Elasticsearch count in groups by date range

Question

I have documents like this:

{
body: 'some text',
read_date: '2017-12-22T10:19:40.223000'
}

Is there a way to query count of documents published in last 10 days group by date? For example:

2017-12-22, 150  
2017-12-21, 79  
2017-12-20, 111  
2017-12-19, 27  
2017-12-18, 100  

Answer 1

Yes, you can easily achieve that using a date_histogram aggregation, like this:

{
  "query": {
    "range": {
      "read_date": {
        "gte": "now-10d"
      }
    }
  },
  "aggs": {
    "byday": {
      "date_histogram": {
        "field": "read_date",
        "interval": "day"
      }
    }
  }
}

Answer 2

To receive day count of the past 10 days, per day you can POST the following query:

{
  "query": {
    "range": {
      "read_date": {
        "gte": "now-11d/d",
        "lte": "now-1d/d"
      }
    }
  },

    "aggs" : {
        "byDay" : {
            "date_histogram" : {
                "field" : "read_date",
                "calendar_interval" : "1d",
                "format" : "yyyy-MM-dd" 
            }
        }
    }
}

To the following Url: http://localhost:9200/Index_Name/Index_Type/_search?size=0

Setting size to 0 avoids executing the fetch phase of the search making the request more efficient. See this elastic documentation for more information.