populate_recordset.sql

do $$
declare 
    _rawjson json;
    _item    record;
    _id      int;
    _param   text;
begin
    for _rawjson in select * from json_array_elements('[{"id" : 42, "params" : ["bad", "sad"] }]'::json) loop 
            _item = (select j from json_to_record(_rawjson) AS j (
                    id     int, 
                    params json
                )
            );

        for _id, _param in select _item.id, _p from json_array_elements_text(_item.params) as _p  loop 
            raise info 'id: %, param: %', _id, _param;
        end loop;   
    end loop;
end $$;