Java springboot - Best way to structure my Object relationships for performance?

Question

I am using SQL & Java Springboot.

In my design, content is stored in modules & content have quite a few different variations.

Content can only be designated to a single module, once content is created it cannot updated to another module because different admin users have separated access to different module moderation.

The way activities are stored is with a foreign key table between, eg. extra & module.

    @OneToMany
    @JoinTable(name="module_extras",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "extra_id")
    )
    private List<Extra> extras = new ArrayList<>();

Because it is stored this way, every time I want to get only extra or a list of only extra, (which is a quite common use case as I have a designated area for it) it must:

1. Recursively loop to get each extra requested, temporarily convert it to a DTO.
2. Recursively loop over each module, checking if the extra is contained inside it.
3. If it find the corresponding extra to module, appending the module.code to the extra-moduledto.
4. then reply with all the extra-moduledto requested.

Given it must loop this logic, for every module and for all content's inside module (when called for content sections independently), potentially many, many times to support users refreshing & interacting with content, this seems like it would be bad on performance & has a multiple points of potential failure / errors.

The alternate solution I am considering is adding a moduleCode column to each content, like extra and demolish the relationship.

1.While it would take more storage doing this ^, would performance be better from doing far less number of operations?

2. Is the above solution against convention?

If anybody has any suggestions or thoughts that may be useful from your own experience it would be greatly appreciated.

Module Class:

@Data @NoArgsConstructor @AllArgsConstructor @Entity
@Table(name = "module")
public class Module {
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(unique=true)
    private String code;

    @Nullable
    private String name;

    @ManyToMany
    @JoinTable(name="module_students",
       joinColumns = @JoinColumn(name="module_id"),
       inverseJoinColumns =  @JoinColumn(name = "user_id")
    )
    private Set<User> students = new HashSet<>();

    @ManyToMany
    @JoinTable(name="module_admins",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "user_id")
    )
    private Set<User> admins = new HashSet<>();

    @OneToMany
    @JoinTable(name="module_quizzes",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "quiz_id")
    )
    private List<Quiz> quizzes = new ArrayList<>();

    @OneToMany
    @JoinTable(name="module_hangmen",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "hangnman_id")
    )
    private List<Hangman> hangmen = new ArrayList<>();

    @OneToMany
    @JoinTable(name="module_extras",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "extra_id")
    )
    private List<Extra> extras = new ArrayList<>();

    @OneToMany
    @JoinTable(name="module_matches",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "match_id")
    )
    private List<Match> matches = new ArrayList<>();

    @OneToMany
    @JoinTable(name="module_feedbacks",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "feedback_id")
    )
    private List<Feedback> feedbacks = new ArrayList<>();

    @OneToMany
    @JoinTable(name="module_swipes",
            joinColumns = @JoinColumn(name="module_id"),
            inverseJoinColumns =  @JoinColumn(name = "swipe_id")
    )
    private List<Swipe> swipes = new ArrayList<>();