子关联聚合 #

children 子关联聚合是一种存储分组聚合，它根据索引中定义的父子关系创建包含子文档的单个存储分组。

子关联聚合与 join 字段类型配合使用，以聚合与父文档关联的子文档。

子关联聚合标识与特定子关系名称匹配的子文档，而 parent 父聚合标识具有匹配子文档的父文档。这两个聚合都采用子关系名称作为输入。

参数说明 #

children 聚合采用以下参数。

参考样例 #

以下示例构建一个包含三名员工的小型公司数据库。每个员工记录都与父部门记录具有子联接关系。

首先，创建一个 company 索引，其中包含一个将部门（父级）映射到员工（子级）的联接字段：

PUT /company
{
  "mappings": {
    "properties": {
      "join_field": {
        "type": "join",
        "relations": {
          "department": "employee"
        }
      },
      "department_name": {
        "type": "keyword"
      },
      "employee_name": {
        "type": "keyword"
      },
      "salary": {
        "type": "double"
      },
      "hire_date": {
        "type": "date"
      }
    }
  }
}

接下来，使用三个部门和三名员工填充数据。下表显示了父子分配。

routing 参数可确保父文档和子文档存储在同一分片上，这是父子关系在 Easysearch 中正常运行所必需的：

POST _bulk?routing=1
{ "create": { "_index": "company", "_id": "1" } }
{ "type": "department", "department_name": "Accounting", "join_field": "department" }
{ "create": { "_index": "company", "_id": "2" } }
{ "type": "department", "department_name": "Engineering", "join_field": "department" }
{ "create": { "_index": "company", "_id": "3" } }
{ "type": "department", "department_name": "HR", "join_field": "department" }
{ "create": { "_index": "company", "_id": "4" } }
{ "type": "employee", "employee_name": "Abel Anderson", "salary": 120000, "hire_date": "2024-04-04", "join_field": { "name": "employee",  "parent": "1" } }
{ "create": { "_index": "company", "_id": "5" } }
{ "type": "employee", "employee_name": "Betty Billings", "salary": 140000, "hire_date": "2023-05-05", "join_field": { "name": "employee",  "parent": "1" } }
{ "create": { "_index": "company", "_id": "6" } }
{ "type": "employee", "employee_name": "Carl Carter", "salary": 140000, "hire_date": "2020-06-06",  "join_field": { "name": "employee",  "parent": "2" } }

以下请求查询所有部门，然后筛选名为 Accounting 的部门。然后，它使用子关联聚合来选择与会计部门具有子关系的两个单据。最后，avg 子关联聚合返回会计员工工资的平均值：

GET /company/_search
{
  "size": 0,
  "query": {
    "bool": {
      "filter": [
        {
          "term": {
            "join_field": "department"
          }
        },
        {
          "term": {
            "department_name": "Accounting"
          }
        }
      ]
    }
  },
  "aggs": {
    "acc_employees": {
      "children": {
        "type": "employee"
      },
      "aggs": {
        "avg_salary": {
          "avg": {
            "field": "salary"
          }
        }
      }
    }
  }
}

返回内容包含所选部门存储分组，查找部门的员工类型子级，并计算其工资的平均值 ：

{
  "took": 379,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 1,
      "relation": "eq"
    },
    "max_score": null,
    "hits": []
  },
  "aggregations": {
    "acc_employees": {
      "doc_count": 2,
      "avg_salary": {
        "value": 110000
      }
    }
  }
}