在删除之前触发低性能

Question

我正在使用SQLite数据库连接在QT Creator中编写C ++应用程序。我想要实现的是，当我从表中删除一行时，其他引用它的表中的行也会被删除。所以在我的情况下，如果我从Basket中删除一行，则从计算机中引用行也会被删除，然后从子系统，订阅者，规则等中删除，直到结束。

这是我的数据库图表：

我为每个具有其他表的外键引用的表创建了触发器。

CREATE TRIGGER delete_fk BEFORE DELETE ON Basket
FOR EACH ROW BEGIN 
    DELETE FROM Computer WHERE computer.basket = old.id_basket;
END

CREATE TRIGGER delete_fk_comp BEFORE DELETE ON computer
FOR EACH ROW BEGIN
    DELETE FROM subsystemtable WHERE subsystemtable.computer = id.id_computer;
END

CREATE TRIGGER delete_fk_subscriber_map BEFORE DELETE ON subscriber
FOR EACH ROW BEGIN 
    DELETE FROM mappingtable WHERE mappingtable.subscriber = old.id_subscriber;
END

CREATE TRIGGER delete_fk_subscriber_indirect BEFORE DELETE ON subscriber
FOR EACH ROW BEGIN
    DELETE FROM indirectsubscriber WHERE indirectsubscriber.subscriber = old.id_subscriber;
END

CREATE TRIGGER delete_fk_subscriber BEFORE DELETE ON subscriber
FOR EACH ROW BEGIN
    DELETE FROM reserve WHERE reserve.subscriber = old.id_subscriber;
END

CREATE TRIGGER delete_fk_subscriber_res BEFORE DELETE ON subscriber
FOR EACH ROW BEGIN
    DELETE FROM reserve WHERE reserve.subscriber_res = old.id_subscriber;
END

CREATE TRIGGER delete_fk_subs BEFORE DELETE ON subsystem
FOR EACH ROW BEGIN
    DELETE FROM subsystemtable WHERE subsystemtable.subsystem = old.id_subsystem;
END

CREATE TRIGGER delete_fk_substable_reg BEFORE DELETE ON subsystemtable
FOR EACH ROW BEGIN
    DELETE FROM regulations WHERE regulations.subsystem = old.id;
END

CREATE TRIGGER delete_fk_substable BEFORE DELETE ON subsystemtable
FOR EACH ROW BEGIN 
    DELETE FROM subscriber WHERE subscriber.subsystem = old.id;
END

我得到了我想要的东西。它的工作原理与我想要的完全一样。但我现在的问题是性能低下。所以在我的数据库中，每个篮子大约有20台计算机，每台计算机大约有5个子系统，每个子系统有100个用户，等等。当我删除1个单篮时，整个过程大约需要400毫秒。我应该一次删除3个篮子，已经花了3秒多。

我需要找到一种方法让它更快地发挥作用。我想，限制在200-300毫秒左右。我需要任何关于如何做的建议。

Answer 1

您正在手动实施外键。 这不是必要的;您可以使用ON DELETE actions让DB进行适当的更改。

无论是手动实现外键还是在数据库的帮助下，都需要创建indexes on certain key columns，否则查找相关行所需的所有查找都会很慢。