slices used for concurrent searching, or null if no ExecutorService was passed to the constructor.

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

searchAfter

public TopDocs searchAfter(ScoreDoc after,
                           Query query,
                           int numHits)
                    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

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 void search(Query query,
                   Collector results)
            throws IOException

Lower-level search API.

LeafCollector.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,
                           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, 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

search

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

Search implementation with arbitrary sorting.

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 TopFieldDocs searchAfter(ScoreDoc after,
                                Query query,
                                int numHits,
                                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

search

public <C extends Collector,T> T search(Query query,
                                              CollectorManager<C,T> collectorManager)
                                       throws IOException

Lower-level search API. Search all leaves using the given CollectorManager. In contrast to search(Query, Collector), this method will use the searcher's ExecutorService in order to parallelize execution of the collection on the configured leafSlices.

Throws:

IOException

See Also:

CollectorManager

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

search

protected void search(List<LeafReaderContext> leaves,
                      Weight weight,
                      Collector collector)
               throws IOException

Lower-level search API.

LeafCollector.collect(int) is called for every document.

NOTE: this method executes the searches on all given leaves exclusively. To search across all the searchers leaves use leafContexts.

Parameters:

leaves - the searchers leaves to execute the searches on

weight - to match documents

collector - to receive hits

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

explain

protected 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 explain(Query, int).

Throws:

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

IOException

createNormalizedWeight

@Deprecated
public Weight createNormalizedWeight(Query query,
                                     boolean needsScores)
                              throws IOException

Deprecated.

Clients should rewrite the query and then call createWeight(Query, boolean, float) with a boost value of 1f

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

Throws:

IOException

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

createWeight

public Weight createWeight(Query query,
                           boolean needsScores,
                           float boost)
                    throws IOException

Creates a Weight for the given query, potentially adding caching if possible and configured.

Throws:

IOException

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

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

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

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

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