presto

1. json_parse, json_extract
   https://prestodb.io/docs/current/functions/json.html?highlight=json_parse#json_parse
2. 先将json通过cast成为map,再对map应用map_entries,map_values,transform_keys,transform_values之类的函数，提取出key和value的数组，再对数组应用transform函数，通过lambda表达式进行转换。
   https://prestodb.io/docs/current/functions/map.html
   https://prestodb.io/docs/current/functions/array.html