QueryDSL is not working properly with JPA for left join.
I am using queryDSL version 4.2.1 and mapping the response directly to javax.persistence entity.
For Left join/Right join, the joining condition it's not working. It fetches every entity disregarding the joining condition(here it's name = "testName") when entity1.getEntity2() is being called.
Is there any other way applicable for this case to map the result after JOIN tables ?
JPAQuery<Entity1> query = new JPAQuery<>(entityManager);
query.from(table1);
query.leftJoin(table2).on(table2.id.eq(table1.id).and(table2.name.eq("testName"));
List<Entity1> list = query.fetch();
#Entity
public class Entity1{
private Integer id;
#OneToMany(mappedBy = "entity1", fetch = FetchType.LAZY)
private List<Entity2> entity2;
}
An left or right join is an outer join.
So if you use left join all records from the left (in your case table1) will be selected.
If you only want records from table1 if there are corresponding records on table2 you have to use innerJoin.
JPAQuery<Entity1> query = new JPAQuery<>(entityManager);
query.from(table1);
query.innerJoin(table2).on(table2.id.eq(table1.id).and(table2.name.eq("testName"));
List<Entity1> list = query.fetch();
Read more about the join types here:
https://www.diffen.com/difference/Inner_Join_vs_Outer_Join
Related
I have an Entity with a ManyToOne Relationship to the Primary Key of another entity. When I create a query that references this Foreign Key eclipseLink always creates a join instead of simply accessing the Foreign Key.
I have created a highly simplified example to show my issue:
#Entity
public class House {
#Id
#Column(name = "H_ID")
private long id;
#Column(name = "NAME")
private String name;
#ManyToOne
#JoinColumn(name = "G_ID")
private Garage garage;
}
#Entity
public class Garage{
#Id
#Column(name = "G_ID")
private long id;
#Column(name = "SPACE")
private Integer space;
}
I created a query that should return all houses that either have no garage or have a garage with G_ID = 0 using the CriteriaBuilder.
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<House> query = cb.createQuery(House.class);
Root<House> houseRoot = query.from(House.class);
Path<Long> garageId = houseRoot.get(House_.garage).get(Garage_.id);
query.where(cb.or(cb.equal(garageId , 0), cb.isNull(garageId)));
TypedQuery<House> typedQuery = entityManager.createQuery(query);
List<House> houses = typedQuery.getResultList();
The generated query is:
SELECT h.NAME, h.G_ID FROM HOUSE h, GARAGE g WHERE (((h.G_ID= 0) OR (g.G_ID IS NULL)) AND (g.G_ID = h.G_ID));
I don't understand why
The or condition first references table HOUSE and then GARAGE (instead of HOUSE)
The join is created in the first place.
The correct query should look like this in my understanding:
SELECT h.NAME, h.G_ID FROM HOUSE h WHERE (((h.G_ID= 0) OR (h.G_ID IS NULL));
Or if a join is made it should take into account that the ManyToOne relationship is nullable and therefore do a LEFT OUTER JOIN.
SELECT h.NAME, h.G_ID FROM HOUSE h LEFT OUTER JOIN GARAGE g ON (h.G_ID = g.G_ID ) WHERE (h.G_ID = 0) OR (g.G_ID IS NULL);
(Note both these queries would work correctly in my more complicated setup. I also get the same error when only wanting to retrieve all houses that have no garage.)
How can I achieve this (while still using the CriteriaBuilder and ideally not having to change the DB Model)?
(Please let me know any additional information that might be required, I'm very new to this topic and came across this issue while migrating an existing application.)
-- edit --
I have found a solution to my problem that will result in slightly different behaviour (but in my application that part of the code I had to migrate didn't make much sense in the first place). Instead of using
Path<Long> garageId = houseRoot.get(House_.garage).get(Garage_.id);
I use
Path<Garage> garage = houseRoot.get(House_.garage);
And then as expected table Garage isn't joined anymore. (I assume the code previously must have been some kind of hack to get the desired behaviour from openJPA)
I don't understand why
The or condition first references table HOUSE and then GARAGE (instead of HOUSE)
I believe this is implementation specific; in any case, it shouldn't have any bearing on the results.
The join is created in the first place.
By saying Path<Long> garageId = houseRoot.get(House_.garage).get(Garage_.id) you're basically telling EclipseLink: 'join Garage to House, we're gonna need it'. That you then access Garage_.id (and not, for example, Garage_.space) is inconsequential.
If you don't want the join, simply map the G_ID column one more time as a simple property: #Column(name = "G_ID", insertable = false, updatable = false) private Long garageId. Then refer to House_.garageId in your query.
Or if a join is made it should take into account that the ManyToOne relationship is nullable and therefore do a LEFT OUTER JOIN.
Path.get(...) always defaults to an INNER JOIN. If you want a different join type, use Root.join(..., JoinType.LEFT), i. e. houseRoot.join(House_.garage, JoinType.LEFT).get(Garage_.id).
One solution that results in the same behaviour is:
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<House> query = cb.createQuery(House.class);
Root<House> houseRoot = query.from(House.class);
Path<Garage> garage = houseRoot.get(House_.garage);
Path<Long> garageId = garage.get(Garage_.id);
query.where(cb.or(cb.equal(garageId , 0), cb.isNull(garage)));
TypedQuery<House> typedQuery = entityManager.createQuery(query);
List<House> houses = typedQuery.getResultList();
This results in the following SQL:
SELECT H_ID, NAME, G_ID FROM HOUSE WHERE ((G_ID = 0) OR (G_ID IS NULL));
I have an Entity with OneToOne relation, which is used just to sort results:
#Entity
public class Document {
#Id
Long id;
#OneToOne()
SortProperty sortProp;
...
}
Then I have repository (using QueryDSL predicates):
public interface DocumentRepository
implements PagingAndSortingRepository<Document, Long>,
QueryDslPredicateExecutor<Document> {
#EntityGraph(value = "Document.forceJoins")
Page<Document> findAll(Predicate queryDslPredicate, Pageable pageable);
...
}
As you see above, I use #EntityGraph to control joining relations in the main query. All this work well, the only problem is performance - #OneToOne is fetched vith left outer join which means that DB index is not used:
select * from
document document0_
left outer join
sortproperty sortproper3_
on document0_.documentid=sortproper3_.documentid
...
Is there any way how to enforce using inner join instead of left outer join?
I have tried several things - #OneToOne(optional = false), #org.hibernate.annotations.Fetch, but no success ... Parts generated from QueryDSL predicate(s) use properly inner joins for the property, but the main part of query use always left outer join. I was trying also use annotation with this method:
#Query("select doc from Document doc inner join doc.sortProperties props")
but I was unable to use it properly together with paging and QueryDSL predicates.
Any idea?
Try this with #Query annotation.
#Query("select doc from Document doc join doc.sortProp props")
I use JPA 2.0 criteria builder. I need get data from one table and sort them by column from other. This tables have relations OneToMany:
class Club{
#OneToMany(mappedBy = "club")
private List<Address> addresses;
...
}
class Address{
#JoinColumn(name = "club_id", referencedColumnName = "id")
#ManyToOne(fetch = FetchType.LAZY)
private Club club;
#Column(name = "type")
private Long type;
#Column(name = "full_address")
private String full_address;
...
}
May be several address of some type but I need only one row of this specific address.
I write native queries with subquery, but it's has problem because subquery doesn't use in order clause and in select clause in JPA 2.0.
select c.full_name from club c
ORDER BY (select a.full_address from address a WHERE c.id= a.club_id and a.type=1 LIMIT 1)
select c.full_name, (select a.full_address from address a WHERE a.type=1 AND c.id=a.club_id LIMIT 1) as full_address FROM club c
ORDER BY fullAddress;
How I can replace native order by clause on JPA equivalent?
Thanks!
This native query also resolve problem and it can replace by JPA query
select c.full_name, min(a.full_address) FROM club c LEFT JOIN address a on c.id = a.club_id
where a.id is null or a.type=1 or not exists(SELECT 1 from address aSub WHERE aSub .club_id=c.id AND aSub.type=1)
GROUP BY c.id, c.full_name ORDER BY min(a.full_address);
JPA equivalent
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<ClubItem> query = builder.createQuery(ClubItem.class);
Root<Club> root = query.from(Club.class);
Join<Club, Address> addressJoin = root.join(Club_.address, JoinType.LEFT);
query.select(builder.construct(ClubItem.class, root.get(Club_.id), root.get(Club_.fullName), builder.function("min", String.class, addressJoin.get(Address_.fullAddress))));
Subquery<Address> subquery = query.subquery(Address.class);
Root<Address> addressRoot = subquery.from(Address.class);
subquery.select(addressRoot);
subquery.where(
builder.and(
builder.equal(addressRoot.get(Address_.type), 1),
builder.equal(addressRoot.get(Address_.clubId), root.get(Club_.id))));
query.where(builder.or(builder.isNull(addressJoin), builder.equal(addressJoin.get(Address_.type), builder.literal(new Long(1))),
builder.not(builder.exists(subquery))));
query.groupBy(root.get(Club_.id), root.get(Club_.fullName))
Order order = builder.asc(builder.function("min", String.class, addressJoin.get(Address_.fullAddress)));
query.orderBy(order);
TypedQuery<ClubItem> contentQuery = em.createQuery(query);
It's not terribly elegant, but it gets the job done...
Make your "Club" class implement Comparable. Put the order-by logic into the Comparable. Then use Collections.sort(unsortedList) to get the list into sorted form. There's also a Collections.sort(unsortedList, Comparable) method which could be useful, especially if you are doing a bunch of similar methods that just vary on order-by.
I have a problem in JPQL cascade query with eclipselink2.5
please see code
Entity code
public class Category{
...
#JoinColumn(name = "parent_category", referencedColumnName = "id")
#ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER,optional = true)
private Category parentCategory;
...
}
JPQL code
String jpql = "select o from Category o order by o.parentCategory.sort ASC";
problem
the problem is this JPQL return list does not include 'o' if 'o.parentCategory' is null.
please see this table http://i.stack.imgur.com/xsXvk.jpg
the return list only rows id is 2,3,4 .
because the column parent_category is null, I lost rows 1,5,6
the correct result should be return all rows
Looking forward to your help！
Using o.parentCategory.sort in the order by clause forces an inner join which filters nulls. If you want nulls included, you will need to use an explicit outer join in the query:
"select o from Category o outer join o.parentCategory parentCategory order by parentCategory.sort ASC"
I have two entities: parent Customer and child Order.
Each Customer has 1,000,000 Orders for example, so it is not needed in any given time to load a Customer with all Orders but I want to have this ability to make join query on these two entities in JPA.
So because of this, I must create #OneToMany relationship for making join queries.
My question is: how to get query without making joinColumn because even in Lazy mode it is possible to load 1,000,000 objects!
I just want to get query on these object with where restrictions like native join.
If you don't want the #OneToMany relationship implicitly set in your Customer class than you don't have to. You can execute JPQL queries (in very precise manner) without the marked relationship.
Assume you have:
#Entity
public class Customer {
// all Customer-related fields WITHOUT #OneToMany relationship with Order
}
#Entity
public class Order {
#ManyToOne
private Customer owner;
}
Then if you want to get all Orders for particular Customer you can execute a simple JPQL query like that:
// Customer customer = ...
// EntityManager em = ...
String jpql = "SELECT o FROM Order o WHERE o.owner = :customer";
TypedQuery<Order> query = em.createQuery(jpql, Order.class);
query.setParameter("customer", customer);
List<Order> orders = query.getResultList();
In this way you can execute the code only when you're really sure you want to fetch Customer's orders.
I hope I've understood your problem correctly.
EclipseLink has support for QueryKeys, that allow you to define fields or relationships for querying that are not mapped. Currently there in no annotation support for query keys, but you can define them using the API and a DescriptorCustomizer.
Also you do not need the OneToMany to query on it, just use the inverse ManyToOne to query,
i.e.
Select distinct c from Customer c, Order o where o.customer = c and o.item = :item
Or,
Select distinct o.customer from Order o join o.customer c where o.customer = c and o.item = :item