Cardinality aggregation query calculates an approximate count of distinct values. How we can calculate the cardinality distribution of documents?
For example suppose we have:
a,a,a,b,b,b,c,c,d,d,e
and distinct count distribution is:
3: 2 # count of distint element that have 3 occurnes (a, b)
2: 2 # c, d
1: 1 # e
Actually you cannot do aggregations like this.
But, using transform API (https://www.elastic.co/guide/en/elasticsearch/reference/current/transform-examples.html) you could create a new index to do a simple terms aggregation:
PUT _transform/so
{
"dest" : {
"index" : "my-so"
},
"source": {
"index": "my-index"
},
"pivot": {
"group_by": {
"country": {
"terms": {
"field": "letter"
}
}
},
"aggregations": {
"cardinality": {
"value_count": {
"field" : "letter"
}
}
}
}
}
This will give you:
[
{
"country" : "a",
"cardinality" : 22
},
{
"country" : "b",
"cardinality" : 4
},
{
"country" : "c",
"cardinality" : 5049
}...
Then, you can use simple terms or histogram aggregation:
GET /my-so/_search
{
"size" : 0,
"aggs": {
"cc": {
"terms": {
"field": "cardinality"
}
}
}
}
