Matters needing attention in transaction processing in PHP flash kill system

Transaction processing considerations in the PHP flash sale system

With the rapid development of e-commerce, flash sales have become a very popular shopping method, and major e-commerce companies The platform has launched various flash sale activities. For the platform, flash sales can bring higher sales and user stickiness, but it also comes with a series of challenges, one of which is how to handle competition for orders placed under high concurrency.

In the PHP flash sale system, transaction processing is a very critical link. Transaction processing can ensure the consistency and integrity of data and avoid problems such as repeated purchases and oversolds. This article will introduce transaction processing considerations in the PHP flash sale system and provide specific code examples.

1. Database Design and Optimization
   In the flash sale system, the database is an important part of carrying order and product information. In order to improve the concurrency capability of the system, the database needs to be designed and optimized accordingly. Here are some suggestions:

• Use InnoDB engine: InnoDB engine supports transaction processing and can ensure data consistency.
• Use indexes: Proper use of indexes can improve query efficiency and try to avoid full table scans.
• Avoid excessive normalization: Appropriate redundant data can reduce associated queries and improve performance.
• Use sub-databases and tables: Splitting data into multiple databases and tables can improve concurrency capabilities.

2. Optimistic locking and pessimistic locking
   In the flash sale system, common concurrency control methods include optimistic locking and pessimistic locking. Optimistic locking determines whether data conflicts by comparing version numbers or timestamps, while pessimistic locking directly locks to control concurrency.

Optimistic locking is suitable for situations where there is more reading and less writing. It can be achieved by using the optimistic locking mechanism of the database (such as version number) or a custom optimistic locking algorithm. The following is a Redis-based optimistic lock sample code:

<?php
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);

$productId = 123; // 商品ID
$userId = 456; // 用户ID
$quantity = 1; // 购买数量

if ($redis->setnx("lock:{$productId}", $userId)) {
    // 获取锁成功，执行秒杀逻辑
    $stock = $redis->get("stock:{$productId}");
    if ($stock >= $quantity) {
        $redis->decrby("stock:{$productId}", $quantity);
        $redis->rpush("order:{$userId}", $productId);
    }

    $redis->del("lock:{$productId}");
}

Pessimistic lock is suitable for situations where there are many writes and few reads, and can be implemented using the lock mechanism provided by the database (such as row locks and table locks). The following is a pessimistic lock sample code based on MySQL:

<?php
$mysqli = new mysqli('localhost', 'username', 'password', 'database');
$mysqli->autocommit(false); // 关闭自动提交事务

$productId = 123; // 商品ID
$userId = 456; // 用户ID
$quantity = 1; // 购买数量

$mysqli->query("SELECT * FROM `product` WHERE `id` = {$productId} FOR UPDATE");

$stock = $mysqli->query("SELECT `stock` FROM `product` WHERE `id` = {$productId}")->fetch_assoc()['stock'];
if ($stock >= $quantity) {
    $mysqli->query("UPDATE `product` SET `stock` = `stock` - {$quantity} WHERE `id` = {$productId}");
    $mysqli->query("INSERT INTO `order` (`user_id`, `product_id`) VALUES ({$userId}, {$productId})");
}

$mysqli->commit();
$mysqli->close();

3. Preventing oversold and repeated purchases
   In the flash sale system, oversold and repeated purchases are common problems. In order to avoid these problems, you can consider the following points:

• Non-inventory deduction operations must also be locked: Before obtaining inventory, you need to lock it first to prevent multiple users from deducting money at the same time. Reduce inventory.
• Unique constraints and idempotence processing: Avoid duplicate purchases by setting unique constraints in the database. At the same time, unique constraint errors need to be handled to ensure idempotence.
• Limit purchase frequency and quantity: Prevent overselling and repeated purchases by limiting the user's purchase frequency and quantity.

According to the specific business scenario, you can choose a suitable method to solve the problem of oversold and repeated purchases.

To sum up, transaction processing in the PHP flash sale system is a key link to ensure data consistency and integrity. Properly designing and optimizing the database, choosing appropriate concurrency control methods, and taking corresponding measures to prevent overselling and repeated purchases can improve the concurrency and stability of the system.

(Note: The above code examples are only demonstration examples, actual use needs to be appropriately modified and optimized according to specific business needs.)

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