elasticsearch - Aggregation on top N results

Question

Problem:

If I search for "iphone" I get 400 product results and the product category aggregation I have returns the top 3 categories in the results set.

Those categories would include smartphones, phone cases and mobile phone accessories.

If I search "iphone 6" I get 1400 results because of the extra "6" returns matches to more products. The product category aggregation now returns the top 3 categories for all those results.

The top 3 product categories will now be everything from cables to computer monitors.

What I need to do is get the top 3 categories for the top 100 results.

---

What I've tried:

I've tried using the top_hits aggregation within the top category aggregation but that only returns the top products in each category.

Something like this:

{
    "aggs": {

        "product_categories": {
            "terms": {
                "field": "product_category",
                "size": 10,
            }
        }        
        "aggs": {
            "top-categories": {
                "top_hits": {
                    "size" : 3
                }
            }
        }
    }
}

---

I've also tried creating a top_hits aggregation with a sub-aggregation within to get the top categories but that doesn't work either.

{
    "aggs": {
        "top-categories": {
            "top_hits": {
                "size" : 100
            }
            "aggs": {
                "product_categories": {
                    "terms": {
                        "field": "product_category",
                        "size": 3,
                    }
                }
            }
        }
    }
}

---

Can anyone help me with this problem?

Answer 1

You could try using a filter aggregation based on a limit filter, and nest your terms aggregation in it.

Be aware that the limit is applied at shard level (see the documentation).

However, this should do the job for your case, with a query like :

{
  "aggs": {
    "limit_results": {
      "filter": {
        "limit": {
          "value": 100
        }
      },
      "aggs": {
        "product_categories": {
          "terms": {
            "field": "product_category",
            "size": 10
          }
        }
      }
    }
  }
}