OpenSearch/docs/reference/aggregations/bucket/nested-aggregation.asciidoc

[[search-aggregations-bucket-nested-aggregation]]
=== Nested Aggregation

A special single bucket aggregation that enables aggregating nested documents.

For example, lets say we have an index of products, and each product holds the list of resellers - each having its own
price for the product. The mapping could look like:

[source,console]
--------------------------------------------------
PUT /products
{
  "mappings": {
    "properties": {
      "resellers": { <1>
        "type": "nested",
        "properties": {
          "reseller": { "type": "text" },
          "price": { "type": "double" }
        }
      }
    }
  }
}
--------------------------------------------------
<1> `resellers` is an array that holds nested documents.

The following request adds a product with two resellers:

[source,console]
--------------------------------------------------
PUT /products/_doc/0
{
  "name": "LED TV", <1>
  "resellers": [
    {
      "reseller": "companyA",
      "price": 350
    },
    {
      "reseller": "companyB",
      "price": 500
    }
  ]
}
--------------------------------------------------
// TEST[s/PUT \/products\/_doc\/0/PUT \/products\/_doc\/0\?refresh/]
// TEST[continued]
<1> We are using a dynamic mapping for the `name` attribute.


The following request returns the minimum price a product can be purchased for:

[source,console]
--------------------------------------------------
GET /products/_search
{
  "query": {
    "match": { "name": "led tv" }
  },
  "aggs": {
    "resellers": {
      "nested": {
        "path": "resellers"
      },
      "aggs": {
        "min_price": { "min": { "field": "resellers.price" } }
      }
    }
  }
}
--------------------------------------------------
// TEST[s/GET \/products\/_search/GET \/products\/_search\?filter_path=aggregations/]
// TEST[continued]

As you can see above, the nested aggregation requires the `path` of the nested documents within the top level documents.
Then one can define any type of aggregation over these nested documents.

Response:

[source,console-result]
--------------------------------------------------
{
  ...
  "aggregations": {
    "resellers": {
      "doc_count": 2,
      "min_price": {
        "value": 350
      }
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[s/\.\.\.//]
// TESTRESPONSE[s/: [0-9]+/: $body.$_path/]