pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / search / ScoreCachingWrappingScorer.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/ScoreCachingWrappingScorer.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/ScoreCachingWrappingScorer.java
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+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 java.io.IOException;
+
+/**
+ * A {@link Scorer} which wraps another scorer and caches the score of the
+ * current document. Successive calls to {@link #score()} will return the same
+ * result and will not invoke the wrapped Scorer's score() method, unless the
+ * current document has changed.<br>
+ * This class might be useful due to the changes done to the {@link Collector}
+ * interface, in which the score is not computed for a document by default, only
+ * if the collector requests it. Some collectors may need to use the score in
+ * several places, however all they have in hand is a {@link Scorer} object, and
+ * might end up computing the score of a document more than once.
+ */
+public class ScoreCachingWrappingScorer extends Scorer {
+
+  private final Scorer scorer;
+  private int curDoc = -1;
+  private float curScore;
+  
+  /** Creates a new instance by wrapping the given scorer. */
+  public ScoreCachingWrappingScorer(Scorer scorer) {
+    super(scorer.getSimilarity(), scorer.weight);
+    this.scorer = scorer;
+  }
+
+  @Override
+  protected boolean score(Collector collector, int max, int firstDocID) throws IOException {
+    return scorer.score(collector, max, firstDocID);
+  }
+
+  @Override
+  public Similarity getSimilarity() {
+    return scorer.getSimilarity();
+  }
+  
+  @Override
+  public float score() throws IOException {
+    int doc = scorer.docID();
+    if (doc != curDoc) {
+      curScore = scorer.score();
+      curDoc = doc;
+    }
+    
+    return curScore;
+  }
+
+  @Override
+  public int docID() {
+    return scorer.docID();
+  }
+
+  @Override
+  public int nextDoc() throws IOException {
+    return scorer.nextDoc();
+  }
+  
+  @Override
+  public void score(Collector collector) throws IOException {
+    scorer.score(collector);
+  }
+  
+  @Override
+  public int advance(int target) throws IOException {
+    return scorer.advance(target);
+  }
+  
+}