Counting histogram buckets

count_buckets.http

POST metricbeat/_search
{
  "size": 0,
  "aggs": {
    "date_histo": {
      "date_histogram": {
        "field": "@timestamp",
        "interval": "day"
      }
    },
    "date_histo_stats": {
      "stats_bucket": {
        "buckets_path": "date_histo._count"
      }
    }
  }
}

{
  "took": 251,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 15918724,
    "max_score": 0,
    "hits": []
  },
  "aggregations": {
    "date_histo": {
      "buckets": [
        {
          "key_as_string": "2018-05-02T00:00:00.000Z",
          "key": 1525219200000,
          "doc_count": 435323
        },
        {
          "key_as_string": "2018-05-03T00:00:00.000Z",
          "key": 1525305600000,
          "doc_count": 2792306
        },
        {
          "key_as_string": "2018-05-04T00:00:00.000Z",
          "key": 1525392000000,
          "doc_count": 2729772
        },
        {
          "key_as_string": "2018-05-05T00:00:00.000Z",
          "key": 1525478400000,
          "doc_count": 2721635
        },
        {
          "key_as_string": "2018-05-06T00:00:00.000Z",
          "key": 1525564800000,
          "doc_count": 2721417
        },
        {
          "key_as_string": "2018-05-07T00:00:00.000Z",
          "key": 1525651200000,
          "doc_count": 2725446
        },
        {
          "key_as_string": "2018-05-08T00:00:00.000Z",
          "key": 1525737600000,
          "doc_count": 1792825
        }
      ]
    },
    "date_histo_stats": {
      "count": 7,
      "min": 435323,
      "max": 2792306,
      "avg": 2274103.4285714286,
      "sum": 15918724
    }
  }
}