为什么这个 Lucene.Net 查询失败？

Question

我正在尝试转换我的搜索功能以允许涉及多个单词的模糊搜索。我现有的搜索代码如下所示：

        // Split the search into seperate queries per word, and combine them into one major query
        var finalQuery = new BooleanQuery();

        string[] terms = searchString.Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries);
        foreach (string term in terms)
        {
            // Setup the fields to search
            string[] searchfields = new string[] 
            {
                // Various strings denoting the document fields available
            };

            var parser = new MultiFieldQueryParser(Lucene.Net.Util.Version.LUCENE_29, searchfields, new StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_29));
            finalQuery.Add(parser.Parse(term), BooleanClause.Occur.MUST);
        }

        // Perform the search
        var directory = FSDirectory.Open(new DirectoryInfo(LuceneIndexBaseDirectory));
        var searcher = new IndexSearcher(directory, true);
        var hits = searcher.Search(finalQuery, MAX_RESULTS);

这可以正常工作，如果我有一个名称字段为“我的名字是 Andrew”的实体，并且我执行搜索“Andrew Name”，Lucene 会正确找到正确的文档。现在我想启用模糊搜索，以便正确找到“Anderw Name”。我更改了方法以使用以下代码：

        const int MAX_RESULTS = 10000;
        const float MIN_SIMILARITY = 0.5f;
        const int PREFIX_LENGTH = 3;

        if (string.IsNullOrWhiteSpace(searchString))
            throw new ArgumentException("Provided search string is empty");

        // Split the search into seperate queries per word, and combine them into one major query
        var finalQuery = new BooleanQuery();

        string[] terms = searchString.Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries);
        foreach (string term in terms)
        {
            // Setup the fields to search
            string[] searchfields = new string[] 
            {
                // Strings denoting document field names here
            };

            // Create a subquery where the term must match at least one of the fields
            var subquery = new BooleanQuery();
            foreach (string field in searchfields)
            {
                var queryTerm = new Term(field, term);
                var fuzzyQuery = new FuzzyQuery(queryTerm, MIN_SIMILARITY, PREFIX_LENGTH);
                subquery.Add(fuzzyQuery, BooleanClause.Occur.SHOULD);
            }

            // Add the subquery to the final query, but make at least one subquery match must be found
            finalQuery.Add(subquery, BooleanClause.Occur.MUST);
        }

        // Perform the search
        var directory = FSDirectory.Open(new DirectoryInfo(LuceneIndexBaseDirectory));
        var searcher = new IndexSearcher(directory, true);
        var hits = searcher.Search(finalQuery, MAX_RESULTS);

不幸的是，使用此代码，如果我提交搜索查询“Andrew Name”（与以前相同），我会得到零结果。

核心思想是所有术语必须至少在一个文档字段中找到，但每个术语可以驻留在不同的字段中。有谁知道为什么我重写的查询失败？

---

Final Edit: Ok it turns out I was over complicating this by a LOT, and there was no need to change from my first approach. After reverting back to the first code snippet, I enabled fuzzy searching by changing

finalQuery.Add(parser.Parse(term), BooleanClause.Occur.MUST);

到

finalQuery.Add(parser.Parse(term.Replace("~", "") + "~"), BooleanClause.Occur.MUST);

Answer 1

如果我将 searchString 重写为小写，您的代码对我有用。我假设您在索引时使用 StandardAnalyzer，并且它将生成小写术语。

您需要 1) 将令牌传递给相同的分析器（以启用相同的处理），2) 应用与分析器相同的逻辑，或 3) 使用与您执行的处理相匹配的分析器 (WhitespaceAnalyzer) 。

Answer 2

您希望这一行：

var queryTerm = new Term(term);

看起来像这样：

var queryTerm = new Term(field, term);

现在您正在搜索字段 term （可能不存在）中的空字符串（永远不会找到）。