Elasticsearch distinct count on nested fields

Question

According to docs, distinct count can be achieved approximately by using cardinality. https://www.elastic.co/guide/en/elasticsearch/guide/current/cardinality.html

I have a large store of data of type like this:

{
    {
        "foo": {
            "bar": "a1"
        }
    },
    {
        "foo": {
            "bar": "a2"
        }
    }
}

and I want to do a distinct count of "foo.bar" values.

My DSL query:

{
    "size": 0,
    "aggs": {
        "number_of_bars": {
            "cardinality": {
                "field": "bar"
            }
        }
    }
}

returns "number_of_bars": 0. I was also trying "field": "foo.bar", which results in an error.

Can you tell me, what I am doing wrong?

What was the error ? Cause with field foo.bar it works fine for me. Can you also post the relevant part of the mapping please ? Thx — Pierre Mallet
– Pierre Mallet, Commented Jul 4, 2018 at 13:04
The error was: "Fielddata is disabled on text fields by default. Set fielddata=true on [foo.bar] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead." I don't know what is meant by "relevant part of mapping", sorry I'm new to elasticsearch. — Libor
– Libor, Commented Jul 4, 2018 at 13:40

TechnocratSid · Accepted Answer · 2018-07-04 14:06:31Z

2

Use this:

{
    "size": 0,
    "aggs": {
        "number_of_bars": {
            "cardinality": {
                "field": "foo.bar.keyword"
            }
        }
    }
}

answered Jul 4, 2018 at 14:06

TechnocratSid

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