--- /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 java.io.IOException;
+import java.io.Serializable;
+
+import org.apache.lucene.index.IndexReader;
+
+/**
+ * Expert: Calculate query weights and build query scorers.
+ * <p>
+ * The purpose of {@link Weight} is to ensure searching does not
+ * modify a {@link Query}, so that a {@link Query} instance can be reused. <br>
+ * {@link Searcher} dependent state of the query should reside in the
+ * {@link Weight}. <br>
+ * {@link IndexReader} dependent state should reside in the {@link Scorer}.
+ * <p>
+ * A <code>Weight</code> is used in the following way:
+ * <ol>
+ * <li>A <code>Weight</code> is constructed by a top-level query, given a
+ * <code>Searcher</code> ({@link Query#createWeight(Searcher)}).
+ * <li>The {@link #sumOfSquaredWeights()} method is called on the
+ * <code>Weight</code> to compute the query normalization factor
+ * {@link Similarity#queryNorm(float)} of the query clauses contained in the
+ * query.
+ * <li>The query normalization factor is passed to {@link #normalize(float)}. At
+ * this point the weighting is complete.
+ * <li>A <code>Scorer</code> is constructed by {@link #scorer(IndexReader,boolean,boolean)}.
+ * </ol>
+ *
+ * @since 2.9
+ */
+public abstract class Weight implements Serializable {
+
+ /**
+ * An explanation of the score computation for the named document.
+ *
+ * @param reader sub-reader containing the give doc
+ * @param doc
+ * @return an Explanation for the score
+ * @throws IOException
+ */
+ public abstract Explanation explain(IndexReader reader, int doc) throws IOException;
+
+ /** The query that this concerns. */
+ public abstract Query getQuery();
+
+ /** The weight for this query. */
+ public abstract float getValue();
+
+ /** Assigns the query normalization factor to this. */
+ public abstract void normalize(float norm);
+
+ /**
+ * Returns a {@link Scorer} which scores documents in/out-of order according
+ * to <code>scoreDocsInOrder</code>.
+ * <p>
+ * <b>NOTE:</b> even if <code>scoreDocsInOrder</code> is false, it is
+ * recommended to check whether the returned <code>Scorer</code> indeed scores
+ * documents out of order (i.e., call {@link #scoresDocsOutOfOrder()}), as
+ * some <code>Scorer</code> implementations will always return documents
+ * in-order.<br>
+ * <b>NOTE:</b> null can be returned if no documents will be scored by this
+ * query.
+ *
+ * @param reader
+ * the {@link IndexReader} for which to return the {@link Scorer}.
+ * @param scoreDocsInOrder
+ * specifies whether in-order scoring of documents is required. Note
+ * that if set to false (i.e., out-of-order scoring is required),
+ * this method can return whatever scoring mode it supports, as every
+ * in-order scorer is also an out-of-order one. However, an
+ * out-of-order scorer may not support {@link Scorer#nextDoc()}
+ * and/or {@link Scorer#advance(int)}, therefore it is recommended to
+ * request an in-order scorer if use of these methods is required.
+ * @param topScorer
+ * if true, {@link Scorer#score(Collector)} will be called; if false,
+ * {@link Scorer#nextDoc()} and/or {@link Scorer#advance(int)} will
+ * be called.
+ * @return a {@link Scorer} which scores documents in/out-of order.
+ * @throws IOException
+ */
+ public abstract Scorer scorer(IndexReader reader, boolean scoreDocsInOrder,
+ boolean topScorer) throws IOException;
+
+ /** The sum of squared weights of contained query clauses. */
+ public abstract float sumOfSquaredWeights() throws IOException;
+
+ /**
+ * Returns true iff this implementation scores docs only out of order. This
+ * method is used in conjunction with {@link Collector}'s
+ * {@link Collector#acceptsDocsOutOfOrder() acceptsDocsOutOfOrder} and
+ * {@link #scorer(org.apache.lucene.index.IndexReader, boolean, boolean)} to
+ * create a matching {@link Scorer} instance for a given {@link Collector}, or
+ * vice versa.
+ * <p>
+ * <b>NOTE:</b> the default implementation returns <code>false</code>, i.e.
+ * the <code>Scorer</code> scores documents in-order.
+ */
+ public boolean scoresDocsOutOfOrder() { return false; }
+
+}
fnp / pylucene.git / blobdiff