Can you explain how data reading is performed in read-only transaction mode?

The read-only transaction mode is used to optimize database operations when it is necessary to guarantee that data will not be modified within the transaction.

In Java, for example, when using the Spring Framework, you can specify the attribute readOnly = true in the @Transactional annotation:

@Transactional(readOnly = true)
public List<User> getAllUsers() {
    return userRepository.findAll();
}

This informs the transaction management system and the database that no write operations will occur within this transaction. This can lead to:

• Query optimization (for example, the database may use less strict locking).
• Prevention of accidental data modifications.

It is important to understand that behavior depends on the specific database and driver, but overall, this is a good way to explicitly indicate the intention to only read data within a transaction.