IndexSearcher (Lucene 6.6.3 API)

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 and Description
`static class`	`IndexSearcher.LeafSlice` A class holding a subset of the `IndexSearcher`s leaf contexts to be executed within a single thread.

Field Summary

Fields
Modifier and Type	Field and Description
`protected List<LeafReaderContext>`	`leafContexts`
`protected IndexSearcher.LeafSlice[]`	`leafSlices` used with executor - each slice holds a set of leafs executed within one thread
`protected IndexReaderContext`	`readerContext`

Constructor Summary

Constructors
Constructor and 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

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and 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)` Creates a normalized weight for a top-level `Query`.
`Weight`	`createWeight(Query query, boolean needsScores)` 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.
`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.
`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`	`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.
`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
```
  - leafSlices
```
protected final IndexSearcher.LeafSlice[] leafSlices
```
    used with executor - each slice holds a set of leafs executed within one thread
- 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
  - 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
```
public Weight createNormalizedWeight(Query query,
                                     boolean needsScores)
                              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, boolean) 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)
                    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.

Class IndexSearcher

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

readerContext

leafContexts

leafSlices

Constructor Detail

IndexSearcher

IndexSearcher

IndexSearcher

IndexSearcher

Method Detail

getDefaultSimilarity

getDefaultQueryCache

setDefaultQueryCache

getDefaultQueryCachingPolicy

setDefaultQueryCachingPolicy

setQueryCache

getQueryCache

setQueryCachingPolicy

getQueryCachingPolicy

slices

getIndexReader

doc

doc

doc

setSimilarity

getSimilarity

count

searchAfter

search

search

search

search

searchAfter

searchAfter

search

search

rewrite

explain

explain

createNormalizedWeight

createWeight

getTopReaderContext

toString

termStatistics

collectionStatistics