Elatsicsearch聚合了MongoDB $ unwind步骤的等价

Question

这个问题非常简单，在Elasticserch聚合中是否有相当于来自MongoDB聚合框架的$ unwind操作？

Answer 1

要注意的重要一点是，与展开相比，ElasticSearch聚合不会重建这些文档，而是将聚合结果划分为存储桶。其余的解析工作将强加给客户。

示例，此查询：

{
  "size": 0,
  "aggregations": {
    "array_aggregation": {
      "terms": {
        "field": "array_items",
        "size": 10
      },
      "aggregations": {
        "other_field_aggregation": {
          "terms": {
            "field": "some_other_field",
            "size": 10
          }
        }
      }
    }
  }
}

结果：

{
  "took": 59,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "failed": 0
  },
  "hits": {
    "total": 163,
    "max_score": 0,
    "hits": []
  },
  "aggregations": {
    "array_aggregation": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": "itemA",
          "doc_count": 3858,
          "other_field_aggregation": {
            "doc_count_error_upper_bound": 0,
            "sum_other_doc_count": 0,
            "buckets": [
              {
                "key": "fieldA",
                "doc_count": 3858
              },
              {
                "key": "fieldB",
                "doc_count": 4050
              }
            ]
          }
        },
        {
          "key": "itemB",
          "doc_count": 3858,
          "other_field_aggregation": {
            "doc_count_error_upper_bound": 0,
            "sum_other_doc_count": 0,
            "buckets": [
              {
                "key": "fieldA",
                "doc_count": 3858
              },
              .
              .
              .
            ]
          }
        },
        .
        .
        .
      ]
    }
  }
}

这不是最好的解决方案，但可以成为一个好的起点。