org.apache.lucene.search

Class Searcher

Implemented Interfaces:
Remote, Searchable
Known Direct 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.

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)
Expert: Returns the stored fields of document i.
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.
Hits
search(Query query)
Returns the documents matching query.
Hits
search(Query query, Filter filter)
Returns the documents matching query and filter.
TopDocs
search(Query query, Filter filter, int n)
Expert: Low-level search implementation.
TopFieldDocs
search(Query query, Filter filter, int n, Sort sort)
Expert: Low-level search implementation with arbitrary sorting.
void
search(Query query, Filter filter, HitCollector results)
Lower-level search API.
Hits
search(Query query, Filter filter, Sort sort)
Returns documents matching query and filter, sorted by sort.
void
search(Query query, HitCollector results)
Lower-level search API.
Hits
search(Query query, Sort sort)
Returns documents matching query sorted by sort.
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.
abstract void
search(Weight weight, Filter filter, HitCollector results)
Lower-level search API.
void
setSimilarity(Similarity similarity)
Expert: Set the Similarity implementation used by this Searcher.

Method Details

close

public abstract void close()
            throws IOException
Specified by:
close in interface Searchable

createWeight

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

doc

public abstract Document doc(int i)
            throws IOException
Expert: Returns the stored fields of document i. Called by HitCollector implementations.
Specified by:
doc in interface Searchable

docFreq

public abstract int docFreq(Term term)
            throws IOException
Expert: Returns the number of documents containing term. Called by search code to compute term weights.
Specified by:
docFreq in interface Searchable

docFreqs

public int[] docFreqs(Term[] terms)
            throws IOException
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

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.

Specified by:
explain in interface Searchable

explain

public abstract 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).

Specified by:
explain in interface Searchable

getSimilarity

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

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


maxDoc

public abstract int maxDoc()
            throws IOException
Expert: Returns one greater than the largest possible document number. Called by search code to compute term weights.
Specified by:
maxDoc in interface Searchable

rewrite

public abstract Query rewrite(Query query)
            throws IOException
Expert: called to re-write queries into primitive queries.
Specified by:
rewrite in interface Searchable

search

public final Hits search(Query query)
            throws IOException
Returns the documents matching query.

search

public Hits search(Query query,
                   Filter filter)
            throws IOException
Returns the documents matching query and filter.

search

public TopDocs search(Query query,
                      Filter filter,
                      int n)
            throws IOException
Expert: Low-level search implementation. Finds the top n hits for query, applying filter if non-null.

Called by Hits.

Applications should usually call search(Query) or search(Query,Filter) instead.

Specified by:
search in interface Searchable

search

public TopFieldDocs search(Query query,
                           Filter filter,
                           int n,
                           Sort sort)
            throws IOException
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,Sort) instead.

Specified by:
search in interface Searchable

search

public void search(Query query,
                   Filter filter,
                   HitCollector results)
            throws IOException
Lower-level search API.

HitCollector.collect(int,float) is called for every non-zero scoring document.
HitCollector-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)) is usually more efficient, as it skips non-high-scoring hits.

Specified by:
search in interface Searchable
Parameters:
query - to match documents
filter - if non-null, a bitset used to eliminate some documents
results - to receive hits

search

public Hits search(Query query,
                   Filter filter,
                   Sort sort)
            throws IOException
Returns documents matching query and filter, sorted by sort.

search

public void search(Query query,
                   HitCollector results)
            throws IOException
Lower-level search API.

HitCollector.collect(int,float) is called for every non-zero scoring document.

Applications should only use this if they need all of the matching documents. The high-level search API (search(Query)) 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.


search

public Hits search(Query query,
                   Sort sort)
            throws IOException
Returns documents matching query sorted by sort.

search

public abstract TopDocs search(Weight weight,
                               Filter filter,
                               int n)
            throws IOException
Expert: Low-level search implementation. Finds the top n hits for query, applying filter if non-null.

Called by Hits.

Applications should usually call search(Query) or search(Query,Filter) instead.

Specified by:
search in interface Searchable

search

public abstract TopFieldDocs search(Weight weight,
                                    Filter filter,
                                    int n,
                                    Sort sort)
            throws IOException
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,Sort) instead.

Specified by:
search in interface Searchable

search

public abstract void search(Weight weight,
                            Filter filter,
                            HitCollector results)
            throws IOException
Lower-level search API.

HitCollector.collect(int,float) is called for every non-zero scoring document.
HitCollector-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)) 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, a bitset used to eliminate some documents
results - to receive hits

setSimilarity

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

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