HSQLDB 删除触发器导致子查询出现问题

Question

我在 HSQLDB 删除触发器中遇到问题，不知何故它没有按预期工作。

我正在尝试实现数据库中每次更改的日志。

对于示例测试，我执行以下 SQL 语句：

CREATE TABLE msg (
  id INTEGER IDENTITY PRIMARY KEY,
  name VARCHAR(80)
);

CREATE TABLE log (
    id INTEGER IDENTITY PRIMARY KEY,
    row_id INTEGER,
    op VARCHAR(30),
    status VARCHAR(30)
);

insert into msg (id, name) values (0, 'First Test Message');
insert into log (id, row_id, op, status) values (0, 0, 'insert', 'pending');

update log set status = 'done' where id = 0;

现在，我创建一个删除触发器并从msg 表中删除行：

CREATE TRIGGER update_log_delete_msg
AFTER DELETE ON msg REFERENCING OLD ROW AS old_row FOR EACH ROW
BEGIN ATOMIC
    INSERT INTO log(row_id, op, status)
    SELECT old_row.id, 'delete', CASE status WHEN 'pending' THEN 'cancel' ELSE 'pending' END FROM log
    WHERE row_id = old_row.id AND NOT status = 'cancel' ORDER BY id DESC LIMIT 1;

    UPDATE log SET status = 'cancel'
    WHERE row_id = old_row.id AND op = 'insert' AND status = 'pending';
END

delete from msg where id = 0;

到目前为止，它按预期工作：

insert into msg values (0, 'Test Message Again');
insert into log (row_id, op, status) values (0, 'insert', 'pending');

这个，时间删除会出问题：

delete from msg where id = 0;

日志中状态的预期行为应该是cancel而不是pending，为什么会导致问题？

Answer 1

如果您不重复使用 ID 值零，这似乎可行。当您重用该值时，log 表中的旧行会导致意外结果。

insert into msg values (1, 'Test Message Again');
insert into log (row_id, op, status) values (1, 'insert', 'pending');
delete from msg where id = 1;                                        

-- dump of the log table

0,0,insert,done
1,0,delete,pending
2,1,insert,cancel
3,1,delete,cancel