[英]Lucene.net: No search results when using MultiFieldQueryParser
我正在使用Lucene.Net 4.8.0版和 .NET Core 3.1。 在下面的示例代碼中,我編寫了一個新索引並向其中添加了三個文檔。 每個文檔都包含ProjectName
、 Customer
和Country
字段。
當我解析查詢"Germany"
時,搜索返回 2 個命中,以查找在其任何字段中包含單詞 "Germany" 的文檔。 但是,當我解析查詢"Country:Germany"
時,搜索返回 0 個命中,盡管其Country
字段中顯然有一個值為 "Germany" 的文檔。
我究竟做錯了什么?
我還通過 Luke 工具( https://github.com/DmitryKey/luke/releases/tag/4.8.0 )檢查了我的索引。 使用 Luke,搜索對於相同的索引目錄工作正常。
我的 C# 代碼在這里:
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");
}
}
}
我發現了我犯的錯誤。 顯然,Lucene 中的字段名稱是區分大小寫的。 因此,在我的例子中,代碼queryString.ToLowerInvariant()
將查詢字符串"Country:Germany"
轉換為"country:Germany"
,因此沒有找到任何內容,因為小寫字段country
不存在。
解決方案:刪除對ToLowerInvariant()
的調用。
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