POSTGRES - Risk of dropping foreign data wrapper/schema - sql

Question

We had one of the devs create a foreign data wrapper with these commands:
CREATE SERVER serverName FOREIGN DATA WRAPPER postgres_fdw OPTIONS (xxxx);
CREATE USER MAPPING FOR user SERVER foreign_db OPTIONS (user 'xxxx', password 'xxxx');
CREATE SCHEMA foreign_db;
IMPORT FOREIGN SCHEMA public FROM SERVER serverName INTO foreign_db;
To drop this schema the suggestion was to run:
DROP SCHEMA if exists foreign_db cascade;
DROP USER mapping if exists for user server foreign_db;
DROP SERVER if exists serverName;
In the spec I see this for CASCADE:
Automatically drop objects (tables, functions, etc.) that are
contained in the schema, and in turn all objects that depend on those
objects
what concerns me is this line:
and in turn all objects that depend on those objects
My question is there a possibility of dropping anything outside of foreign_db schema and if yes, how can I check it?
Thank you.

Answer 1

It is possible that the command drops something outside the schema. Consider this:
create schema example;
create table example.my_table (id int);
create view public.my_view as select * from example.my_table;
If the schema is dropped with the cascade option, public.my_view will also be dropped. However, the behavior is logical and desirable.
You can check this executing these commands one by one:
begin;
drop schema example cascade;
rollback;
The schema will not be dropped and after drop... you should get something like this:
NOTICE: drop cascades to 2 other objects
DETAIL: drop cascades to table example.my_tabledrop cascades to view my_view
Alternatively, you can use the system catalog pg_depend, see this answer How to list tables affected by cascading delete.