+++ /dev/null
-package org.apache.lucene.search;
-
-/**
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You 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 org.apache.lucene.util.PriorityQueue;
-
-/**
- * A base class for all collectors that return a {@link TopDocs} output. This
- * collector allows easy extension by providing a single constructor which
- * accepts a {@link PriorityQueue} as well as protected members for that
- * priority queue and a counter of the number of total hits.<br>
- * Extending classes can override any of the methods to provide their own
- * implementation, as well as avoid the use of the priority queue entirely by
- * passing null to {@link #TopDocsCollector(PriorityQueue)}. In that case
- * however, you might want to consider overriding all methods, in order to avoid
- * a NullPointerException.
- */
-public abstract class TopDocsCollector<T extends ScoreDoc> extends Collector {
-
- // This is used in case topDocs() is called with illegal parameters, or there
- // simply aren't (enough) results.
- protected static final TopDocs EMPTY_TOPDOCS = new TopDocs(0, new ScoreDoc[0], Float.NaN);
-
- /**
- * The priority queue which holds the top documents. Note that different
- * implementations of PriorityQueue give different meaning to 'top documents'.
- * HitQueue for example aggregates the top scoring documents, while other PQ
- * implementations may hold documents sorted by other criteria.
- */
- protected PriorityQueue<T> pq;
-
- /** The total number of documents that the collector encountered. */
- protected int totalHits;
-
- protected TopDocsCollector(PriorityQueue<T> pq) {
- this.pq = pq;
- }
-
- /**
- * Populates the results array with the ScoreDoc instances. This can be
- * overridden in case a different ScoreDoc type should be returned.
- */
- protected void populateResults(ScoreDoc[] results, int howMany) {
- for (int i = howMany - 1; i >= 0; i--) {
- results[i] = pq.pop();
- }
- }
-
- /**
- * Returns a {@link TopDocs} instance containing the given results. If
- * <code>results</code> is null it means there are no results to return,
- * either because there were 0 calls to collect() or because the arguments to
- * topDocs were invalid.
- */
- protected TopDocs newTopDocs(ScoreDoc[] results, int start) {
- return results == null ? EMPTY_TOPDOCS : new TopDocs(totalHits, results);
- }
-
- /** The total number of documents that matched this query. */
- public int getTotalHits() {
- return totalHits;
- }
-
- /** Returns the top docs that were collected by this collector. */
- public TopDocs topDocs() {
- // In case pq was populated with sentinel values, there might be less
- // results than pq.size(). Therefore return all results until either
- // pq.size() or totalHits.
- return topDocs(0, totalHits < pq.size() ? totalHits : pq.size());
- }
-
- /**
- * Returns the documents in the rage [start .. pq.size()) that were collected
- * by this collector. Note that if start >= pq.size(), an empty TopDocs is
- * returned.<br>
- * This method is convenient to call if the application always asks for the
- * last results, starting from the last 'page'.<br>
- * <b>NOTE:</b> you cannot call this method more than once for each search
- * execution. If you need to call it more than once, passing each time a
- * different <code>start</code>, you should call {@link #topDocs()} and work
- * with the returned {@link TopDocs} object, which will contain all the
- * results this search execution collected.
- */
- public TopDocs topDocs(int start) {
- // In case pq was populated with sentinel values, there might be less
- // results than pq.size(). Therefore return all results until either
- // pq.size() or totalHits.
- return topDocs(start, totalHits < pq.size() ? totalHits : pq.size());
- }
-
- /**
- * Returns the documents in the rage [start .. start+howMany) that were
- * collected by this collector. Note that if start >= pq.size(), an empty
- * TopDocs is returned, and if pq.size() - start < howMany, then only the
- * available documents in [start .. pq.size()) are returned.<br>
- * This method is useful to call in case pagination of search results is
- * allowed by the search application, as well as it attempts to optimize the
- * memory used by allocating only as much as requested by howMany.<br>
- * <b>NOTE:</b> you cannot call this method more than once for each search
- * execution. If you need to call it more than once, passing each time a
- * different range, you should call {@link #topDocs()} and work with the
- * returned {@link TopDocs} object, which will contain all the results this
- * search execution collected.
- */
- public TopDocs topDocs(int start, int howMany) {
-
- // In case pq was populated with sentinel values, there might be less
- // results than pq.size(). Therefore return all results until either
- // pq.size() or totalHits.
- int size = totalHits < pq.size() ? totalHits : pq.size();
-
- // Don't bother to throw an exception, just return an empty TopDocs in case
- // the parameters are invalid or out of range.
- if (start < 0 || start >= size || howMany <= 0) {
- return newTopDocs(null, start);
- }
-
- // We know that start < pqsize, so just fix howMany.
- howMany = Math.min(size - start, howMany);
- ScoreDoc[] results = new ScoreDoc[howMany];
-
- // pq's pop() returns the 'least' element in the queue, therefore need
- // to discard the first ones, until we reach the requested range.
- // Note that this loop will usually not be executed, since the common usage
- // should be that the caller asks for the last howMany results. However it's
- // needed here for completeness.
- for (int i = pq.size() - start - howMany; i > 0; i--) { pq.pop(); }
-
- // Get the requested results from pq.
- populateResults(results, howMany);
-
- return newTopDocs(results, start);
- }
-
-}
fnp / pylucene.git / blobdiff