# Aggs returning more Cardinality than Source documents
**URL:** https://discuss.elastic.co/t/aggs-returning-more-cardinality-than-source-documents/268142
**Category:** Elasticsearch
**Created:** [March 23, 2021, 9:44pm UTC](https://discuss.elastic.co/t/aggs-returning-more-cardinality-than-source-documents/268142 "2021-03-23T21:44:20Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@LeeBear](https://discuss.elastic.co/u/LeeBear)
#### Post date: [March 23, 2021, 9:44pm UTC](https://discuss.elastic.co/t/aggs-returning-more-cardinality-than-source-documents/268142/1 "2021-03-23T21:44:20Z")
I am running:
```auto
{
"size": 0,
"track_total_hits": true,
"query": {
"bool": {
"must": [
{"match": {"prgx_email_join": {"query": "attachmentChild" } } }
]
}
},
"aggs": {
"attachment_count" : {
"cardinality": {
"script": {
"source": "doc['_id'].value.substring(48)"
}
}
}
}
}
```
And the results are:
```auto
{
"took": 20433,
"timed_out": false,
"_shards": {
"total": 6,
"successful": 6,
"skipped": 0,
"failed": 0
},
"hits": {
"total": {
"value": 34924205,
"relation": "eq"
},
"max_score": null,
"hits": []
},
"aggregations": {
"attachment_count": {
"value": 35113251
}
}
}
```
How does the **attachment\_count** exceed the **hits.total.value**?
---
### Author:  [@Mark\_Harwood](https://discuss.elastic.co/u/Mark_Harwood)
#### Post date: [March 23, 2021, 10:39pm UTC](https://discuss.elastic.co/t/aggs-returning-more-cardinality-than-source-documents/268142/2 "2021-03-23T22:39:48Z")
Hi Lee,
From [the docs](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-cardinality-aggregation.html):
> A `single-value` metrics aggregation that calculates an approximate count of distinct values.
The key word here is approximate - exact counts are not possible at scale with speed.
---
### Author:  [@LeeBear](https://discuss.elastic.co/u/LeeBear)
#### Post date: [March 24, 2021, 6:22pm UTC](https://discuss.elastic.co/t/aggs-returning-more-cardinality-than-source-documents/268142/3 "2021-03-24T18:22:23Z")
Good to know, I would think that even an approximation would use the upper limit of the match.
---
### Author:  [@Mark\_Harwood](https://discuss.elastic.co/u/Mark_Harwood)
#### Post date: [March 25, 2021, 6:57pm UTC](https://discuss.elastic.co/t/aggs-returning-more-cardinality-than-source-documents/268142/4 "2021-03-25T18:57:08Z")
> [@LeeBear](#):
>
> , I would think that even an approximation would use the upper limit of the match
When you have multi-value fields (or scripts that can generate multiple values) there is no upper limit
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [April 22, 2021, 6:57pm UTC](https://discuss.elastic.co/t/aggs-returning-more-cardinality-than-source-documents/268142/5 "2021-04-22T18:57:19Z")
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