elasticsearch参数copy_to，elasticsearch

elasticsearch参数copy_to，elasticsearch

非嵌套同级聚合多个字段

在使用elasticsearch时遇见了这样的需求：es聚合指定字段时聚合的结果里面只显示聚合的字段。但是在做报表时，我们发现一个问题：如果我们对员工进行聚合，但是我们还希望查看当前员工所在的班组，部门等信息。这时如果查询es两次，对于效率来说是不好的。所以我们在这里使用一个es的字段特性：copy_to

使用的步骤：

1、创建mapping

PUT my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "first_name": {
          "type": "keyword",
          "copy_to": "full_name"
        },
        "last_name": {
          "type": "keyword",
          "copy_to": "full_name"
        },
        "full_name": {
          "type": "text",
          "fielddata": true
        }
      }
    }
  }
}

2、插入数据

PUT my_index/my_type/1
{
  "first_name": "John",
  "last_name": "Smith"
}

3、查询校验

GET my_index/_search
{
  "query": {
    "match": {
      "full_name": { 
        "query": "John Smith",
        "operator": "and"
      }
    }
  }
}

4、结果展示

{
  "took": 0,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 1,
    "max_score": 0.51623213,
    "hits": [
      {
        "_index": "my_index",
        "_type": "my_type",
        "_id": "1",
        "_score": 0.51623213,
        "_source": {
          "first_name": "John",
          "last_name": "Smith"
        }
      }
    ]
  }
}

5、聚合查询校验

{
  "query": {
    
  },"aggs": {
    "1": {
      "terms": {
        "field": "full_name",
        "size": 10
      }
    }
  }
}

6、查询结果

{
  "took": 0,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 1,
    "max_score": 1,
    "hits": [
      {
        "_index": "baobiaoceshi4",
        "_type": "my_type",
        "_id": "1",
        "_score": 1,
        "_source": {
          "first_name": "John",
          "last_name": "Smith"
        }
      }
    ]
  },
  "aggregations": {
    "1": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": "john",
          "doc_count": 1
        },
        {
          "key": "smith",
          "doc_count": 1
        }
      ]
    }
  }
}

注意有这几个问题：

1、我们copy_to指向的字段字段类型要为：text

2、text类型字段如果希望进行聚合，设置属性:"fielddata": true

3、copy_to指向的字段不会在head插件查看时显示，但是能通过查询语句作为条件
总结：通过这种方式对我们的结果进行聚合，能够满足一次查询聚合多个字段。非常棒！

官网文档地址：https://www.elastic.co/guide/en/elasticsearch/reference/current/copy-to.html