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| <h1 id="Lucene_Net_Index_Sorter" data-uid="Lucene.Net.Index.Sorter" class="text-break">Namespace Lucene.Net.Index.Sorter |
| </h1> |
| <div class="markdown level0 summary"><!-- |
| Licensed to the Apache Software Foundation (ASF) under one or more |
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| <p>Provides index sorting capablities. The application can use any |
| Sort specification, e.g. to sort by fields using DocValues or FieldCache, or to |
| reverse the order of the documents (by using SortField.Type.DOC in reverse). |
| Multi-level sorts can be specified the same way you would when searching, by |
| building Sort from multiple SortFields.</p> |
| <p><a class="xref" href="Lucene.Net.Index.Sorter.SortingMergePolicy.html">SortingMergePolicy</a> can be used to |
| make Lucene sort segments before merging them. This will ensure that every |
| segment resulting from a merge will be sorted according to the provided |
| <xref:Lucene.Net.Search.Sort>. This however makes merging and |
| thus indexing slower.</p> |
| <p>Sorted segments allow for early query termination when the sort order |
| matches index order. This makes query execution faster since not all documents |
| need to be visited. Please note that this is an expert feature and should not |
| be used without a deep understanding of Lucene merging and document collection.</p> |
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| <div class="markdown level0 conceptual"></div> |
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| <h3 id="classes">Classes |
| </h3> |
| <h4><a class="xref" href="Lucene.Net.Index.Sorter.BlockJoinComparerSource.html">BlockJoinComparerSource</a></h4> |
| <section><p>Helper class to sort readers that contain blocks of documents. |
| <p> |
| Note that this class is intended to used with <a class="xref" href="Lucene.Net.Index.Sorter.SortingMergePolicy.html">SortingMergePolicy</a>, |
| and for other purposes has some limitations: |
| <ul><li>Cannot yet be used with <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.IndexSearcher.html#Lucene_Net_Search_IndexSearcher_SearchAfter_Lucene_Net_Search_ScoreDoc_Lucene_Net_Search_Query_Lucene_Net_Search_Filter_System_Int32_Lucene_Net_Search_Sort_">SearchAfter(ScoreDoc, Query, Filter, Int32, Sort)</a></li><li>Filling sort field values is not yet supported.</li></ul></p> |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div><p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Index.Sorter.EarlyTerminatingSortingCollector.html">EarlyTerminatingSortingCollector</a></h4> |
| <section><p>A <span class="xref">Lucene.Net.Search.ICollector</span> that early terminates collection of documents on a |
| per-segment basis, if the segment was sorted according to the given |
| <span class="xref">Lucene.Net.Search.Sort</span>.</p> |
| <p> |
| <strong>NOTE:</strong> the <span class="xref">Lucene.Net.Search.ICollector</span> detects sorted segments according to |
| <a class="xref" href="Lucene.Net.Index.Sorter.SortingMergePolicy.html">SortingMergePolicy</a>, so it's best used in conjunction with it. Also, |
| it collects up to a specified <a class="xref" href="Lucene.Net.Index.Sorter.EarlyTerminatingSortingCollector.html#Lucene_Net_Index_Sorter_EarlyTerminatingSortingCollector_m_numDocsToCollect">m_numDocsToCollect</a> from each segment, |
| and therefore is mostly suitable for use in conjunction with collectors such as |
| <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.TopDocsCollector-1.html">TopDocsCollector<T></a>, and not e.g. <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.TotalHitCountCollector.html">TotalHitCountCollector</a>. |
| </p> |
| <p> |
| <strong>NOTE</strong>: If you wrap a <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.TopDocsCollector-1.html">TopDocsCollector<T></a> that sorts in the same |
| order as the index order, the returned <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.TopDocsCollector-1.html#Lucene_Net_Search_TopDocsCollector_1_GetTopDocs">GetTopDocs()</a> |
| will be correct. However the total of <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.TopDocsCollector-1.html#Lucene_Net_Search_TopDocsCollector_1_TotalHits">TotalHits</a> |
| hit count will be underestimated since not all matching documents will have |
| been collected. |
| </p> |
| <p> |
| <strong>NOTE</strong>: This <span class="xref">Lucene.Net.Search.ICollector</span> uses <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.Sort.html#Lucene_Net_Search_Sort_ToString">ToString()</a> to detect |
| whether a segment was sorted with the same <span class="xref">Lucene.Net.Search.Sort</span>. This has |
| two implications: |
| <ul> |
| <li>if a custom comparer is not implemented correctly and returns |
| different identifiers for equivalent instances, this collector will not |
| detect sorted segments,</li> |
| <li>if you suddenly change the <span class="xref">Lucene.Net.Index.IndexWriter</span>'s |
| <a class="xref" href="Lucene.Net.Index.Sorter.SortingMergePolicy.html">SortingMergePolicy</a> to sort according to another criterion and if both |
| the old and the new <span class="xref">Lucene.Net.Search.Sort</span>s have the same identifier, this |
| <span class="xref">Lucene.Net.Search.ICollector</span> will incorrectly detect sorted segments.</li> |
| </ul> |
| |
| @lucene.experimental |
| </p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Index.Sorter.SortingAtomicReader.html">SortingAtomicReader</a></h4> |
| <section><p>An <span class="xref">Lucene.Net.Index.AtomicReader</span> which supports sorting documents by a given |
| <span class="xref">Lucene.Net.Search.Sort</span>. You can use this class to sort an index as follows:</p> |
| <pre><code>IndexWriter writer; // writer to which the sorted index will be added |
| DirectoryReader reader; // reader on the input index |
| Sort sort; // determines how the documents are sorted |
| AtomicReader sortingReader = SortingAtomicReader.Wrap(SlowCompositeReaderWrapper.Wrap(reader), sort); |
| writer.AddIndexes(reader); |
| reader.Dispose(); // alternatively, you can use a using block |
| writer.Dispose(); // alternatively, you can use a using block</code></pre> |
| |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Index.Sorter.SortingMergePolicy.html">SortingMergePolicy</a></h4> |
| <section><p>A <span class="xref">Lucene.Net.Index.MergePolicy</span> that reorders documents according to a <span class="xref">Lucene.Net.Search.Sort</span> |
| before merging them. As a consequence, all segments resulting from a merge |
| will be sorted while segments resulting from a flush will be in the order |
| in which documents have been added. |
| <p><strong>NOTE</strong>: Never use this policy if you rely on |
| <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Index.IndexWriter.html#Lucene_Net_Index_IndexWriter_AddDocuments_System_Collections_Generic_IEnumerable_System_Collections_Generic_IEnumerable_Lucene_Net_Index_IIndexableField___Lucene_Net_Analysis_Analyzer_">AddDocuments(IEnumerable<IEnumerable<IIndexableField>>, Analyzer)</a> |
| to have sequentially-assigned doc IDs, this policy will scatter doc IDs. |
| </p> |
| <p><strong>NOTE</strong>: This policy should only be used with idempotent <span class="xref">Lucene.Net.Search.Sort</span>s |
| so that the order of segments is predictable. For example, using |
| <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.Sort.html#Lucene_Net_Search_Sort_INDEXORDER">INDEXORDER</a> in reverse (which is not idempotent) will make |
| the order of documents in a segment depend on the number of times the segment |
| has been merged.</p> |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div><p> |
| </p></p> |
| </section> |
| </article> |
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