Get related metric in INTERSECT queries... or have an aggregation based on PostAggregation

I am trying to find out a metric column for those users that are in the intersection of two sets.

For example in the below groupBy intersect example, is it possible to get a metric only in the post aggregation stage?

The below example is from http://druid.io/docs/latest/development/extensions-core/datasketches-aggregators

{
  "queryType": "groupBy",
  "dataSource": "test_datasource",
  "granularity": "ALL",
  "dimensions": [],
  "filter": {
    "type": "or",
    "fields": [
      {"type": "selector", "dimension": "product", "value": "A"},
      {"type": "selector", "dimension": "product", "value": "B"}
    ]
  },
  "aggregations": [
    {
      "type" : "filtered",
      "filter" : {
        "type" : "selector",
        "dimension" : "product",
        "value" : "A"
      },
      "aggregator" :     {
        "type": "thetaSketch", "name": "A_unique_users", "fieldName": "user_id_sketch"
      }
    },
    {
      "type" : "filtered",
      "filter" : {
        "type" : "selector",
        "dimension" : "product",
        "value" : "B"
      },
      "aggregator" :     {
        "type": "thetaSketch", "name": "B_unique_users", "fieldName": "user_id_sketch"
      }
    }
  ],
  "postAggregations": [
    {
      "type": "thetaSketchEstimate",
      "name": "final_unique_users",
      "field":
      {
        "type": "thetaSketchSetOp",
        "name": "final_unique_users_sketch",
        "func": "INTERSECT",
        "fields": [
          {
            "type": "fieldAccess",
            "fieldName": "A_unique_users"
          },
          {
            "type": "fieldAccess",
            "fieldName": "B_unique_users"
          }
        ]
      }
    }
  ],
  "intervals": [
    "2014-10-19T00:00:00.000Z/2014-10-22T00:00:00.000Z"
  ]
}

``

What i need in the postAggregations is a field like “number_of_products” … which tells me for all the users using both product A and product B, what is the number of products of each type A and B.

Something like below:

  **{** ** "type" : "longSum", "name" : "number_of_products", "fieldName" : "num_products" }**
"postAggregations": [
    {
      "type": "thetaSketchEstimate",
      "name": "final_unique_users",
      "field":
      {
        "type": "thetaSketchSetOp",
        "name": "final_unique_users_sketch",
        "func": "INTERSECT",
        "fields": [
          {
            "type": "fieldAccess",
            "fieldName": "A_unique_users"
          },
          {
            "type": "fieldAccess",
            "fieldName": "B_unique_users"
          }
        ]
      }
    },

  ]

``