The way to get all columns used in current SQL from source tables

Question

I intend to get the list of all columns used in current SQL from all source tables. For instance:

Table X(int a, String b, String e)
Table Y(String c, String d)

SELECT
    X.a
    Y.c
from X
join Y on X.b = Y.c
...
;

Then the expected output should be {"X": ["a","b"], "Y": ["c"]}, X.e and Y.d should not appear in the result since they are not used in the previous SQL.

Any idea how to achieve this in Flink SQL? Thanks.