pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/ScoringRewrite.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/ScoringRewrite.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 org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.search.MultiTermQuery.RewriteMethod;
+
+/** @lucene.internal Only public to be accessible by spans package. */
+public abstract class ScoringRewrite<Q extends Query> extends TermCollectingRewrite<Q> {
+
+  /** A rewrite method that first translates each term into
+   *  {@link BooleanClause.Occur#SHOULD} clause in a
+   *  BooleanQuery, and keeps the scores as computed by the
+   *  query.  Note that typically such scores are
+   *  meaningless to the user, and require non-trivial CPU
+   *  to compute, so it's almost always better to use {@link
+   *  MultiTermQuery#CONSTANT_SCORE_AUTO_REWRITE_DEFAULT} instead.
+   *
+   *  <p><b>NOTE</b>: This rewrite method will hit {@link
+   *  BooleanQuery.TooManyClauses} if the number of terms
+   *  exceeds {@link BooleanQuery#getMaxClauseCount}.
+   *
+   *  @see #setRewriteMethod */
+  public final static ScoringRewrite<BooleanQuery> SCORING_BOOLEAN_QUERY_REWRITE = new ScoringRewrite<BooleanQuery>() {
+    @Override
+    protected BooleanQuery getTopLevelQuery() {
+      return new BooleanQuery(true);
+    }
+    
+    @Override
+    protected void addClause(BooleanQuery topLevel, Term term, float boost) {
+      final TermQuery tq = new TermQuery(term);
+      tq.setBoost(boost);
+      topLevel.add(tq, BooleanClause.Occur.SHOULD);
+    }
+    
+    // Make sure we are still a singleton even after deserializing
+    protected Object readResolve() {
+      return SCORING_BOOLEAN_QUERY_REWRITE;
+    }    
+  };
+  
+  /** Like {@link #SCORING_BOOLEAN_QUERY_REWRITE} except
+   *  scores are not computed.  Instead, each matching
+   *  document receives a constant score equal to the
+   *  query's boost.
+   * 
+   *  <p><b>NOTE</b>: This rewrite method will hit {@link
+   *  BooleanQuery.TooManyClauses} if the number of terms
+   *  exceeds {@link BooleanQuery#getMaxClauseCount}.
+   *
+   *  @see #setRewriteMethod */
+  public final static RewriteMethod CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE = new RewriteMethod() {
+    @Override
+    public Query rewrite(IndexReader reader, MultiTermQuery query) throws IOException {
+      final BooleanQuery bq = SCORING_BOOLEAN_QUERY_REWRITE.rewrite(reader, query);
+      // TODO: if empty boolean query return NullQuery?
+      if (bq.clauses().isEmpty())
+        return bq;
+      // strip the scores off
+      final Query result = new ConstantScoreQuery(bq);
+      result.setBoost(query.getBoost());
+      return result;
+    }
+
+    // Make sure we are still a singleton even after deserializing
+    protected Object readResolve() {
+      return CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE;
+    }
+  };
+
+  @Override
+  public Q rewrite(final IndexReader reader, final MultiTermQuery query) throws IOException {
+    final Q result = getTopLevelQuery();
+    final int[] size = new int[1]; // "trick" to be able to make it final
+    collectTerms(reader, query, new TermCollector() {
+      public boolean collect(Term t, float boost) throws IOException {
+        addClause(result, t, query.getBoost() * boost);
+        size[0]++;
+        return true;
+      }
+    });
+    query.incTotalNumberOfTerms(size[0]);
+    return result;
+  }
+}