Aggregate over top hits ElasticSearch

Question

My documents are structured in the following way:

{
   "chefInfo": {
      "id": int,
      "employed": String
      ... Some more recipe information ...
   }
   "recipe": {
      ... Some recipe information ...
   }
}

If a chef has multiple recipes, the nested chefInfo block will be identical in each document. My problem is that I want to do an aggregation of a field in the chefInfo part of the document. However, this doesn't take into account for the fact that the chefInfo block is a duplicate.

So, if the chef with the id of 1 is on 5 recipes and I am aggregating on the employed field then this particular chef, will represent 5 of the counts in the aggregation, whereas, I want them to only count a single one.

I thought about doing a top_hits aggregation on the chef_id and then I wanted to do a sub-aggregation over all of the buckets but I can't work out how to do the counts over the results of all the buckets.

Is it possible what I want to do?

Answer 1

For elastic every document in itself is unique. In your case you want to define uniqueness based on a different field, here chefInfo.id. To find unique count based on this field you have to make use of cardinality aggregation.

You can apply the aggregation as below:

{
  "aggs": {
    "employed": {
      "nested": {
        "path": "chefInfo"
      },
      "aggs": {
        "employed": {
          "terms": {
            "field": "chefInfo.employed.keyword"
          },
          "aggs": {
            "employed_unique": {
              "cardinality": {
                "field": "chefInfo.id"
              }
            }
          }
        }
      }
    }
  }
}

In the result employed_unique give you the expected count.