drop_swap can drop triggers

drop table if exists bbb;
drop table if exists aaa;
CREATE TABLE aaa (
 id int NOT NULL AUTO_INCREMENT,
 c int DEFAULT NULL,
 z int DEFAULT NULL,
 PRIMARY KEY (`id`),
 CONSTRAINT `FK_z` FOREIGN KEY (`z`) REFERENCES aaa (`id`)
);
CREATE TABLE bbb (
 id int NOT NULL AUTO_INCREMENT,
 aaa_id int DEFAULT NULL,
 modification_date datetime(3),
 PRIMARY KEY (`id`),
 CONSTRAINT `FK_aaa_id` FOREIGN KEY (`aaa_id`) REFERENCES aaa (`id`)
);

CREATE TRIGGER before_aaa_upd BEFORE UPDATE ON aaa FOR EACH ROW set new.c = old.c+1;
 DELIMITER $$
CREATE TRIGGER after_aaa_upd AFTER UPDATE ON aaa FOR EACH ROW BEGIN UPDATE bbb SET modification_date = UTC_TIMESTAMP(3) WHERE aaa_id = NEW.id; END;
$$
DELIMITER ;

select definer, trigger_name name, action_timing timing, event_manipulation manip, event_object_table tbl, action_statement stmt
-- , "]---[", T.* 
from information_schema.triggers T
where trigger_schema = database() and (event_object_table like 'aaa%' or event_object_table like 'bbb%') ;

insert into aaa (c) values (10),(20),(30),(40),(50);
 SELECT * FROM aaa;
 insert into bbb (aaa_id) values (2), (2), (3), (3);
 SELECT * FROM bbb;
 update aaa set z=id where id=2;
 SELECT * FROM bbb; -- modification_date should appear on 2 rows

 ./ptosc/bin/pt-online-schema-change -h _________ -P 3306 -u _______ -p ________
 D=mydatabase,t=aaa 
 --execute --statistics --print --no-version-check
 --preserve-triggers 
 --alter-foreign-keys-method drop_swap 
 --alter 'ADD COLUMN f2 int(11) default 42' 

select definer, trigger_name name, action_timing timing, event_manipulation manip, event_object_table tbl, action_statement stmt 
from information_schema.triggers T
where trigger_schema = database() and (event_object_table like 'aaa%' or event_object_table like 'bbb%') ;

update aaa set z=id where id=3;
SELECT * FROM bbb; /* modification_date should appear on 2 more rows */