pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/TopTermsRewrite.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/TopTermsRewrite.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;
+import java.util.PriorityQueue;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.Term;
+
+/**
+ * Base rewrite method for collecting only the top terms
+ * via a priority queue.
+ * @lucene.internal Only public to be accessible by spans package.
+ */
+public abstract class TopTermsRewrite<Q extends Query> extends TermCollectingRewrite<Q> {
+
+  private final int size;
+  
+  /** 
+   * Create a TopTermsBooleanQueryRewrite for 
+   * at most <code>size</code> terms.
+   * <p>
+   * NOTE: if {@link BooleanQuery#getMaxClauseCount} is smaller than 
+   * <code>size</code>, then it will be used instead. 
+   */
+  public TopTermsRewrite(int size) {
+    this.size = size;
+  }
+  
+  /** return the maximum priority queue size */
+  public int getSize() {
+    return size;
+  }
+  
+  /** return the maximum size of the priority queue (for boolean rewrites this is BooleanQuery#getMaxClauseCount). */
+  protected abstract int getMaxSize();
+  
+  @Override
+  public Q rewrite(final IndexReader reader, final MultiTermQuery query) throws IOException {
+    final int maxSize = Math.min(size, getMaxSize());
+    final PriorityQueue<ScoreTerm> stQueue = new PriorityQueue<ScoreTerm>();
+    collectTerms(reader, query, new TermCollector() {
+      public boolean collect(Term t, float boost) {
+        // ignore uncompetitive hits
+        if (stQueue.size() >= maxSize && boost <= stQueue.peek().boost)
+          return true;
+        // add new entry in PQ
+        st.term = t;
+        st.boost = boost;
+        stQueue.offer(st);
+        // possibly drop entries from queue
+        st = (stQueue.size() > maxSize) ? stQueue.poll() : new ScoreTerm();
+        return true;
+      }
+      
+      // reusable instance
+      private ScoreTerm st = new ScoreTerm();
+    });
+    
+    final Q q = getTopLevelQuery();
+    for (final ScoreTerm st : stQueue) {
+      addClause(q, st.term, query.getBoost() * st.boost); // add to query
+    }
+    query.incTotalNumberOfTerms(stQueue.size());
+    
+    return q;
+  }
+
+  @Override
+  public int hashCode() {
+    return 31 * size;
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj) return true;
+    if (obj == null) return false;
+    if (getClass() != obj.getClass()) return false;
+    final TopTermsRewrite other = (TopTermsRewrite) obj;
+    if (size != other.size) return false;
+    return true;
+  }
+  
+  private static class ScoreTerm implements Comparable<ScoreTerm> {
+    public Term term;
+    public float boost;
+    
+    public int compareTo(ScoreTerm other) {
+      if (this.boost == other.boost)
+        return other.term.compareTo(this.term);
+      else
+        return Float.compare(this.boost, other.boost);
+    }
+  }
+  
+}