MySQL create after insert trigger fails foreign key constraint - mysql

Question

I have 3 tables:
create table users (
id int auto_increment primary key,
first_name varchar(40) not null,
last_name varchar(40) not null,
email varchar(40) not null,
password varchar(40) not null,
deleted tinyint(1) not null default 0
) engine = InnoDB;
create table comments (
id int auto_increment primary key,
task_id int not null,
foreign key fk_comment_task(task_id) references tasks(id),
user int not null,
foreign key fk_comment_user(user) references users(id),
comment varchar(1000) not null,
comment_date date not null,
viewed tinyint(1) not null default 0,
deleted tinyint(1) not null default 0
) engine = InnoDB;
create table viewed_comments (
id int auto_increment primary key,
comment int not null,
foreign key fk_viewed_comment(comment) references comments(id),
viewer int not null,
foreign key fk_viewed_viewer(viewer) references users(id),
unread tinyint(1) not null default 0,
deleted tinyint(1) not null default 0
) engine = InnoDB;
I made a trigger that creates rows in viewed_comments for every user in the users table that is not the user that submitted the comment:
delimiter |
create trigger ins_views after insert on comments
for each row
begin
DECLARE finished INT DEFAULT 0;
DECLARE id INT DEFAULT 0;
DECLARE currentId CURSOR FOR SELECT id FROM users WHERE id != NEW.user;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET finished = 1;
OPEN currentId;
update_views_loop: LOOP
FETCH currentId INTO id;
IF finished = 1 THEN LEAVE update_views_loop; END IF;
INSERT INTO viewed_comments (comment, viewer) VALUES (NEW.id, id);
END LOOP update_views_loop;
CLOSE currentId;
END;
|
delimiter ;
The problem is that when I try to insert a comment such as
insert into comments (task_id, user, comment, comment_date) values (24, 6, 'test', '2018-3-5');
It fails saying the 'Cannot add or update a child row: a foreign key constraint fails (viewed_comments, CONSTRAINT fk_viewed_viewer FOREIGN KEY (viewer) REFERENCES users (id)). When I change the trigger on the insert line to the following it works to a degree:
INSERT INTO viewed_comments (comment, viewer) VALUES (NEW.id, 6);
On this sample set I have 3 users, and on the viewed_comments table I get 3 new rows, instead of 2. I'm not sure how to troubleshoot this in MySQL or how to print the variables to see the values as it happens. It seems on the cursor line New keyword is disregarded resulting in 3 rows instead of 2. But, then it has a value on the insert statement, but the cursor doesn't have any values. I am using MariaDB 10.4.11 How do I fix this?