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父级聚合

parent 聚合是一个桶聚合，它根据索引中定义的父子关系创建一个包含父文档的单个桶。此聚合使您能够对具有相同匹配子文档的父文档执行分析，从而实现强大的层次化数据分析。

parent 聚合与 join 字段类型一起使用，该字段类型在同一索引中的文档内建立父子关系。

parent 聚合识别具有匹配子文档的父文档，而 children 聚合识别匹配特定子关系的子文档。这两种聚合都将子关系名称作为输入。

参数

parent 聚合接受以下参数：

参数 必需/可选 数据类型 描述
type 必需 字符串 来自 join 字段的子类型名称。

示例

以下示例构建了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 join 关系。

首先，创建一个包含 join 字段的 company 索引，该字段将部门（父级）映射到员工（子级）：

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。父子分配如下表所示。

部门（父级） 员工（子级）
会计 Abel Anderson、Betty Billings
工程 Carl Carter
人力资源部 无

routing 参数确保父文档和子文档存储在同一个分片上，这是 OpenSearch 中父子关系正常工作的必要条件。

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" } }

最后，运行所有与一名或多名员工具有父子关系的部门的聚合。

GET /company/_search
{
  "size": 0,
  "aggs": {
    "all_departments": {
      "parent": {
        "type": "employee"
      },
      "aggs": {
        "departments": {
          "terms": {
            "field": "department_name"
          }
        }
      }
    }
  }
}

示例响应

all_departments 父聚合返回所有包含员工子文档的部门。请注意，人力资源部门未在其中显示。

{
  "took": 3,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 6,
      "relation": "eq"
    },
    "max_score": null,
    "hits": []
  },
  "aggregations": {
    "all_departments": {
      "doc_count": 2,
      "departments": {
        "doc_count_error_upper_bound": 0,
        "sum_other_doc_count": 0,
        "buckets": [
          {
            "key": "Accounting",
            "doc_count": 1
          },
          {
            "key": "Engineering",
            "doc_count": 1
          }
        ]
      }
    }
  }
}
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