Tell me about transaction isolation levels

Transaction isolation levels determine how much a transaction can see the changes made by other transactions and help prevent issues with concurrent data access. The main isolation levels are:

• Read Uncommitted — the lowest level of isolation. A transaction can see uncommitted changes made by other transactions (dirty read).
• Read Committed — a transaction only sees changes that have been committed. It avoids dirty reads but allows non-repeatable reads.
• Repeatable Read — guarantees that data read during a transaction will not change until the transaction completes. It prevents non-repeatable reads but allows phantom reads.
• Serializable — the strictest level. Transactions are executed as if they were sequential, fully preventing phantom reads and other anomalies.

Example of setting the isolation level in Kotlin using Spring:

@Transactional(isolation = Isolation.REPEATABLE_READ)
fun someDatabaseOperation() {
    // operation code
}

The choice of isolation level depends on the system's requirements for consistency and performance.