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MySQL InnoDB row lock

InnoDB is a storage engine for MySQL that provides robust transactional capabilities. One of its key features is row-level locking, which allows for high concurrency while maintaining the integrity of transactions.

Here's a basic tutorial on how you can use row-level locking in InnoDB:

SELECT ... FOR UPDATE: This command is a specific form of SELECT that sets a write lock on the selected rows. Other transactions can't update or delete these rows until your transaction commits.
Example:
```
START TRANSACTION;
SELECT * FROM employees WHERE employee_id = 1 FOR UPDATE;
```
This will lock the row where employee_id = 1 for updating, preventing other transactions from modifying this row until your transaction commits.
SELECT ... LOCK IN SHARE MODE: This command sets a read lock on the selected rows. Other transactions can read the rows, but can't update or delete them until your transaction commits.
Example:
```
START TRANSACTION;
SELECT * FROM employees WHERE employee_id = 1 LOCK IN SHARE MODE;
```
This will lock the row where employee_id = 1 for reading, preventing other transactions from modifying this row until your transaction commits.
Locking Read: Both SELECT ... FOR UPDATE and SELECT ... LOCK IN SHARE MODE are known as locking reads, because they set locks on the rows they retrieve.
Explicit Table Lock: While InnoDB uses row-level locks, you can still lock the entire table using LOCK TABLES if necessary.
Example:
```
LOCK TABLES employees WRITE;
```
This will lock the entire employees table for writing, preventing other transactions from reading or writing to it until you release the lock.
UNLOCK TABLES: This command is used to release any locks set by LOCK TABLES.
Example:
```
UNLOCK TABLES;
```
This will release any table-level locks you've set.

Remember that when you're using transactions with InnoDB, it's important to commit your transactions in a timely manner to release any locks and avoid causing unnecessary delays for other transactions.

How to detect and troubleshoot row locks in MySQL:
- Detect and troubleshoot row locks in MySQL by using tools like SHOW ENGINE INNODB STATUS to analyze the InnoDB status and identify transactions causing lock contention.
```
-- Check for row locks
SHOW ENGINE INNODB STATUS;
```
MySQL InnoDB lock modes for rows:
- InnoDB supports various lock modes for rows, including shared locks (SELECT ... FOR SHARE) and exclusive locks (SELECT ... FOR UPDATE).
```
-- Shared lock
SELECT * FROM my_table WHERE column1 = 'value' FOR SHARE;

-- Exclusive lock
SELECT * FROM my_table WHERE column1 = 'value' FOR UPDATE;
```

Row-level locking in concurrent MySQL transactions:

MySQL uses row-level locking to provide concurrent access to data. Transactions can lock individual rows to prevent conflicts.

-- Transaction 1
START TRANSACTION;
UPDATE my_table SET column1 = 'new_value' WHERE id = 1;
COMMIT;

-- Transaction 2
START TRANSACTION;
UPDATE my_table SET column1 = 'another_value' WHERE id = 1; -- Waits for lock
COMMIT;

Preventing conflicts with InnoDB row locks:
- Prevent conflicts with InnoDB row locks by optimizing queries, using appropriate indexes, and choosing the right isolation levels.
```
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
```