即使没有数据，在固定日期范围内(即固定数量的存储桶)的直方图 [英] Histogram over fixed range of dates (i.e. fixed number of buckets) even when data is absent

问题描述

我的目标是在开始日期和结束日期之间建立直方图，空日期应显示在直方图中，并且计数值为零.

My goal is to build a histogram between a start and an end dates, the empty dates should appear in the histogram and have zero as a count value.

我正在尝试以下查询以获取最近7天:

I am trying the following query to fetch the last 7 days:

POST my_index/_search
{
  "size": 0,
  "query": {
    "range": {
      "date": {
        "gte": "now-7d/d",
        "lte": "now/d"
        }
      }
  },
  "aggs" : {
      "count_per_day" : {
          "date_histogram" : {
              "field" : "date",
              "interval" : "day",
              "order": {"_key": "desc"},
              "min_doc_count": 0
          }
      }
  }
}

问题在于我只有最近3天的数据，因此3天之前没有任何数据.在这种情况下，结果仅包含最近3天，而前几天完全不返回.

The issues is that I have data only for the last 3 days, so there is no data at all prior to 3 days ago. In this case, the result contains only the last 3 days and the previous days are not returned at all.

但是，如果存在差距(即6天前有数据，但第5天和第4天没有数据)，则空天将以零作为计数出现.

But if there is a gap (i.e. there is data 6 days ago, but no data in the 5th and the 4th day), the empty days will appear with zero as a count.

即使没有数据，如何强制返回缺席日期?换句话说，即使没有数据，如何确定存储桶的数量(在上面的示例中为7)?

How can I force to return the absent dates even if there is no data? In other word, how to fix the number of buckets (to 7 in the example above) even if there is no data?

推荐答案

您已经添加了"min_doc_count":0 以包含空存储桶.您需要做的就是简单地添加 extended_bounds 参数以及强制开始和结束存储桶.可以在

You have already added "min_doc_count": 0 to include empty buckets. All you need to do is to simply add extended_bounds param as well to force starting and ending buckets. More on it can be found here.

如下更新查询:

{
  "size": 0,
  "query": {
    "range": {
      "date": {
        "gte": "now-7d/d",
        "lte": "now/d"
      }
    }
  },
  "aggs": {
    "count_per_day": {
      "date_histogram": {
        "field": "date",
        "interval": "day",
        "order": {
          "_key": "desc"
        },
        "min_doc_count": 0,
        "extended_bounds": {
          "min": "now-7d/d",
          "max": "now/d"
        }
      }
    }
  }
}

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