How to get the real column name and data type from a SQL view ?

[Armstrong]

Hi guys,
     Thanks for your time to read this help message. I'm new to Calcite and
reading some codes and examples from calcite Github repo. I'm wandering how
to get the column real name and type from view.
     For example, I have some SQL as below.  A kafka topic table left join
MySQL table, and use a View join_result_view represent the join result. I
want to get the real column name and data type from this view.
     How to get  result like this ? "user_id", bigint ;  "log_time", bigint
     I already try use SqlParse parse these sqls, and get the SqlNode, but
I can't get the real column name and type. Maybe I missed out the correct
method. Hopefully some one can identify the problem, thanks a lot.

CREATE TABLE user_action_source (
    `user_id` STRING,
    `item_id` BIGINT,
    `bhv_type` STRING,
    `bhv_time` INT,
    `play_duration` INT,
    `ts` BIGINT,
    proc_time as PROCTIME()
) WITH (
        'connector' = 'kafka',
        'topic' = 'user_action_log',
        'parallelism' = '5',
        'properties.cluster' = 'asv_cluster',
        'properties.group.id' = 'demo-job',
        'scan.startup.mode' = 'latest-offset',
        'format' = 'json',
        'json.fail-on-missing-field' = 'false',
        'json.ignore-parse-errors' = 'true',
        'scan.manually-commit-offsets-interval' = '5000'
);

CREATE TABLE item_source (
    `item_id` BIGINT,
    `video_name` STRING,
    `video_count` INT,
    `video_duration` INT,
    `authors` STRING
) WITH (
    'connector' = 'jdbc',
    'url' = 'jdbc:mysql://localhost:3306/mydatabase',
    'table-name' = 'item_info'
);

create view join_result_view as
select a.user_id, a.item_id, a.bhv_type, a.ts as log_time, b.video_name,
b.video_count, b.video_duration, b.authors
from user_action_source  as a left join item_source  FOR SYSTEM_TIME AS OF
a.proc_time as b
on a.item_id = b.item_id;