One user reported a issues with triggers related to dropped columns.
When I checked his code, I found a more possible problems.
He use a trigger in form
$$
DECLARE somevar targettable;
BEGIN
somevar := NEW;
// do some with somevar;
RETURN somevar;
END;
$$
When I dropped column (I dropped numeric column) I had to finish session, because I got a error in assign
LOCATION: exec_stmt_raise, pl_exec.c:2985 ERROR: 22P02: invalid input syntax for type numeric: "aaa" CONTEXT: PL/pgSQL function f1_trg() line 4 at assignment LOCATION: set_var_from_str, numeric.c:3253