When does node-mysql return `fields` as part of a query result

Question

According to the node-mysql documentation, the callback to a query will get three parameters - an error, the row(s) or result of the query, and something called fields which may or may not be passed everytime.

fields will contain information about the returned results fields (if any)

I recently ran into a bug which resulted from node-mysql returning fields in my production environment, but not in my staging environment. I was using async.auto and passed the step callback directly to mysql.query. In production, async.auto combined rows and fields into an arguments array, which lead to that part of the service breaking down because it got data in an unexpected format.

I could not get my staging environment to have fields be passed to the callback, and when I tried locally I could not get mysql to not pass fields. Is there any way to know when fields will be passed by mysql.query and when will it not?

Essentially

async.auto({
  runQuery: (next) => {
    mysql.query(sql, values, next);
  }
},
(err, results) => {
  // if `fields` is not passed to the callback by mysql.query,
  // then results.runQuery will be a row, or an array of rows -
  // [
  //   [
  //   [
  //     {
  //       "columnValue": 1
  //     }
  //   ],
  //   [
  //     {
  //       "columnValue": 1
  //     }
  //   ]
  // ]
  // 
  // instead, if `fields` is passed to the callback by mysql.query,
  // then results.queryQuery will be an array containing the row(s)
  // and the fields
  // 
  // [
  //   [
  //     [
  //       {
  //         "columnValue": 1
  //       }
  //     ],
  //     [
  //       {
  //         "columnValue": 1
  //       }
  //     ]
  //   ],
  //   [
  //     [
  //       {
  //         "catalog": "def",
  //         "db": "",
  //         "table": "",
  //         "orgTable": "",
  //         "name": "columnValue",
  //         "orgName": "",
  //         "charsetNr": 63,
  //         "length": 21,
  //         "type": 8,
  //         "flags": 129,
  //         "decimals": 0,
  //         "zeroFill": false,
  //         "protocol41": true
  //       }
  //     ],
  //     [
  //       {
  //         "catalog": "def",
  //         "db": "",
  //         "table": "",
  //         "orgTable": "",
  //         "name": "columnValue",
  //         "orgName": "",
  //         "charsetNr": 63,
  //         "length": 21,
  //         "type": 8,
  //         "flags": 129,
  //         "decimals": 0,
  //         "zeroFill": false,
  //         "protocol41": true
  //       }
  //     ]
  //   ]
  // ]
});