title: elasticsearch composite aggs with nested object
body: <p>I have an object with nested field.</p>
  
  <pre><code>  "parameters": {
          "type": "nested",
          "properties": {
            "id": {
              "type": "integer"
            },
            "values": {
              "type": "keyword"
            }
          }
        }
  </code></pre>
  
  <p>I am trying aggregate operation:</p>
  
  <pre><code>GET places/place/_search?size=0
  {
    "query": {
      "match_all": {}
    },
    "aggs": {
      "parameters": {
        "nested": {
          "path": "parameters"
        },
        "aggs": {
          "parameters_cnt_i": {
            "terms": {
              "field": "parameters.id",
              "size": 100
            },
            "aggs": {
              "parameters_cnt_v": {
                "terms": {
                  "field": "parameters.values",
                  "size": 100
                }
              }
            }
          }
        }
      }
    }
  }
  </code></pre>
  
  <p>but it is not good, because  i set a "size" too large. 
  in docs says </p>
  
  <p><strong>If you want to retrieve all terms or all combinations of terms in a nested terms aggregation you should use the Composite aggregation</strong></p>
  
  <p>but i cant understand how to use a Composite aggregation with nested object.. its real?</p>