Develop Reference

Querydsl ignores common table expression alias for JPA Entities

I need to build SQL query with common table expression using QueryDSL:
WITH cte AS (
SELECT DISTINCT BUSINESS_ID FROM BUSINESS WHERE MERCHANT_CODE like ?
)
SELECT t0.*
FROM PAYMENT t0
LEFT JOIN cte t1 ON t0.PAYER = t1.BUSINESS_ID
LEFT JOIN cte t2 ON t0.PAYEE = t2.BUSINESS_ID
WHERE (t1.BUSINESS_ID IS NOT NULL OR t2.BUSINESS_ID IS NOT NULL)
I have two JPA entities (Payment, Business).
This is how I implemented that:
String merchantCode = "abcd%";
QPayment payment = QPayment.payment;
QBusiness business = QBusiness.business;
QBusiness cte = new QBusiness("cte");
QBusiness merchant1 = new QBusiness("t1");
QBusiness merchant2 = new QBusiness("t2");
Configuration configuration = new Configuration(new OracleTemplates());
new JPASQLQuery<>(entityManager, configuration)
.with(cte,
JPAExpressions.selectDistinct(business.businessId).from(business)
.where(business.merchantCode.like(merchantCode)))
.select(payment)
.from(payment)
.leftJoin(cte, merchant1).on(payment.payer.eq(merchant1.businessId))
.leftJoin(cte, merchant2).on(payment.payee.eq(merchant2.businessId))
.where(merchant1.businessId.isNotNull()
.or(merchant2.businessId.isNotNull()));
And the problem is that during leftJoin it doesn't treat cte as a link, instead it inserts table name and two aliases: LEFT JOIN BUSINESS cte t1 ON .... I tried different templates – didn't help.
Am I doing something wrong or it's a QueryDSL bug?

JPQL doen't support CTEs, as we can see in grammar. And querydsl works over JPQL. CTEs are pretty vendor-specific, so you'll have to do one of following:
Rewrite query to be JPA-compatible
Use JPA native query
Query sql with querydsl (actually I don't remember if it supports CTEs)
From all above I would chose the 2nd option. Making native queries doen't harm your code. It makes your code more performant.

Take a good look at the tutorial
QCat cat = QCat.cat;
QCat mate = new QCat("mate");
QCat kitten = new QCat("kitten");
query.from(cat)
.innerJoin(cat.mate, mate)
.leftJoin(cat.kittens, kitten)
.list(cat);
You will want to .leftjoin(cte.merchant1, merchant1).on(...) or whatever the corresponding field is called in the parent "cte".
Basically you need to name the field which you want to join. Just stating the meta model does not suffice as there is no way of telling what you actually want. You can see it in your code (as well in the tutorial's kitten example): you have two Merchant you want to join to the cte, so which one is which.
The .on()-clause just states the conditions under which a join is valid, like you could place filters there.
.

JPA CriteriaQuery with ListJoin

I'm working with JPA CriteriaBuilder, CriteriaQuery etc. and static metamodels for typesafe queries, like here for example: click.
I have 3 tables: Client, Package, Vegetable.
Every client has 1 or more packages, and those packages contain multiple vegetables.
What I have now:
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<Client> query = builder.createQuery(Client.class);
Root<Client> root = query.from(Client.class);
ListJoin<Package, Vegetable> join = root.join(Client_.packages).join(Package_.vegetables);
TypedQuery<Client> typedQuery = entityManager.createQuery(query);
return typedQuery.getResultList();
The ListJoin I added recently. Point is what Hibernate does: generates the whole select for all fields in Client class from the Client table inner joined with Package and Vegetable, but it doesn't actually selects those fields from joined tables. It gets every package by ID and then every vegetable by ID, thus doing n+1 selects.
Without the ListJoin it doesn't inner join those tables, but I'm working on it right now so I added those joins. Now I want to select all the fields from those classes so I get whole object hierarchy with 1 select. I tried doing something with projections like in the link I gave in Projecting the result chaper, but I have no idea how to connect that with ListJoin.
Is that even possible in this situation? When I run this query on database (with manually added all the fields from joined tables) it works fine, but would Hibernate handle that? And if so - how to project the result so it selects all the fields from 3 tables joined together and constructs whole object hierarchy, all with 1 select?
//Edit: managed to retrieve all packages with a single query, but going further raises exception:
Root<Client> root = query.from(Root.class);
ListJoin<Client, Package> join = root.join(Client_.packages);
ListJoin<Package, Vegetable> secondJoin = join.join(Package_.vegetables);
root.fetch(Client_.packages);
Naturally, I tried to add: join.fetch(Package_.vegetables); but it raises the org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list, no idea what is that.
As to the latest comment: gonna try that now.
//Edit2: I added 2 fetches (couldn't cast them to Join like in that answer, compiler errors):
Fetch<Client, Package> join = root.fetch(Client_.packages);
Fetch<Package, Vegetable> secondJoin = join.fetch(Package_.vegetables);
It raises org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags, known error I guess so at least got something to search for.
//Edit3: Changed it both to Sets and it works, thanks, couldn't have done it without the Fetch instead of Join suggestion, seems kinda unintuitive to me.

Building ordered and limited delete request in jooq

I recently encountered the following problem with buiding queries in jooq (version 3.1.0):
I want to build delete statement with order and limit constraints. So, my aim is to build something like this:
DELETE FROM table ORDER BY field DESC LIMIT 1 (this is MySql syntax)
But i haven't found nesessary methods in result delete query object:
DSLContext context = createContext();
DeleteWhereStep delete = context.delete(createTable(table));
DeleteConditionStep whereStep = delete.where(condition);
whereStep.orderBy(...)//and no such method here
There are all nesessary methods in select statements and none for delete.
Is it possible to set order and limit for delete request in jooq?

As of jOOQ 3.2, these sorts of extensions are currently not implemented yet. Chances are, that #203 could be implemented in jOOQ 3.3, though.
In the mean time, you have two options:
Resort to plain SQL
i.e. write something like:
context.execute("DELETE FROM {0} ORDER BY {1} DESC LIMIT 1",
createTable(table),
field);
Manually transform your SQL statement into something equivalent
I suspect that the ORDER BY .. LIMIT extension to the MySQL DELETE statement is just sugar for:
DELETE FROM table t
WHERE t.id IN (
SELECT id FROM table
ORDER BY field LIMIT 1
)
Or with jOOQ:
context.delete(TABLE)
.where(TABLE.ID.in(
select(TABLE.ID)
.from(TABLE)
.orderBy(TABLE.FIELD)
.limit(1)
))

JPQL query containing LIKE converted into criteria

I need to use the LIKE operator into an JPA query. I need to use it for types other then String but the JPA criteria API allows me to add only String parameters. I tried using the .as(String.class) but something fails and also tried calling the CAST function from the underlying Oracle that again fails for unknown reasons to me.
I tried writing the query also in JPQL and it works as expected. This is the query:
SELECT p from CustomerOrder p where p.id like '%62%'
UPDATE:
The query must be built in a generic fashion as it is for filtering, so it needs to be created at runtime. On the query that is already created I tried to add the LIKE clause like this:
query.where(builder.like(selectAttributePath.as(String.class), "%"+filterValue.toString().toLowerCase()+"%"));
But this crashes with this exception:
org.hibernate.hql.internal.ast.QuerySyntaxException: expecting CLOSE, found '(' near line 1, column 156 [select distinct generatedAlias0.id from de.brueckner.mms.proddetailschedact.data.CustomerOrder as generatedAlias0 where cast(generatedAlias0.id as varchar2(255 char)) like :param0]
I executed the same query directly to Oracle using SQLDeveloper, so it should be sound from this point of view. So the problem is the Hibernate is the issue. Any suggestions on how to fix it?
How can I write this query using JPA Criteria?

I fixed the problem by invoking the 'TO_CHAR' function from the underlying Oracle DB and using the LIKE operator like for normal String's.
query.where(builder.like(selectAttributePath.as(String.class), "%" +filterValue.toString().toLowerCase() + "%")

You can try the below code, it might require modifications.
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<CustomerOrder> cq = cb.createQuery(CustomerOrder.class);
Root<CustomerOrder> order = cq.from(CustomerOrder.class);
cq.where(cb.like(Long.valueOf(order.get(CustomerOrder_.id)).toString(), "%62%"));
TypedQuery<CustomerOrder> q = em.createQuery(cq);
List<CustomerOrder> results = q.getResultList();

How to put 'null' into column using HQL?

How to build valid HQL string, which is equivalent to
UPDATE table SET field = null WHERE ....

Do you mean bulk HQL update? Try this
UPDATE myEntity e SET e.myProperty = null WHERE ...
You can also use a parameterized version of the above
UPDATE myEntity e SET e.myProperty = :param WHERE ...
In your code:
int updatedEntities = session.createQuery(updateQueryHQL)
.setString( "param", myValue ) // or .setString( "param", null )
.executeUpdate();
See documentation for details.
If you're not doing bulk updates, you should just set your property to NULL and persist the entity normally.

Why does your update statement need to be done in HQL? Do you have this table mapped to an entity in the system? If you do, then you can simply set the property that maps to that column to null, and run a save on that entity. eg.
myObject.setMyProperty(null);
getSessionFactory().getCurrentSession().save(myObject);
That should work for you, but you gotta have an entity mapped to the table in question.