ElasticSearch备考 -- 查询模版

一、题目

### 基础版

Create a search template for the above query, so that the template

(i) is named "with_response_and_tag",

(ii) has a parameter "with_min_response" to represent the lower bound of the `response` field,

(iii) has a parameter "with_max_response" to represent the upper bound of the `response` field,

(iv) has a parameter "with_tag" to represent a possible value of the `tags` field

Test the "with_response_and_tag" search template by setting the

parameters as follows:

(i) "with_min_response": 400,

(ii) "with_max_response": 500

(iii) "with_tag": "security"

### 进阶版

Update the "with_response_and_tag" search template, so that

(i) if the "with_max_response" parameter is not set, then don't set an upper bound to the `response` value, and

(ii) if the "with_tag" parameter is not set, then do not apply that filter at all

Test the "with_response_and_tag" search template by setting only the "with_min_response" parameter to 500

Test the "with_response_and_tag" search template by setting the parameters as follows:

(i) "with_min_response": 500,

(ii) "with_tag": "security"

二、思考

此题主要考察的是查询模版，这在日常工作中用到的比较少，需要注意写法和格式。如下是官方API提供一个模版样例，可以参照这个进行改造查询模版。此外创建模版后要注意验证模版，因为创建模版成功并不代表可以正常执行。

PUT _scripts/my-search-template
{
  "script": {
    "lang": "mustache",
    "source": {
      "query": {
        "match": {
          "message": "{{query_string}}"
        }
      },
      "from": "{{from}}",
      "size": "{{size}}"
    }
  }
}

三、解题

Step 1、【基础版】创建模版

PUT _scripts/with_response_and_tag
{
  "script": {
    "lang": "mustache",
    "source": {
      "query": {
        "range": {
          "response": {
            "gte": "{{with_max_response}}",
            "lte": "{{with_min_response}}"
          }
        },
        "match": {
          "tags": "{{with_tag}}"
        }
      }
    }
  }
}

Step 2、【基础版】验证模版

POST _render/template
{
  "id": "with_response_and_tag",
  "params": {
    "with_max_response": "500",
    "with_min_response": "400",
    "with_tag":"security"
  }
}

Step 3、【基础版】执行模版查询

GET my-index/_search/template
{
  "id": "with_response_and_tag",
  "params": {
    "with_max_response": "500",
    "with_min_response": "400",
    "with_tag":"security"
  }
}

Step 4、【进阶版】更新模版

这里有几点需要注意

source里可以使用三引号包裹，这样就可以不使用转移符
如果参数中有使用条件，则使用 {{#condition}}content{{/condition}}，外面不要引号
如果是if else判断条件，则使用 {{#condition}}if content{{/condition}} {{^condition}}else content{{/condition}}，外面不带引号
默认值方式，{{my-var}}{{^my-var}}default value{{/my-var}}，外面需要引号

PUT _scripts/with_response_and_tag
{
  "script": {
    "lang": "mustache",
    "source": """
      {
        "query": {
            "bool": {
              "filter": [
                {
                  "range": {
                    "response": {
                      "gte": "{{with_min_response}}"
                      {{#with_max_response}}
                      ,"lte": "{{with_max_response}}"
                      {{/with_max_response}}
                    }
                  }
                }, 
                {
                  {{#with_tag}}
                  "match": {
                    "tags":"{{with_tag}}"
                  }  
                  {{/with_tag}}
                }
            ]
          }
        }
      }
    """
  }
}

四、总结

查询模版，这在日常工作中用到的比较少，需要注意写法和格式，多联系
参数外层需要通过双引号包裹，"{{param}}"
不用包裹双引号的有：
- {{#toJson}}tags{{/toJson}}
- {{#condition}}content{{/condition}}
- {#condition}}if content{{/condition}} {{^condition}}else content{{/condition}}