es - elasticsearch - aggs - bucket - children

世界上并没有完美的程序，但是我们并不因此而沮丧，因为写程序就是一个不断追求完美的过程。

问：children有什么特点？
答：

问：children如何使用？
答：

# 删除
DELETE /children_test

# 映射
PUT /children_test
{
  "mappings": {
    "properties": {
      "join": {
        "type": "join",
        "relations": {
          "question": "answer"
        }
      },
      "q": {"type": "keyword"},
      "a": {"type": "keyword"}
    }
  }
}

# 索引
POST /children_test/_bulk?routing=1&refresh
{"index": {"_id": 1}}
{"join": {"name": "question"},"q": "is this my question?"}
{"index": {"_id": 2}}
{"join": {"name": "answer","parent": 1},"a": "yes answer one"}
{"index": {"_id": 3}}
{"join": {"name": "answer","parent": 1},"a": "yes answer two"}
{"index": {"_id": 4}}
{"join": {"name": "answer","parent": 1},"a": "yes answer three"}


# 搜索
GET /children_test/_search
{
  "size": 0,
  "aggs": {
    "qa_aggs": {
      "terms": {
        "field": "q",
        "size": 10
      },
      "aggs": {
        "a_aggs": {
          "children": {
            "type": "answer"
          },
          "aggs": {
            "a_content": {
              "terms": {
                "field": "a",
                "size": 10
              }
            }
          }
        }
      }
    }
  }
}

# 结果
{
  "took" : 2,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 4,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "qa_aggs" : {
      "doc_count_error_upper_bound" : 0,
      "sum_other_doc_count" : 0,
      "buckets" : [
        {
          "key" : "is this my question?",
          "doc_count" : 1,
          "a_aggs" : {
            "doc_count" : 3,
            "a_content" : {
              "doc_count_error_upper_bound" : 0,
              "sum_other_doc_count" : 0,
              "buckets" : [
                {
                  "key" : "yes answer one",
                  "doc_count" : 1
                },
                {
                  "key" : "yes answer three",
                  "doc_count" : 1
                },
                {
                  "key" : "yes answer two",
                  "doc_count" : 1
                }
              ]
            }
          }
        }
      ]
    }
  }
}