title: How to define field names in Presto array_agg multiple columns
body: <p>When I use
  <code>array_agg((col_1, col_2, col_3))</code> in presto db, I get the output as</p>
  <p><code>[{field0=A, field1=112348.0, field2=22}, {field0=B, field1=10548.0, field2=2}, {field0=C, field1=19036.0, field2=4}]</code></p>
  <p>Instead of field0, field1 etc., I'd like to define my own names, so I get something like</p>
  <p><code>[{id=A, max_val=112348.0, num=22}, {id=B, max_val=10548.0, num=2}, {id=C, max_val=19036.0, num=4}]</code></p>