Elasticsearch返回聚合后的详情，类似MySQL的group_concat

es聚合后，默认返回结构并不会显示参加聚合的文档的详情，在此记录可实现的两种方法

方法一：top_hits

GET items/_search?size=0
{
  "aggs": {
    "art_no_repeat": {
      "terms": {
        "field": "art_no",
        "min_doc_count": 2,
        "size": 20
      },
      "aggs": {
        "top_art_no": {
          "top_hits": {
            "size": 10
          }
        }
      }
    }
  }
}

方法二：collapse+inner_hits

GET items/_search?size=3
{
  "query": {
    "match": {
      "art_no.keyword": "九尾狐鞋业&A01"
    }
  },
  "collapse": {
    "field": "art_no",
    "inner_hits": {
      "name": "top_item",
      "size": 2
    }
  }
}