Implementing delete in columnar store fdw

Hello,

I want to implement delete functionality for a column store fdw in
postgres. It is similar to file_fdw. I want to use the
“AddForeignUpdateTargets” function to implement this , but the junk filter
shouldn’t be a column present in the table . Is it possible to add a
Expr/Var to the junk filter that is not present in the schema of the table
, that i will generate on the fly ??

If yes, how can i do that ?? Thanks in advance.

Regards,
Sri Harsha