Query a limited items from the database

Question

I'm working on a Spring application and I need to update every user in a database (around 4500 records).

My code works well in my local environment with a few users, but I'm afraid in the testing environments and even in live it will be extremly slow if I get every user from the database.

Here is my code so far:

public void syncUsers() {
        List<User> usersList = userService.getAllUsers();
        usersList.stream().forEach((user) -> {
            if (isNull(user.getSocialId())) {
                String id = socialRestAPIService.syncContacts(user);
                user.setSocialId(id);
                userService.updateUser(user);
            }
        });
    }

This one is the userService.getAllUsers method:

public List<User> getAllUsers () {
        return userRepository.findAll();
    }

What I want to achive is update 100 users in one time and then update the next 100 so on... How is it possible?

Answer 1

If the userRepository is a JpaRepository then it implements the PagingAndSortingRepository which has a method findAll(Pageable pageable).

Hence, you can create a Pageable like this:

Pageable.ofSize(100).withPage(10)