.java

// 가. 자식 객체 수동 삭제후 flush한 뒤 부모 삭제
List<Post> posts = entityManager.createQuery("select p from Post p join fetch p.comments", Post.class).getResultList();

// 자식 엔티티 먼저 삭제
for (Post post : posts) {
    post.getComments().clear(); // orphanRemoval=true이면 자동 삭제됨
}

entityManager.flush(); // 자식 DELETE 실행

// 부모 엔티티 삭제
for (Post post : posts) {
    entityManager.remove(post);
}
entityManager.flush(); // 부모 DELETE 실행



// 나. JPQL Bulk DELETE로 자식 엔티티 먼저 삭제
List<Post> posts = entityManager.createQuery("select p from Post p", Post.class).getResultList();

entityManager.createQuery("DELETE FROM PostComment c WHERE c.post IN :posts")
    .setParameter("posts", posts)
    .executeUpdate();

for (Post post : posts) {
    entityManager.remove(post);
}

entityManager.flush();



// 다. DB FK에 ON DELETE CASCADE 설정
ALTER TABLE post_comment
ADD CONSTRAINT fk_post_comment_post
FOREIGN KEY (post_id) REFERENCES post(id) ON DELETE CASCADE;

List<Post> posts = entityManager.createQuery("select p from Post p", Post.class).getResultList();

for (Post post : posts) {
    entityManager.remove(post); // Post만 삭제해도 DB가 자식(PostComment) 자동 삭제
}
entityManager.flush();