# Accuracy of date histogram sub-aggregation doc count under terms aggregation

**URL:** <https://discuss.elastic.co/t/accuracy-of-date-histogram-sub-aggregation-doc-count-under-terms-aggregation/348685>\
**Category:** Elasticsearch\
**Created:** [December 5, 2023, 10:26pm UTC](https://discuss.elastic.co/t/accuracy-of-date-histogram-sub-aggregation-doc-count-under-terms-aggregation/348685 "2023-12-05T22:26:57Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![myronmarston](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/myronmarston/32/73686_2.png) [@myronmarston](https://discuss.elastic.co/u/myronmarston)\
**Post date:** [December 5, 2023, 10:26pm UTC](https://discuss.elastic.co/t/accuracy-of-date-histogram-sub-aggregation-doc-count-under-terms-aggregation/348685/1 "2023-12-05T22:26:57Z")

</div>

Hello,

I am working on query that combines a terms aggregation with a date histogram sub-aggregation. I would like to get the doc count of each sub-aggregation bucket, determine if it is accurate, and, if it is not accurate, what the upper bound on the error is.

The [terms aggregation documentation](https://www.elastic.co/guide/en/elasticsearch/reference/8.11/search-aggregations-bucket-terms-aggregation.html#terms-agg-doc-count-error) mentions an accuracy issue to be aware of:

> Even with a larger `shard_size` value, `doc_count` values for a `terms` aggregation may be approximate. As a result, any sub-aggregations on the `terms` aggregation may also be approximate.

The `doc_count_error_upper_bound` field returned by a terms aggregation gives me the information I'm looking for. However, it is not returned on a date histogram aggregation (either as a stand-alone aggregation, or when used as a sub-aggregation).

For example, given this query:

```auto
GET /widgets_*/_search
{
  "aggs": {
    "term_groupings": {
      "terms": {
        "field": "options.color",
        "size": 5,
        "show_term_doc_count_error": true
      },
      "aggs": {
        "date_grouping": {
          "date_histogram": {
            "calendar_interval": "month",
            "min_doc_count": 1,
            "field": "created_at",
            "format": "strict_date_time"
          }
        }
      }
    }
  },
  "size": 0,
  "track_total_hits": false,
  "_source": false
}

```

...I get a response like this:

```auto
{
  "took": 13,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "max_score": null,
    "hits": []
  },
  "aggregations": {
    "term_groupings": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": "RED",
          "doc_count": 39,
          "doc_count_error_upper_bound": 0,
          "date_grouping": {
            "buckets": [
              {
                "key_as_string": "2023-10-01T00:00:00.000Z",
                "key": 1696118400000,
                "doc_count": 6
              },
              {
                "key_as_string": "2023-11-01T00:00:00.000Z",
                "key": 1698796800000,
                "doc_count": 33
              }
            ]
          }
        },
        {
          "key": "BLUE",
          "doc_count": 36,
          "doc_count_error_upper_bound": 0,
          "date_grouping": {
            "buckets": [
              {
                "key_as_string": "2023-10-01T00:00:00.000Z",
                "key": 1696118400000,
                "doc_count": 8
              },
              {
                "key_as_string": "2023-11-01T00:00:00.000Z",
                "key": 1698796800000,
                "doc_count": 28
              }
            ]
          }
        },
        {
          "key": "GREEN",
          "doc_count": 35,
          "doc_count_error_upper_bound": 0,
          "date_grouping": {
            "buckets": [
              {
                "key_as_string": "2023-10-01T00:00:00.000Z",
                "key": 1696118400000,
                "doc_count": 7
              },
              {
                "key_as_string": "2023-11-01T00:00:00.000Z",
                "key": 1698796800000,
                "doc_count": 28
              }
            ]
          }
        }
      ]
    }
  }
}

```

I get `doc_count_error_upper_bound` on the term grouping buckets, but not on the date  
histogram buckets. I understand that a date histogram aggregation does not suffer from  
the same accuracy issue that a terms aggregation does. However, as a sub-aggregation  
of a terms aggregation, could it suffer from that issue? (After all, the term aggregation  
documentation mentions that sub-aggregations can be affected). If so, how do I determine  
whether the date histogram bucket doc counts are accurate, and what the error upper bound  
might be?

Thanks!

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [January 2, 2024, 10:27pm UTC](https://discuss.elastic.co/t/accuracy-of-date-histogram-sub-aggregation-doc-count-under-terms-aggregation/348685/2 "2024-01-02T22:27:48Z")

</div>

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