MYSQL implements sample code to prevent duplicate addition when adding shopping cart

Preface

Recently, due to work reasons, I was working on the APP shopping cart order payment. A bug was found during testing. When I clicked Add to Cart quickly, the same product appeared twice in the shopping cart.

Because when adding to the shopping cart, there are two steps. The first step is to determine whether the product to be added to the shopping cart is already in the shopping cart. If it is, add one to the original quantity. If not, add it again.

Because the two steps are not atomic operations, there is a multi-threaded security issue. I won’t say much below. Let’s follow the editor to look at the detailed solution process, which will be of some help to you.

MySQL insert has a more advanced operation

Sample code:

INSERT INTO t_xs_shopping_cart (
 user_id,
 shop_id,
 commodity_id,
 quantity
)
VALUES 
 (71, 67, 140201057403511024, 1) ON DUPLICATE KEY UPDATE quantity = quantity + 1

When the unique key constraint takes effect, the update statement will be executed to increase the quantity by 1

Summarize

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