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| <h1 id="Lucene_Net_Sandbox_Queries" data-uid="Lucene.Net.Sandbox.Queries" class="text-break">Namespace Lucene.Net.Sandbox.Queries |
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| <p>Additional queries (some may have caveats or limitations)</p> |
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| <div class="markdown level0 conceptual"></div> |
| <div class="markdown level0 remarks"></div> |
| <h3 id="classes">Classes |
| </h3> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.DuplicateFilter.html">DuplicateFilter</a></h4> |
| <section><p>Filter to remove duplicate values from search results. |
| <p> |
| WARNING: for this to work correctly, you may have to wrap |
| your reader as it cannot current deduplicate across different |
| index segments.</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.FuzzyLikeThisQuery.html">FuzzyLikeThisQuery</a></h4> |
| <section><p>Fuzzifies ALL terms provided as strings and then picks the best n differentiating terms. |
| In effect this mixes the behaviour of <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.FuzzyQuery.html">FuzzyQuery</a> and MoreLikeThis but with special consideration |
| of fuzzy scoring factors. |
| This generally produces good results for queries where users may provide details in a number of |
| fields and have no knowledge of boolean query syntax and also want a degree of fuzzy matching and |
| a fast query. |
| <p> |
| For each source term the fuzzy variants are held in a <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.BooleanQuery.html">BooleanQuery</a> with no coord factor (because |
| we are not looking for matches on multiple variants in any one doc). Additionally, a specialized |
| <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.TermQuery.html">TermQuery</a> is used for variants and does not use that variant term's IDF because this would favour rarer |
| terms eg misspellings. Instead, all variants use the same IDF ranking (the one for the source query |
| term) and this is factored into the variant's boost. If the source query term does not exist in the |
| index the average IDF of the variants is used.</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.SlowFuzzyQuery.html">SlowFuzzyQuery</a></h4> |
| <section><p>Implements the classic fuzzy search query. The similarity measurement |
| is based on the Levenshtein (edit distance) algorithm. |
| <p> |
| Note that, unlike <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.FuzzyQuery.html">FuzzyQuery</a>, this query will silently allow |
| for a (possibly huge) number of edit distances in comparisons, and may |
| be extremely slow (comparing every term in the index).</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.SlowFuzzyTermsEnum.html">SlowFuzzyTermsEnum</a></h4> |
| <section><p>Potentially slow fuzzy <span class="xref">Lucene.Net.Index.TermsEnum</span> for enumerating all terms that are similar |
| to the specified filter term. |
| <p> |
| If the minSimilarity or maxEdits is greater than the Automaton's |
| allowable range, this backs off to the classic (brute force) |
| fuzzy terms enum method by calling <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Search.FuzzyTermsEnum.html#Lucene_Net_Search_FuzzyTermsEnum_GetAutomatonEnum_System_Int32_Lucene_Net_Util_BytesRef_">GetAutomatonEnum(Int32, BytesRef)</a>. |
| <p> |
| Term enumerations are always ordered by |
| <span class="xref">Lucene.Net.Search.FuzzyTermsEnum.Comparer</span>. Each term in the enumeration is |
| greater than all that precede it.</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.SortedSetSortField.html">SortedSetSortField</a></h4> |
| <section><p>SortField for <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Index.SortedSetDocValues.html">SortedSetDocValues</a>. |
| <p> |
| A <a class="xref" href="http://localhost:8080/api/core/Lucene.Net.Index.SortedSetDocValues.html">SortedSetDocValues</a> contains multiple values for a field, so sorting with |
| this technique "selects" a value as the representative sort value for the document. |
| <p> |
| By default, the minimum value in the set is selected as the sort value, but |
| this can be customized. Selectors other than the default do have some limitations |
| (see below) to ensure that all selections happen in constant-time for performance. |
| <p> |
| Like sorting by string, this also supports sorting missing values as first or last, |
| via <a class="xref" href="Lucene.Net.Sandbox.Queries.SortedSetSortField.html#Lucene_Net_Sandbox_Queries_SortedSetSortField_MissingValue">MissingValue</a>. |
| <p> |
| Limitations: |
| <ul><li> |
| Fields containing <span class="xref">System.Int32.MaxValue</span> or more unique values |
| are unsupported. |
| </li><li> |
| Selectors other than the default <a class="xref" href="Lucene.Net.Sandbox.Queries.Selector.html#Lucene_Net_Sandbox_Queries_Selector_MIN">MIN</a> require |
| optional codec support. However several codecs provided by Lucene, |
| including the current default codec, support this. |
| </li></ul></p> |
| </section> |
| <h3 id="enums">Enums |
| </h3> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.KeepMode.html">KeepMode</a></h4> |
| <section><p>KeepMode determines which document id to consider as the master, all others being |
| identified as duplicates. Selecting the "first occurrence" can potentially save on IO.</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.ProcessingMode.html">ProcessingMode</a></h4> |
| <section><p>"Full" processing mode starts by setting all bits to false and only setting bits |
| for documents that contain the given field and are identified as none-duplicates. |
| <p> |
| "Fast" processing sets all bits to true then unsets all duplicate docs found for the |
| given field. This approach avoids the need to read DocsEnum for terms that are seen |
| to have a document frequency of exactly "1" (i.e. no duplicates). While a potentially |
| faster approach , the downside is that bitsets produced will include bits set for |
| documents that do not actually contain the field given.</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Sandbox.Queries.Selector.html">Selector</a></h4> |
| <section><p>Selects a value from the document's set to use as the sort value</p> |
| </section> |
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