public interface ImageRepository extends JpaRepository<Image, Long> {

}

public interface ProductRepository extends JpaRepository<Product, Long> {

    List<Product> findAllByName(String name);

    @Query("SELECT p FROM Product p " +
            "LEFT JOIN FETCH p.categories " +
            "LEFT JOIN FETCH p.brand " +
            "LEFT JOIN FETCH p.images " +
            "LEFT JOIN FETCH p.tags " +
            "LEFT JOIN FETCH p.relations " +
            "LEFT JOIN FETCH p.mainImage " +
            "WHERE p.id = (:id)")
    Optional<Product> findByIdAndFetchAllEagerly(@Param("id") Long id);
}

@Service
public class ProductService {

    private final ProductRepository productRepository;
    private final ImageRepository imageRepository;

    public ProductService(ProductRepository productRepository, ImageRepository imageRepository) {
        this.productRepository = productRepository;
        this.imageRepository = imageRepository;
    }

    @Transactional
    public Product deleteImage(Long productId, Long imageId) {

        final Product product = productRepository
                .findByIdAndFetchAllEagerly(productId)
                .orElseThrow(() -> new EntityNotFoundException("Product with id = " + productId + " not found"));

        final Image image = imageRepository
                .findById(imageId)
                .orElseThrow(() -> new EntityNotFoundException("Image with id = " + imageId + " not found"));

        product.getImages().remove(image);

        // unlink main image
        if (product.getMainImage() != null && product.getMainImage().equals(image)) {
            product.setMainImage(null);
        }

        productRepository.save(product);
        imageRepository.delete(image);

        return product;
    }

}

public interface ProductRepository extends JpaRepository<Product, Long> {

    List<Product> findAllByName(String name);

    @Query("SELECT p FROM Product p " +
            "LEFT JOIN FETCH p.categories " +
            "LEFT JOIN FETCH p.brand " +
            "LEFT JOIN FETCH p.images " +
            "LEFT JOIN FETCH p.tags " +
            "LEFT JOIN FETCH p.relations " +
            "LEFT JOIN FETCH p.mainImage " +
            "WHERE p.id = (:id)")
    Optional<Product> findByIdAndFetchAllEagerly(@Param("id") Long id);
}