> For the complete documentation index, see [llms.txt](https://xiaoxiami.gitbook.io/elasticsearch/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://xiaoxiami.gitbook.io/elasticsearch/ji-chu/mapping/323mapping-parametersff08-ying-she-can-shu-ff09/3234coerceff08-qiang-zhi-lei-xing-zhuan-huan-ff09.md).

# Coerce（强制类型转换）

数据不总是干净的.根据它的生成方式,一个数字可能会在 `JSON body`中呈现为一个真正的 **JSON** 数字。例如5,但它也可能呈现为字符串,例如 **"5"** 。或者,应该是整型的数字被替代地呈现为浮点型.例如, **5.0** 或者**"5.0"**.

`Coercion`尝试着清理脏数据让字段符合相应的数据类型.例如 :

* 字符串被强制转换为数字.
* 浮点型被截断为整型.

例如**:**

```
curl -XPUT 'localhost:9200/my_index?pretty' -H 'Content-Type: application/json' -d'
{
  "mappings": {
    "my_type": {
      "properties": {
        "number_one": {
          "type": "integer"
        },
        "number_two": {
          "type": "integer",
          "coerce": false
        }
      }
    }
  }
}
'
curl -XPUT 'localhost:9200/my_index/my_type/1?pretty' -H 'Content-Type: application/json' -d'
{
  "number_one": "10"  # 1
}
'
curl -XPUT 'localhost:9200/my_index/my_type/2?pretty' -H 'Content-Type: application/json' -d'
{
  "number_two": "10"  # 2
}
'
```

| 1 | `number_one` 字段会包含整型 `10`.                        |
| - | ------------------------------------------------- |
| 2 | `document`（文档）会拒绝因为`coercion`是关闭的,所以无法将字符串转换成整数型. |

> 提醒：
>
> **coerce** 配置允许在相同的索引中具有相同名称的字段有不同的配置.可以通过[PUT mapping API](https://www.elastic.co/guide/en/elasticsearch/reference/5.3/indices-put-mapping.html)来更新已存在字段上的 **coerce** 值.

## Index-level default（索引级别的默认参数） <a href="#coerce-qiang-zhi-lei-xing-zhuan-huan-indexleveldefault-suo-yin-ji-bie-de-mo-ren-can-shu" id="coerce-qiang-zhi-lei-xing-zhuan-huan-indexleveldefault-suo-yin-ji-bie-de-mo-ren-can-shu"></a>

`index.mapping.coerce`配置可以在**index level**（索引级别）来设置,以便在所有的`Mapping Types` 全局关闭`coercion配置`.

```
curl -XPUT 'localhost:9200/my_index?pretty' -H 'Content-Type: application/json' -d'
{
  "settings": {
    "index.mapping.coerce": false
  },
  "mappings": {
    "my_type": {
      "properties": {
        "number_one": {
          "type": "integer",
          "coerce": true
        },
        "number_two": {
          "type": "integer"
        }
      }
    }
  }
}
'
curl -XPUT 'localhost:9200/my_index/my_type/1?pretty' -H 'Content-Type: application/json' -d'
{ "number_one": "10" } # 1
'
curl -XPUT 'localhost:9200/my_index/my_type/2?pretty' -H 'Content-Type: application/json' -d'
{ "number_two": "10" } # 2
'
```

| 1 | `number_one` 字段覆盖了**index level**（索引级别）的设置并开启了 `coercion`.                |
| - | ------------------------------------------------------------------------- |
| 2 | `document`（文档）会拒绝请求,因为 `number_two` 字段继承了 `index-level（索引级别）coercion`的设置. |


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