Nested Aggregation

A special single bucket aggregation that enables aggregating nested documents.

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

{
    ...

    "product" : {
        "properties" : {
            "resellers" : { 
                "type" : "nested",
                "properties" : {
                    "name" : { "type" : "string" },
                    "price" : { "type" : "double" }
                }
            }
        }
    }
}

The resellers is an array that holds nested documents under the product object.

The following aggregations will return the minimum price products can be purchased in:

{
    "query" : {
        "match" : { "name" : "led tv" }
    },
    "aggs" : {
        "resellers" : {
            "nested" : {
                "path" : "resellers"
            },
            "aggs" : {
                "min_price" : { "min" : { "field" : "resellers.price" } }
            }
        }
    }
}

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:

{
    "aggregations": {
        "resellers": {
            "min_price": {
                "value" : 350
            }
        }
    }
}