使用 Elasticsearch NEST C# 索引 Json 文档

Question

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..."
        }
    ]
}

Answer 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。