概述

继续跟中华石杉老师学习ES，第46篇

课程地址： https://www.roncoo.com/view/55

官方说明

Cardinality Aggregation：戳这里

es中的去重，cartinality metric，对每个bucket中的指定的field进行去重，取去重后的count，类似于count(distcint)

示例

GET /tvs/sales/_search
{
  "aggs": {
    "month":{
      "date_histogram": {
        "field": "sold_date",
        "interval": "month"
      },
      "aggs": {
        "distinct_brand_cnt": {
          "cardinality": {
            "field": "brand"
          }
        }
      }
    }
  },
  "size": 0
}

返回：

{
  "took": 8,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 8,
    "max_score": 0,
    "hits": []
  },
  "aggregations": {
    "month": {
      "buckets": [
        {
          "key_as_string": "2016-05-01T00:00:00.000Z",
          "key": 1462060800000,
          "doc_count": 1,
          "distinct_brand_cnt": {
            "value": 1
          }
        },
        {
          "key_as_string": "2016-06-01T00:00:00.000Z",
          "key": 1464739200000,
          "doc_count": 0,
          "distinct_brand_cnt": {
            "value": 0
          }
        },
        {
          "key_as_string": "2016-07-01T00:00:00.000Z",
          "key": 1467331200000,
          "doc_count": 1,
          "distinct_brand_cnt": {
            "value": 1
          }
        },
        {
          "key_as_string": "2016-08-01T00:00:00.000Z",
          "key": 1470009600000,
          "doc_count": 1,
          "distinct_brand_cnt": {
            "value": 1
          }
        },
        {
          "key_as_string": "2016-09-01T00:00:00.000Z",
          "key": 1472688000000,
          "doc_count": 0,
          "distinct_brand_cnt": {
            "value": 0
          }
        },
        {
          "key_as_string": "2016-10-01T00:00:00.000Z",
          "key": 1475280000000,
          "doc_count": 1,
          "distinct_brand_cnt": {
            "value": 1
          }
        },
        {
          "key_as_string": "2016-11-01T00:00:00.000Z",
          "key": 1477958400000,
          "doc_count": 2,
          "distinct_brand_cnt": {
            "value": 1
          }
        },
        {
          "key_as_string": "2016-12-01T00:00:00.000Z",
          "key": 1480550400000,
          "doc_count": 0,
          "distinct_brand_cnt": {
            "value": 0
          }
        },
        {
          "key_as_string": "2017-01-01T00:00:00.000Z",
          "key": 1483228800000,
          "doc_count": 1,
          "distinct_brand_cnt": {
            "value": 1
          }
        },
        {
          "key_as_string": "2017-02-01T00:00:00.000Z",
          "key": 1485907200000,
          "doc_count": 1,
          "distinct_brand_cnt": {
            "value": 1
          }
        }
      ]
    }
  }
}

我们来看下原始数据：

来看下我们的统计结果，找个 2016-11

统计正确。