Spring JPA：@OrderBy 在使用 saveAndFlush 时不起作用

Question

I am using @OrderBy clause on my bean this works fine when i am getting this object from the persistence layer, but when i try to save this data using

persistedObject = saveAndFlush(MyCustomObject);

Results in persistedObject are not sorted as specified by @OrderBy clause.

Code snippet :

@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
@JoinColumn(name = "COLLECTION_ID")
@OrderBy("order ASC")
private Set<MySections> sections;

class MySections {
  // Some Properties
    @Column(name = "SEQ_NO")
    private Integer order;
}

Repository related code

// this brings sections ordered by order property
collectionRepository.findById("123"); 


// Sections in persistedCollection are not ordered
persistedCollection = collectionRepository.saveAndFlush(collection); 

Answer 1

It's because @OrderBy does not materialize the order directly in database. It fetches the data and performs sorting in memory. To achieve, what you have described you would have to use @OrderColumn . It maintains the persistent order of rows in database.

One more advice - using just select queries is not a good option to check for ordering as database does not assure about the ordering of the result.