add e2e for drop function

Signed-off-by: Richard Chien <[email protected]>

e2e_test/udf/drop_function.slt

@@ -0,0 +1,55 @@
+# https://github.com/risingwavelabs/risingwave/issues/17263
+
+statement ok
+create table t (a int, b int);
+
+statement ok
+create function add(a int, b int) returns int language python as $$
+def add(a, b):
+  return a+b
+$$;
+
+statement ok
+create materialized view mv as select add(a, b) as c from t;
+
+statement error
+drop function add;
+----
+db error: ERROR: Failed to run the query
+
+Caused by:
+  Permission denied: PermissionDenied: function used by 1 other objects.
+
+
+statement ok
+drop materialized view mv;
+
+statement ok
+drop function add;
+
+
+statement ok
+create function add(a int, b int) returns int language python as $$
+def add(a, b):
+  return a+b
+$$;
+
+statement ok
+create sink s as select add(a, b) as c from t with (connector = 'blackhole');
+
+statement error
+drop function add;
+----
+db error: ERROR: Failed to run the query
+
+Caused by:
+  Permission denied: PermissionDenied: function used by 1 other objects.
+
+statement ok
+drop sink s;
+
+statement ok
+drop function add;
+
+statement ok
+drop table t;