如何使用 Elasticsearch 获取每个文档的平均缺失字段数？

Question

简而言之：使用 Elasticsearch，给定一个字段列表，我如何才能将每个文档的平均缺失字段数作为聚合？

详情

使用missing 聚合类型，我可以获得缺少给定字段的文档总数。所以有了以下数据：

"hits": [{
    "name": "A name",
    "nickname": "A nickname",
    "bestfriend": "A friend",
    "hobby": "An hobby"
},{
    "name": "A name",
    "hobby": "An hobby"
},{
    "name": "A name",
    "nickname": "A nickname",
    "hobby": "An hobby"
},{
    "name": "A name",
    "bestfriend": "A friend"
}]

我可以运行以下查询：

{
    "aggs": {
        "name_missing": {
            "missing": {"field": "name"}
        },
        "nickname_missing": {
            "missing": {"field": "nickname"}
        },
        "hobby_missing": {
            "missing": {"field": "hobby"}
        },
        "bestfriend_missing": {
            "missing": {"field": "bestfriend"}
        }
    }
}

我得到以下聚合：

...
"aggregations": {
    "name_missing": {
        "doc_count": 0
    },
    "nickname_missing": {
        "doc_count": 2
    },
    "hobby_missing": {
        "doc_count": 1
    },
    "bestfriend_missing": {
        "doc_count": 1
    }   
}
...

我现在需要的是获取每个文档的缺失字段的平均数。我可以通过代码对结果进行数学运算：

• 总结所有missing聚合doc_count值
• 除以总点击次数

但是，如何从 Elasticsearch 中获得与聚合相同的结果？

感谢您的任何回复/建议。

Answer 1

这是一个丑陋的解决方案，但可以解决问题。

GET missing/missing/_search
{
  "size": 0,
  "aggs": {
    "result": {
      "terms": {
        "script": "'aaa'"
      },
      "aggs": {
        "name_missing": {
          "missing": {
            "field": "name"
          }
        },
        "nickname_missing": {
          "missing": {
            "field": "nickname"
          }
        },
        "hobby_missing": {
          "missing": {
            "field": "hobby"
          }
        },
        "bestfriend_missing": {
          "missing": {
            "field": "bestfriend"
          }
        },
        "avg_missing": {
          "bucket_script": {
            "buckets_path": {            // This is kind of defining variables. name_missing._count will take the doc_count of the name_missing aggregation and same for others(nickname_missing,hobby_missing,bestfriend_missing) as well. "count":"_count" will take doc_count of the documents on which aggregation is performed(total no. of Hits).
              "name_missing": "name_missing._count",
              "nickname_missing": "nickname_missing._count",
              "hobby_missing": "hobby_missing._count",
              "bestfriend_missing": "bestfriend_missing._count",
              "count":"_count"
            },
            "script": "(name_missing+nickname_missing+hobby_missing+bestfriend_missing)/count" // Here we are adding all the missing values and dividing it by the total no. of Hits as you require.
          }
        }
      }
    }
  }
}

我已经向你展示了如何做到这一点，现在由你来决定如何调整你的参数并提取你想要的。