@Entity
@Getter
@Setter
public class A {

  @Id
  @GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "ID_GENERATOR")
  @SequenceGenerator(name="ID_GENERATOR",sequenceName = "a_id_seq")
  private Long id;

  private String name;

create sequence a_id_seq increment 50;
create table A(
  id bigint DEFAULT nextval('a_id_seq') primary key ,
  name text
);

 public List<A>getTestListA(){
    List<A> aList = new ArrayList<>();
    for (int i = 0; i < 100; i++) {
      A a = new A();
      a.setName("a" + i);
//      a.setBList(getTestListB());
      aList.add(a);

    }
    return aList;
  }

 @PostMapping
  public String saveAllTest(){
    var list=batchTestingService.getTestListA();
    aRepository.saveAll(list);
    return "OK";
  }

3193301 nanoseconds spent preparing 3 JDBC statements;
    390061405 nanoseconds spent executing 2 JDBC statements;
    431665399 nanoseconds spent executing 1 JDBC batches;

  @PutMapping
  public String updateAllTest(){
    var list=aRepository.findAll();
    for (int i = 0; i <list.size() ; i++) {
      list.get(i).setName("A"+i);

    }
    aRepository.saveAll(list);
    return "OK";
  }

3193301 nanoseconds spent preparing 101 JDBC statements;
    390061405 nanoseconds spent executing 100 JDBC statements;
    431665399 nanoseconds spent executing 1 JDBC batches;