Elasticsearch学习笔记：MUST

elasticsearch：6.7

如下：

POST players/players/_search
{
   "query": {
      "bool": {
         "filter": [
            {
               "nested": {
                  "path": "features",
                  "query": {
                     "bool": {
                        "must_not": [
                           {
                              "exists": {
                                 "field": "features" // 或者"field": "features.comment"
                              }
                           }
                        ]
                     }
                  }
               }
            }
         ]
      }
   }
}

我们知道查询某个字段不存在，官方的文档：

curl -X GET "localhost:9200/_search?pretty" -H 'Content-Type: application/json' -d'
{
    "query": {
        "bool": {
            "must_not": {
                "exists": {
                    "field": "user"
                }
            }
        }
    }
}
'

所以我们也就会自然而然的在嵌套查询里把其加上类似的写法。

但是老外的评论里，给出的写法是：

If instead of putting the must_not inside your nested query, you put the nested query inside of a must_not, it should work:
中文是说：不是将must_not放到嵌套查询中里，而是将嵌套查询放到must_not中。

POST players/players/_search
{
  "query": {
    "bool": {
      "must_not": [
        {
          "nested": {
            "path": "features",
            "query": {
              "exists": {
                "field": "features"
              }
            }
          }
        }
      ]
    }
  }
}

把must_not放到嵌套查询中，会有个逻辑问题。嵌套查询是通过path来指定路径的。我们可以抽象的理解为：你已经进入了房间，却要在房间里判断这个房间是否存在。要判断房间是否存在应该在房间的外面才行。

MUST_NOT not working with EXIST in NESTED query