org.apache.lucene.search
Class MultiSearcher

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

public class MultiSearcher
extends Searcher

Implements search over a set of Searchables.

Applications usually need only call the inherited Searcher.search(Query,int) or Searcher.search(Query,Filter,int) methods.


Constructor Summary
MultiSearcher(Searchable... searchables)
          Creates a searcher which searches searchers.
 
Method Summary
 void close()
          Frees resources associated with this Searcher.
protected  Weight createWeight(Query original)
          Create weight in multiple index scenario.
 Document doc(int n)
          Returns the stored fields of document i.
 Document doc(int n, FieldSelector fieldSelector)
          Get the Document at the nth position.
 int docFreq(Term term)
          Expert: Returns the number of documents containing term.
 Explanation explain(Weight weight, int doc)
          Expert: low-level implementation method Returns an Explanation that describes how doc scored against weight.
 Searchable[] getSearchables()
          Return the array of Searchables this searches.
protected  int[] getStarts()
           
 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(Weight weight, Filter filter, Collector collector)
          Lower-level search API.
 TopDocs search(Weight weight, Filter filter, int nDocs)
          Expert: Low-level search implementation.
 TopFieldDocs search(Weight weight, Filter filter, int n, Sort sort)
          Expert: Low-level search implementation with arbitrary sorting.
 int subDoc(int n)
          Returns the document number of document n within its sub-index.
 int subSearcher(int n)
          Returns index of the searcher for document n in the array used to construct this searcher.
 
Methods inherited from class org.apache.lucene.search.Searcher
docFreqs, explain, getSimilarity, search, search, search, search, search, setSimilarity
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

MultiSearcher

public MultiSearcher(Searchable... searchables)
              throws IOException
Creates a searcher which searches searchers.

Throws:
IOException
Method Detail

getSearchables

public Searchable[] getSearchables()
Return the array of Searchables this searches.


getStarts

protected int[] getStarts()

close

public 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
Specified by:
close in class Searcher
Throws:
IOException

docFreq

public 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
Specified by:
docFreq in class Searcher
Throws:
IOException
See Also:
IndexReader.docFreq(Term)

doc

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

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

doc

public Document doc(int n,
                    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
Specified by:
doc in class Searcher
Parameters:
n - 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

subSearcher

public int subSearcher(int n)
Returns index of the searcher for document n in the array used to construct this searcher.


subDoc

public int subDoc(int n)
Returns the document number of document n within its sub-index.


maxDoc

public 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
Specified by:
maxDoc in class Searcher
Throws:
IOException
See Also:
IndexReader.maxDoc()

search

public TopDocs search(Weight weight,
                      Filter filter,
                      int nDocs)
               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 Searcher.search(Query,int) or Searcher.search(Query,Filter,int) instead.

Specified by:
search in interface Searchable
Specified by:
search in class Searcher
Throws:
IOException

search

public 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 Searcher.search(Query,Filter,int,Sort) instead.

Specified by:
search in interface Searchable
Specified by:
search in class Searcher
Throws:
IOException

search

public void search(Weight weight,
                   Filter filter,
                   Collector collector)
            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 (Searcher.search(Query,int)) is usually more efficient, as it skips non-high-scoring hits.

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

rewrite

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

Specified by:
rewrite in interface Searchable
Specified by:
rewrite in class Searcher
Throws:
IOException

explain

public 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 Searcher.explain(Query, int).

Specified by:
explain in interface Searchable
Specified by:
explain in class Searcher
Throws:
IOException

createWeight

protected Weight createWeight(Query original)
                       throws IOException
Create weight in multiple index scenario. Distributed query processing is done in the following steps: 1. rewrite query 2. extract necessary terms 3. collect dfs for these terms from the Searchables 4. create query weight using aggregate dfs. 5. distribute that weight to Searchables 6. merge results Steps 1-4 are done here, 5+6 in the search() methods

Overrides:
createWeight in class Searcher
Returns:
rewritten queries
Throws:
IOException


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