# Get

要从Elasticsearch中获取文档，我们需要使用同样的`_index`，`_type`以及 `_id`但是不同的HTTP变量`GET`：

```javascript
GET /website/blog/123?pretty
```

返回结果包含了之前提到的内容，以及一个新的字段`_source`，它包含我们在最初创建索引时的原始JSON文档。

```javascript
{
  "_index" :   "website",
  "_type" :    "blog",
  "_id" :      "123",
  "_version" : 1,
  "found" :    true,
  "_source" :  {
      "title": "My first blog entry",
      "text":  "Just trying this out..."
      "date":  "2014/01/01"
  }
}
```

> ### `pretty`

在任意的查询字符串中添加`pretty`参数，类似上面的请求，Elasticsearch就可以得到*优美打印*的更加易于识别的JSON结果。`_source`字段不会执行优美打印，它的样子取决于我们录入的样子。

GET请求的返回结果中包含`{"found": true}`。这意味着这篇文档确实被找到了。如果我们请求了一个不存在的文档，我们依然会得到JSON反馈，只是`found`的值会变为`false`。

同样，HTTP返回码也会由`'200 OK'`变为`'404 Not Found'`。我们可以在`curl`后添加`-i`，这样你就能得到反馈头文件：

```javascript
curl -i -XGET /website/blog/124?pretty
```

反馈结果就会是这个样子：

```javascript
HTTP/1.1 404 Not Found
Content-Type: application/json; charset=UTF-8
Content-Length: 83

{
  "_index" : "website",
  "_type" :  "blog",
  "_id" :    "124",
  "found" :  false
}
```

## 检索文档中的一部分

通常，`GET`请求会将整个文档放入`_source`字段中一并返回。但是可能你只需要`title`字段。你可以使用`_source`得到指定字段。如果需要多个字段你可以使用逗号分隔：

```javascript
GET /website/blog/123?_source=title,text
```

现在`_source`字段中就只会显示你指定的字段：

```javascript
{
  "_index" :   "website",
  "_type" :    "blog",
  "_id" :      "123",
  "_version" : 1,
  "exists" :   true,
  "_source" : {
      "title": "My first blog entry" ,
      "text":  "Just trying this out..."
  }
}
```

或者你只想得到`_source`字段而不要其他的元数据，你可以这样请求：

```javascript
GET /website/blog/123/_source
```

这样结果就只返回:

```javascript
{
   "title": "My first blog entry",
   "text":  "Just trying this out...",
   "date":  "2014/01/01"
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://hezhiqiang.gitbook.io/elasticsearch/data/get.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.