hibernate join fetch dump result

Question

I am new to the hibernate. Can some one explain why the first query gets the dump results? thanks!

shop entity

....
@OneToMany(mappedBy = "shop")
private Collection<Product> productCollection;
....

product entity

....
 @JoinColumn(name = "shopId", referencedColumnName = "id")
@ManyToOne
private Shop shop;
....

query1 result

from Shop s left join fetch s.productCollection

shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop1 : product1 product2 product3 product4 product5 product6 product7 product8 product9 product10 product11 
shop2 : product12 

query2 result

from Product p right join fetch p.shop

 product1 : shop1
product2 : shop1
product3 : shop1
product4 : shop1
product5 : shop1
product6 : shop1
product7 : shop1
product8 : shop1
product9 : shop1
product10 : shop1
product11 : shop1
product12 : shop2

ps. if you need more information, please let me know.

Answer 1

Use natural join instead of left outer join. This is happening because you have shop1 in multiple products. For every product it will try to join with shop1.

Edit 1: Another JPA provider( hibernate ) specific solution is using private Set<Product> productCollection; instead of private Collection<Product> productCollection; That will fetch unique result.

Hope it works.