# Validate API
**validate API**允许用户验证一个可能复杂（expensive）的查询而不执行它。我们将使用以下测试数据来解释\_validate：
```
PUT twitter/tweet/_bulk?refresh
{"index":{"_id":1}}
{"user" : "kimchy", "post_date" : "2009-11-15T14:12:12", "message" : "trying out Elasticsearch"}
{"index":{"_id":2}}
{"user" : "kimchi", "post_date" : "2009-11-15T14:12:13", "message" : "My username is similar to @kimchy!"}
```
当发送一个有效查询时：
```
GET twitter/_validate/query?q=user:foo
```
响应包含有效：true：
```
{"valid":true,"_shards":{"total":1,"successful":1,"failed":0}}
```
## Request Parameters
当执行查询使用查询参数q时，传递的查询是使用Lucene查询解析器的查询字符串。还有其他可以传递的参数：
| Name | Description |
| -------------------------- | ----------------------------------------------------- |
| `df` | 在查询中未定义字段前缀时使用的默认字段。 |
| `analyzer` | 分析查询字符串时使用的分析器名称。 |
| `default_operator` | 要使用的默认运算符，可以是**AND**或**OR**。默认为**OR**。 |
| `lenient` | 如果设置为**true**将导致基于格式的失败（例如向数字字段提供文本）被忽略。默认为**false**。 |
| `lowercase_expanded_terms` | 术语是否自动小写，默认为**true**。 |
| `analyze_wildcard` | 是否分析通配符和前缀查询。默认为false。 |
查询也可以在请求主体中发送：
```
GET twitter/tweet/_validate/query
{
"query" : {
"bool" : {
"must" : {
"query_string" : {
"query" : "*:*"
}
},
"filter" : {
"term" : { "user" : "kimchy" }
}
}
}
}
```
> 注意
>
> 在正文中发送的查询必须嵌套在查询键中，与**Search API**相同。
如果查询无效，则`返回信息中 valid`将为 false。在这里，查询无效，因为**Elasticsearch**知道post\_date字段应该是动态映射的日期，foo无法正确解析为日期：
```
GET twitter/tweet/_validate/query?q=post_date:foo
{"valid":false,"_shards":{"total":1,"successful":1,"failed":0}}
```
可以指定**explain**参数以获取有关查询失败原因的更详细信息：
```
GET twitter/tweet/_validate/query?q=post_date:foo&explain=true
```
响应是：
```
{
"valid" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"failed" : 0
},
"explanations" : [ {
"index" : "twitter",
"valid" : false,
"error" : "twitter/IAEc2nIXSSunQA_suI0MLw] QueryShardException[failed to create query:...failed to parse date field [foo]"
} ]
}
```
当查询有效时，**explanations**默认为该查询的字符串表示形式。 将**rewrite**设置为**true**时，**explanations**将更详细地显示将要执行的实际Lucene查询。
模糊查询（**Fuzzy Queries**）：
```
GET twitter/tweet/_validate/query?rewrite=true
{
"query": {
"match": {
"user": {
"query": "kimchy",
"fuzziness": "auto"
}
}
}
}
```
响应：
```
{
"valid": true,
"_shards": {
"total": 1,
"successful": 1,
"failed": 0
},
"explanations": [
{
"index": "twitter",
"valid": true,
"explanation": "+user:kimchy +user:kimchi^0.75 #(ConstantScore(_type:tweet))^0.0"
}
]
}
```
相似度查询（**More Like This**）：
```
GET twitter/tweet/_validate/query?rewrite=true
{
"query": {
"more_like_this": {
"like": {
"_id": "2"
},
"boost_terms": 1
}
}
}
```
响应：
```
{
"valid": true,
"_shards": {
"total": 1,
"successful": 1,
"failed": 0
},
"explanations": [
{
"index": "twitter",
"valid": true,
"explanation": "((user:terminator^3.71334 plot:future^2.763601 plot:human^2.8415773 plot:sarah^3.4193945 plot:kyle^3.8244398 plot:cyborg^3.9177752 plot:connor^4.040236 plot:reese^4.7133346 ... )~6) -ConstantScore(_uid:tweet#2)) #(ConstantScore(_type:tweet))^0.0"
}
]
}
```
> 警告
>
> 请求只在单个分片上执行，这是随机选择的。查询的详细解释可以取决于哪个分片被命中，并且因此可以从一个请求到另一个请求而变化。
---
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```
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```
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