package org.apache.lucene.search;
/**
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.IndexReader; // for javadoc
/** The interface for search implementations.
*
* <p>Implementations provide search over a single index, over multiple
* indices, and over indices on remote servers.
*/
public interface Searchable extends java.rmi.Remote {
/** Lower-level search API.
*
* <p>{@link HitCollector#collect(int,float)} is called for every non-zero
* scoring document.
*
* <p>Applications should only use this if they need <i>all</i> of the
* matching documents. The high-level search API ({@link
* Searcher#search(Query)}) is usually more efficient, as it skips
* non-high-scoring hits.
*
* @param query to match documents
* @param filter if non-null, a bitset used to eliminate some documents
* @param results to receive hits
*/
void search(Query query, Filter filter, HitCollector results)
throws IOException;
/** Frees resources associated with this Searcher.
* Be careful not to call this method while you are still using objects
* like {@link Hits}.
*/
void close() throws IOException;
/** Expert: Returns the number of documents containing <code>term</code>.
* Called by search code to compute term weights.
* @see IndexReader#docFreq(Term).
*/
int docFreq(Term term) throws IOException;
/** Expert: Returns one greater than the largest possible document number.
* Called by search code to compute term weights.
* @see IndexReader#maxDoc().
*/
int maxDoc() throws IOException;
/** Expert: Low-level search implementation. Finds the top <code>n</code>
* hits for <code>query</code>, applying <code>filter</code> if non-null.
*
* <p>Called by {@link Hits}.
*
* <p>Applications should usually call {@link Searcher#search(Query)} or
* {@link Searcher#search(Query,Filter)} instead.
*/
TopDocs search(Query query, Filter filter, int n) throws IOException;
/** Expert: Returns the stored fields of document <code>i</code>.
* Called by {@link HitCollector} implementations.
* @see IndexReader#document(int).
*/
Document doc(int i) throws IOException;
/** Expert: called to re-write queries into primitive queries. */
Query rewrite(Query query) throws IOException;
/** Returns an Explanation that describes how <code>doc</code> scored against
* <code>query</code>.
*
* <p>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.
*/
Explanation explain(Query query, int doc) throws IOException;
/** Expert: Low-level search implementation with arbitrary sorting. Finds
* the top <code>n</code> hits for <code>query</code>, applying
* <code>filter</code> if non-null, and sorting the hits by the criteria in
* <code>sort</code>.
*
* <p>Applications should usually call {@link
* Searcher#search(Query,Filter,Sort)} instead.
*/
TopFieldDocs search(Query query, Filter filter, int n, Sort sort)
throws IOException;
}
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