使用 php 和 mysql 每个字段的唯一序列

问题描述

在给定的表中，我必须填写：pos（销售点）和凭证_编号。

它们都分组在一个唯一索引中

例如，我需要每个 pos 有一个唯一的序列

ID	日期	位置	voucher_number
1	2021-01-01 11:45:37	1	1
2	2021-01-01 17:22:45	1	2
3	2021-01-02 15:08:02	2	1
4	2021-01-02 15:08:02	1	3
5	2021-01-03 10:37:24	2	2
6	2021-01-03 10:37:24	3	1
7	2021-01-03 10:37:24	1	4

不同的用户可以同时创建不同的凭证，所以我关心的是如何确保顺序保持自然顺序，不重复或跳过数字

我正在处理的代码包含在一个事务中，我正在考虑做这样的事情（伪）：

//At this point a transaction has already been started

function save_voucher($voucher_data)
{
    //Notice the SELECT ... FOR UPDATE
    $max_voucher_number = select max(voucher_number) as max_voucher_number from vouchers where pos = $voucher_data["pos"] for update;

    $voucher_data["voucher_number"] = $max_voucher_number + 1;
    
    //I can't alter save_voucher() in parent class
    //But inside it would perform something like:
    //insert into (pos,voucher_number) values ($voucher_data["pos"],$voucher_data["voucher_number"]);
    return parent::save_voucher($voucher_data);
}

//After the method execution,a commit or rollback happens;

甚至类似：

//At this point a transaction has already been started

function save_voucher()
{
    //I can't alter save_voucher() in parent class
    $new_voucher_id = parent::save_voucher();

    //Now,after a voucher had been created I could get the max sequence
    //Notice the SELECT ... FOR UPDATE
    $max_voucher_number = select max(voucher_number) as max_voucher_number from vouchers where pos = $pos for update;

    //Then,I could update that voucher
    update vouchers set voucher_number = $max_voucher_number + 1 where id = $new_voucher_id;

    return $new_voucher_id;
}

//After the method execution,a commit or rollback happens;

以上是否可以保证每个 pos 都有唯一的序列？可能的并发是否会以任何方式影响序列？

我将 MySQL 与所有使用 InnoDB 的表一起使用

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

如果你已经找到好的解决方法，欢迎将解决方案带上本链接一起发送给小编。

小编邮箱:dio#foxmail.com (将#修改为@）

mysql transactions unique-key