{
  "columns": [
    "sum(invoiceAmount) as amount",
    "count(invoiceId) as billCount",
    "count_distinct(customerId) as buyers"
  ],
  "slice": [
    {
      "field": "invoiceDate",
      "op": "[)",
      "value": [
        "2012-01-01",
        "2013-01-01"
      ]
    }
  ],
  "limit": 2
}