org.apache.lucene.search
Class Searcher

java.lang.Object
  extended by org.apache.lucene.search.Searcher
All Implemented Interfaces:
Closeable, Searchable
Direct Known Subclasses:
IndexSearcher, MultiSearcher

public abstract class Searcher
extends Object
implements Searchable

An abstract base class for search implementations. Implements the main search methods.

Note that you can only access hits from a Searcher as long as it is not yet closed, otherwise an IOException will be thrown.


Constructor Summary
Searcher()
           
 
Method Summary
abstract  void close()
          Frees resources associated with this Searcher.
protected  Weight createWeight(Query query)
          creates a weight for query
abstract  Document doc(int i)
          Returns the stored fields of document i.
abstract  Document doc(int docid, FieldSelector fieldSelector)
          Get the Document at the nth position.
abstract  int docFreq(Term term)
          Expert: Returns the number of documents containing term.
 int[] docFreqs(Term[] terms)
          Expert: For each term in the terms array, calculates the number of documents containing term.
 Explanation explain(Query query, int doc)
          Returns an Explanation that describes how doc scored against query.
abstract  Explanation explain(Weight weight, int doc)
          Expert: low-level implementation method Returns an Explanation that describes how doc scored against weight.
 Similarity getSimilarity()
          Expert: Return the Similarity implementation used by this Searcher.
abstract  int maxDoc()
          Expert: Returns one greater than the largest possible document number.
abstract  Query rewrite(Query query)
          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.
abstract  void search(Weight weight, Filter filter, Collector results)
          Lower-level search API.
abstract  TopDocs search(Weight weight, Filter filter, int n)
          Expert: Low-level search implementation.
abstract  TopFieldDocs search(Weight weight, Filter filter, int n, Sort sort)
          Expert: Low-level search implementation with arbitrary sorting.
 void setSimilarity(Similarity similarity)
          Expert: Set the Similarity implementation used by this Searcher.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Searcher

public Searcher()
Method Detail

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 IndexSearcher.setDefaultFieldSortScoring(boolean, boolean) to enable scoring.

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 (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.

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 (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
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.

Throws:
BooleanQuery.TooManyClauses
IOException

search

public TopDocs search(Query query,
                      int n)
               throws IOException
Finds the top n hits for query.

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.

Throws:
IOException

setSimilarity

public void setSimilarity(Similarity similarity)
Expert: Set the Similarity implementation used by this Searcher.

See Also:
Similarity.setDefault(Similarity)

getSimilarity

public Similarity getSimilarity()
Expert: Return the Similarity implementation used by this Searcher.

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


createWeight

protected Weight createWeight(Query query)
                       throws IOException
creates a weight for query

Returns:
new weight
Throws:
IOException

docFreqs

public int[] docFreqs(Term[] terms)
               throws IOException
Description copied from interface: Searchable
Expert: For each term in the terms array, calculates the number of documents containing term. Returns an array with these document frequencies. Used to minimize number of remote calls.

Specified by:
docFreqs in interface Searchable
Throws:
IOException

search

public abstract void search(Weight weight,
                            Filter filter,
                            Collector results)
                     throws IOException
Description copied from interface: Searchable
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 (search(Query,int)) is usually more efficient, as it skips non-high-scoring hits.

Specified by:
search in interface Searchable
Parameters:
weight - to match documents
filter - if non-null, used to permit documents to be collected.
results - to receive hits
Throws:
IOException

close

public abstract void close()
                    throws IOException
Description copied from interface: Searchable
Frees resources associated with this Searcher. Be careful not to call this method while you are still using objects that reference this Searchable.

Specified by:
close in interface Closeable
Specified by:
close in interface Searchable
Throws:
IOException

docFreq

public abstract int docFreq(Term term)
                     throws IOException
Description copied from interface: Searchable
Expert: Returns the number of documents containing term.

Specified by:
docFreq in interface Searchable
Throws:
IOException
See Also:
IndexReader.docFreq(Term)

maxDoc

public abstract int maxDoc()
                    throws IOException
Description copied from interface: Searchable
Expert: Returns one greater than the largest possible document number.

Specified by:
maxDoc in interface Searchable
Throws:
IOException
See Also:
IndexReader.maxDoc()

search

public abstract TopDocs search(Weight weight,
                               Filter filter,
                               int n)
                        throws IOException
Description copied from interface: Searchable
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.

Specified by:
search in interface Searchable
Throws:
IOException

doc

public abstract Document doc(int i)
                      throws CorruptIndexException,
                             IOException
Description copied from interface: Searchable
Returns the stored fields of document i.

Specified by:
doc in interface Searchable
Throws:
CorruptIndexException - if the index is corrupt
IOException - if there is a low-level IO error
See Also:
IndexReader.document(int)

doc

public abstract Document doc(int docid,
                             FieldSelector fieldSelector)
                      throws CorruptIndexException,
                             IOException
Description copied from interface: Searchable
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.

Specified by:
doc in interface Searchable
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
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

rewrite

public abstract Query rewrite(Query query)
                       throws IOException
Description copied from interface: Searchable
Expert: called to re-write queries into primitive queries.

Specified by:
rewrite in interface Searchable
Throws:
IOException

explain

public abstract Explanation explain(Weight weight,
                                    int doc)
                             throws IOException
Description copied from interface: Searchable
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).

Specified by:
explain in interface Searchable
Throws:
IOException

search

public abstract TopFieldDocs search(Weight weight,
                                    Filter filter,
                                    int n,
                                    Sort sort)
                             throws IOException
Description copied from interface: Searchable
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.

Specified by:
search in interface Searchable
Throws:
IOException


Copyright © 2000-2010 Apache Software Foundation. All Rights Reserved.