使用 Elasticsearch NEST C# 索引 Json 文档

Posted 2023-03-30

【中文标题】使用 Elasticsearch NEST C# 索引 Json 文档

【英文标题】：Index Json Document using Elasticsearch NEST C#

【发布时间】：2016-06-14 18:28:32

【问题描述】：

我是 Elasticsearch 的新手，想知道如何使用 NEST C# 为 Elasticsearch 创建以下 json 文档的索引和索引？

    "BookName": "Book1",
    "ISBN": "978-3-16-148410-0",
    "chapter" : [
        
            "chapter_name": "Chapter1",
            "chapter_desc": "Before getting into computer programming, let us first understand computer programs and what they..."
        ,
        
            "chapter_name": "Chapter2",
            "chapter_desc": "Today computer programs are being used in almost every field, household, agriculture, medical, entertainment, defense.."
        ,
        
            "chapter_name": "Chapter3",
            "chapter_desc": "MS Word, MS Excel, Adobe Photoshop, Internet Explorer, Chrome, etc., are..."
        ,
        
            "chapter_name": "Chapter4",
            "chapter_desc": "Computer programs are being used to develop graphics and special effects in movie..."
        
    ]

【问题讨论】：

github.com/elastic/elasticsearch-net/issues/336

【参考方案1】：

用 NEST 创建索引很简单

var client = new ElasticClient();
client.CreateIndex("index-name");

这将使用为节点定义的默认分片和副本数创建一个索引。

要将表示为 json 的文档索引到索引中

var json = @"
    ""BookName"": ""Book1"",
    ""ISBN"": ""978-3-16-148410-0"",
    ""chapter"" : [
        
            ""chapter_name"": ""Chapter1"",
            ""chapter_desc"": ""Before getting into computer programming, let us first understand computer programs and what they...""
        ,
        
    ""chapter_name"": ""Chapter2"",
            ""chapter_desc"": ""Today computer programs are being used in almost every field, household, agriculture, medical, entertainment, defense..""
        ,
        
    ""chapter_name"": ""Chapter3"",
            ""chapter_desc"": ""MS Word, MS Excel, Adobe Photoshop, Internet Explorer, Chrome, etc., are...""
        ,
        
    ""chapter_name"": ""Chapter4"",
            ""chapter_desc"": ""Computer programs are being used to develop graphics and special effects in movie...""
        
    ]
";

var indexResponse = client.LowLevel.Index<string>("index-name", "type-name", json);

if (!indexResponse.Success)
    Console.WriteLine(indexResponse.DebugInformation);

这里我们使用低级客户端来索引 json，可通过 ElasticClient 上的 .LowLevel 属性在 NEST 中使用。

要搜索索引文档将是

// refresh the index so that newly indexed documents are available
// for search without waiting for the refresh interval
client.Refresh("index-name");

var searchResponse = client.Search<dynamic>(s => s
    .Index("index-name")
    .Type("type-name")
    .Query(q => q
        .Match(m => m
            .Query("Photoshop")
            .Field("chapter.chapter_desc")
        )
    )
);

这将返回索引的文档。这里Search<T>()中使用的泛型类型参数dynamic表示生成的文档会反序列化为Json.Net的JObject类型。

当我们创建索引时，我们没有为我们的类型指定映射，type-name，所以 Elasticsearch 从 json 文档的结构中推断出映射。 This is dynamic mapping 并且在许多情况下都很有用，但是，如果您知道要发送的文档的结构并且不会被破坏性地改变，那么您 specify a mapping for the type。在这个特定示例中这样做的好处是 chapter 数组将被推断为 object type 映射，但如果您想搜索单个章节的章节名称和章节描述，那么您可能想要映射chapter 作为nested type。

【讨论】：

嗨，我尝试使用 NEST 版本 7.10.1。它在 var indexResponse = _elasticClient.LowLevel.Index<string>("index-name", "type-name", json); 处有语法错误。错误是The type 'string' cannot be used as type parameter 'TResponse' in the generic type or method 'IElasticLowLevelClient.Index<TResponse>(string, string, PostData, IndexRequestParameters)'. There is no implicit reference conversion from 'string'

嘿@Steve，自从这个答案以来，客户已经改变了一点。查看elastic.co/guide/en/elasticsearch/client/net-api/current/… 和elastic.co/guide/en/elasticsearch/client/net-api/current/… 中的注释。具体来说，响应类型现在是StringResponse，并且不支持文档类型的_type参数