[英]Lucene.net: No search results when using MultiFieldQueryParser
I am using Lucene.Net version 4.8.0 with .NET Core 3.1.我正在使用Lucene.Net 4.8.0版和 .NET Core 3.1。 In the sample code below, I write a new index and add three documents to it.
在下面的示例代码中,我编写了一个新索引并向其中添加了三个文档。 Each document contains the fields
ProjectName
, Customer
and Country
.每个文档都包含
ProjectName
、 Customer
和Country
字段。
When I parse the query "Germany"
, the search returns 2 hits for documents that contain the word "Germany" in any of its fields.当我解析查询
"Germany"
时,搜索返回 2 个命中,以查找在其任何字段中包含单词 "Germany" 的文档。 However, when I parse the query "Country:Germany"
, the search returns 0 hits, although there clearly is a document with the value "Germany" in its Country
field.但是,当我解析查询
"Country:Germany"
时,搜索返回 0 个命中,尽管其Country
字段中显然有一个值为 "Germany" 的文档。
What am I doing wrong?我究竟做错了什么?
I also checked my index by means of the Luke tool ( https://github.com/DmitryKey/luke/releases/tag/4.8.0 ).我还通过 Luke 工具( https://github.com/DmitryKey/luke/releases/tag/4.8.0 )检查了我的索引。 With Luke, the search works fine for the same index directory.
使用 Luke,搜索对于相同的索引目录工作正常。
My C# code is here:我的 C# 代码在这里:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Documents;
using Lucene.Net.Index;
using Lucene.Net.QueryParsers.Classic;
using Lucene.Net.Search;
using Lucene.Net.Store;
using Lucene.Net.Util;
using Directory = System.IO.Directory;
namespace LuceneTestApp
{
class Program
{
static string CreateTestIndex()
{
string indexDir = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString());
if(Directory.Exists(indexDir))
throw new IOException("Random index directory already exists. Please try again.");
using var dir = FSDirectory.Open(indexDir);
using var analyzer = new StandardAnalyzer(LuceneVersion.LUCENE_48);
var indexConfig = new IndexWriterConfig(LuceneVersion.LUCENE_48, analyzer);
using var writer = new IndexWriter(dir, indexConfig);
AddDocumentTo(writer, "AwesomeProject_1", "Volkswagen", "Germany");
AddDocumentTo(writer, "AwesomeProject_2", "Ford", "USA");
AddDocumentTo(writer, "AwesomeProject_3", "Audi Germany", "France");
writer.Commit();
return indexDir;
}
static void AddDocumentTo(IndexWriter writer, string projectName, string customer, string country)
{
var doc = new Document();
doc.Add(new StringField( "ProjectName", projectName, Field.Store.YES));
doc.Add(new TextField( "Customer", customer, Field.Store.YES));
doc.Add(new TextField( "Country", country, Field.Store.YES));
writer.AddDocument(doc);
}
static IList<string> Search(string indexDir, string queryString)
{
using var dir = FSDirectory.Open(indexDir);
using var reader = DirectoryReader.Open(dir);
using var analyzer = new StandardAnalyzer(LuceneVersion.LUCENE_48);
var searcher = new IndexSearcher(reader);
string[] searchFields = {"ProjectName", "Customer", "Country"};
var queryParser = new MultiFieldQueryParser(LuceneVersion.LUCENE_48, searchFields, analyzer);
queryParser.DefaultOperator = Operator.AND;
var query = queryParser.Parse(queryString.ToLowerInvariant());
int maxNumHits = 10;
var topDocs = searcher.Search(query, maxNumHits);
return topDocs.ScoreDocs.Select(hit => $"Score {hit.Score,5:0.000} DocId {hit.Doc}").ToList();
}
static void Main(string[] args)
{
Console.WriteLine("=================");
string indexDir = CreateTestIndex();
IList<string> hitsOne = Search(indexDir, "Germany");
IList<string> hitsTwo = Search(indexDir, "Country:Germany");
Console.WriteLine($"Search one yields {hitsOne.Count} hits.");
Console.WriteLine($"Search two yields {hitsTwo.Count} hits.");
Console.WriteLine("=================\n\n");
}
}
}
I found the mistake I made.我发现了我犯的错误。 Apparently, field names in Lucene are case-sensitive.
显然,Lucene 中的字段名称是区分大小写的。 Hence, in my case the code
queryString.ToLowerInvariant()
turned the query string "Country:Germany"
into "country:Germany"
and, thus, nothing was found, because the lower-case field country
does not exist.因此,在我的例子中,代码
queryString.ToLowerInvariant()
将查询字符串"Country:Germany"
转换为"country:Germany"
,因此没有找到任何内容,因为小写字段country
不存在。
Solution: Remove the call to ToLowerInvariant()
.解决方案:删除对
ToLowerInvariant()
的调用。
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