Managing MySQL Deadlocks with Rollback and Retry

Handle Deadlocks

Write a MySQL query to handle a deadlock situation by retrying the transaction.

Solution:

-- Begin a new transaction to ensure atomicity and consistency
START TRANSACTION;

-- Update the salary of all employees in DepartmentID = 2 by increasing it by 10%:
-- Salary is multiplied by 1.1 to apply a 10% raise.
-- The WHERE clause ensures that only employees in Department 2 are affected.
UPDATE Employees 
SET Salary = Salary * 1.1 
WHERE DepartmentID = 2;

-- If a deadlock occurs, rollback the transaction to undo changes and allow a retry mechanism
ROLLBACK;

Explanation:

• Purpose of the Query:
• The goal is to demonstrate how to handle deadlocks by rolling back and retrying the transaction.
• Key Components:
• START TRANSACTION: Begins a new transaction.
• UPDATE Employees: Attempts to update salaries.
• ROLLBACK: Undoes the changes if a deadlock occurs.
• Why handle Deadlocks?:
• Deadlocks occur when two transactions block each other, and handling them ensures the system remains responsive.
• Real-World Application:
• For example, in a high-concurrency system, you might implement retry logic to handle deadlocks gracefully.

For more Practice: Solve these Related Problems:

• Write a MySQL query to simulate a deadlock scenario between two transactions.
• Write a MySQL query to resolve a deadlock by manually ordering operations in transactions.
• Write a MySQL query to detect and log deadlocks in a database.
• Write a MySQL query to implement a retry mechanism for deadlocks using stored procedures.

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Next MySQL Exercise: Use Savepoints in a Transaction.