Why is it necessary to declare functions as suspend in the Room library for asynchronous operations?

In the Room library for database operations, input-output operations (such as database queries) can take a significant amount of time and block the main thread, leading to a 'freeze' of the interface. Declaring DAO functions as suspend uses Kotlin Coroutines, which allow these operations to be performed asynchronously without blocking the UI thread.

suspend functions can be called from coroutines, simplifying the writing of asynchronous code, making it more readable and maintainable, without the need to manually manage threads or use callbacks.

Example DAO with a suspend function:

@Dao
interface UserDao {
    @Query("SELECT * FROM users WHERE id = :id")
    suspend fun getUserById(id: Int): User
}

Thus, suspend helps to perform database operations safely and efficiently in the background.