PostgreSQL: create aggregate method iterating over json

Using the data below ``` create table my_table (my_column json); insert into my_table values ('{"total": 10, "custom": 1}'::json), ('{"total": 9, "custom": 2}'::json), ('{"total": 21, "custom": 7}'::json), ('{"total": 11, "custom": 9}'::json), ('{"total": 12, "custom": 10}'::json); ``` Objective: Create 3 methods to aggregate the data in the manner below. ``` select max_json_key('total', my_column) from my_table; # results in {"total": 21, "custom": 7} select min_json_key('total', my_column) from my_table: # results in {"total": 9, "custom": 2} select avg_json_key('total', my_column) from my_table: # results in {"total": 12, "custom": 10} ``` - The resulting value returns the full json object for the corresponding value. - keys are not aggregated, only the "totals" key is used to determine which entry fits the criteria. Thank you!