| using Lucene.Net.Search; |
| using System; |
| using System.IO; |
| |
| namespace Lucene.Net.Join |
| { |
| /* |
| * 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. |
| */ |
| |
| /// <summary> |
| /// Utility for query time joining using <see cref="TermsQuery"/> and <see cref="TermsCollector"/>. |
| /// |
| /// @lucene.experimental |
| /// </summary> |
| public sealed class JoinUtil |
| { |
| // No instances allowed |
| private JoinUtil() |
| { |
| } |
| |
| /// <summary> |
| /// Method for query time joining. |
| /// <para/> |
| /// Execute the returned query with a <see cref="IndexSearcher"/> to retrieve all documents that have the same terms in the |
| /// to field that match with documents matching the specified <paramref name="fromQuery"/> and have the same terms in the from field. |
| /// <para/> |
| /// In the case a single document relates to more than one document the <paramref name="multipleValuesPerDocument"/> option |
| /// should be set to true. When the <paramref name="multipleValuesPerDocument"/> is set to <c>true</c> only the |
| /// the score from the first encountered join value originating from the 'from' side is mapped into the 'to' side. |
| /// Even in the case when a second join value related to a specific document yields a higher score. Obviously this |
| /// doesn't apply in the case that <see cref="ScoreMode.None"/> is used, since no scores are computed at all. |
| /// <para/> |
| /// Memory considerations: During joining all unique join values are kept in memory. On top of that when the <paramref name="scoreMode"/> |
| /// isn't set to <see cref="ScoreMode.None"/> a float value per unique join value is kept in memory for computing scores. |
| /// When <paramref name="scoreMode"/> is set to <see cref="ScoreMode.Avg"/> also an additional integer value is kept in memory per unique |
| /// join value. |
| /// </summary> |
| /// <param name="fromField"> The from field to join from </param> |
| /// <param name="multipleValuesPerDocument"> Whether the from field has multiple terms per document </param> |
| /// <param name="toField"> The to field to join to </param> |
| /// <param name="fromQuery"> The query to match documents on the from side </param> |
| /// <param name="fromSearcher"> The searcher that executed the specified <paramref name="fromQuery"/> </param> |
| /// <param name="scoreMode"> Instructs how scores from the <paramref name="fromQuery"/> are mapped to the returned query </param> |
| /// <returns>A <see cref="Query"/> instance that can be used to join documents based on the terms in the from and to field</returns> |
| /// <exception cref="IOException"> If I/O related errors occur </exception> |
| public static Query CreateJoinQuery(string fromField, bool multipleValuesPerDocument, string toField, Query fromQuery, IndexSearcher fromSearcher, ScoreMode scoreMode) |
| { |
| switch (scoreMode) |
| { |
| case ScoreMode.None: |
| TermsCollector termsCollector = TermsCollector.Create(fromField, multipleValuesPerDocument); |
| fromSearcher.Search(fromQuery, termsCollector); |
| return new TermsQuery(toField, fromQuery, termsCollector.CollectorTerms); |
| case ScoreMode.Total: |
| case ScoreMode.Max: |
| case ScoreMode.Avg: |
| TermsWithScoreCollector termsWithScoreCollector = TermsWithScoreCollector.Create(fromField, multipleValuesPerDocument, scoreMode); |
| fromSearcher.Search(fromQuery, termsWithScoreCollector); |
| return new TermsIncludingScoreQuery(toField, multipleValuesPerDocument, termsWithScoreCollector.CollectedTerms, termsWithScoreCollector.ScoresPerTerm, fromQuery); |
| default: |
| throw new ArgumentException(string.Format("Score mode {0} isn't supported.", scoreMode)); |
| } |
| } |
| } |
| } |