加载Elasticsearch Nest查询中的特定字段

问题描述

文档似乎表明我可以返回一个字段的子集而不是整个文档。这是我的代码：

the documentation seems to indicate i can return a subset of fields instead of the entire document. here's my code:

var result = client.Search<MyObject>(s => s
                .Fields(f => f.Title)
                .Query(q => q
                    .QueryString(qs => qs
                        .OnField("title")
                        .Query("the"))));

我正在'标题'字段上搜索'''，想要刚刚返回'标题'。我的结果。文档对象包含10个对象，每个对象都是空的。

i'm searching on the word 'the' on the 'title' field and wanting to just return 'title'. my result.Documents object contains 10 objects that are each null.

我看到我想要的值，但它在搜索响应中很深：
result.Hits [0] .Fields.FieldValues [0] ...

i do see the values i want but it's deep in the search response:result.Hits[0].Fields.FieldValues[0]...

有更好的方法来获取返回的'title'字段列表吗？ strong>

is there a better way to get at the list of 'title' fields returned?

我的数据映射（截断）是这个...

my mapping for the data (truncated) is this ...

{
   "myidex": {
      "mappings": {
         "myobject": {
            "properties": {
               "title": {
                  "type": "string"
               },
               "artists": {
                  "properties": {
                     "id": {
                        "type": "string",
                        "index": "not_analyzed",
                        "analyzer": "fullTerm"
                     },
                     "name": {
                        "type": "string",
                        "index": "not_analyzed",
                        "analyzer": "fullTerm"
                     }
                  }
               }
            }
         }
      }
   }
}

我的类对象如下所示：

[Table("MyTable")]
[Serializable]
[ElasticType(Name="myobject")]
public class MyObject
{
    [ElasticProperty]
    public string Title { get; set; }

    [JsonIgnore]
    public string Artistslist { get; set; }
    [ElasticProperty(Analyzer = "caseInsensitive")]
    public List<Person> Artists { get; set; }
}

[Serializable]
public class Person
{
    [ElasticProperty(Analyzer = "fullTerm", Index = FieldIndexOption.not_analyzed)]
    public string Name { get; set; }
    [ElasticProperty(Analyzer = "fullTerm", Index = FieldIndexOption.not_analyzed)]
    public string Id { get; set; }
}

艺术家列表来自我的数据源（sql），然后我将其解析成在索引数据之前，一个新的List对象。

Artistslist comes from my data source (sql) then i parse it out into a new List object before indexing the data.

推荐答案

我认为这个深层嵌套的价值是对Elasticsearch 1.0的改变以及如何部分字段现在作为数组返回（请参阅）。这在文档中得到解决。在 Fields（）vs SourceIncludes（）部分。它显示了使用 FieldValue 助手方法来访问这些值的示例。基于此，请尝试以下操作：

I think this deeply nested value is do to a change in Elasticsearch 1.0 and how partial fields are now returned as arrays (See 1.0 Breaking Changes - Return Values for details.). This is addressed in the NEST 1.0 Breaking Changes documentation; in the Fields() vs SourceIncludes() section. It shows an example of using a FieldValue helper method to gain access to these values. Based on that, try the following:

对于所有项目：

 foreach (var hit in result.Hits)
 {
     var title = hit.Fields.FieldValue<MyObject, string>(f => f.Title);
 }

对于特定项目：

 var title = result.Hits.ElementAt(0)
                  .Fields.FieldValue<MyObject, string>(f => f.Title);

我知道它仍然有点冗长，但它应该适用于您，并将处理新的数组返回Elasticsearch 1.0的格式化。

I know it is still a bit verbose but it should work for you and will handle the new array return formatting of Elasticsearch 1.0.

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