We Keep Coding

Hibernate query with subquery in WHERE clause and multiple joins

I have been trying to get Hibernate to generate me a query with a subquery in its where clause. I've used this answer as a base to help me going, but this question mentioned only one table.
However, this is what I would need (in SQL):
SELECT [...]
FROM a
LEFT OUTER JOIN b on a.idb = b.idb
LEFT OUTER JOIN c on b.idc = c.idc
[...]
LEFT OUTER JOIN k out on j.idk = k.idk
WHERE k.date = (SELECT max(date) from k in where in.idk = out.idk) OR k.date is null
As I am not very used to using Hibernate, I'm having trouble specifying these inner joins while navigating in the inner constraints.
I was able to re-create the initial criteria as in the linked answer, but I can't seem to join the criteria and the rootCriteria.

If the entities are properly joined with #ManyToOne annotations, simply joining the criteria to the previous table will be enough to propagate the criteria to the whole query.
The following code seems to work properly to add the WHERE clause I'm looking for.
DetachedCriteria kSubquery = DetachedCriteria.forClass(TableJPE.class,"j2");
kSubQuery = kSubQuery.createAlias("k","k2");
kSubQuery.setProjection(Projections.max("k2.date"));
kSubQuery = kSubQuery.add(Restrictions.eqProperty("j.id", "j2.id"));
rootCriteria.add(Restrictions.disjunction()
.add(Subqueries.propertyEq("k.date",kSubQuery))
.add(Restrictions.isNull("k.date")));

How do I set a Restriction in Hibernate to target a column in either one of two joined tables?

I'm joining one table to another. The join works. I want to restrict the results to records with an "Error" message that can be in either table. When I do the following, I get no results back, yet I know there should be 2.
Criteria criteria = session.createCriteria(TableName.class);
criteria.createAlias("someList", "things");
Criterion restriction1 = Restrictions.eq("status", "Error");
Criterion restriction2 = Restrictions.eq("things.anotherStatus", "Error");
criteria.add(Restrictions.or(restriction1, restriction2));
finalList = criteria.list();
I noticed that the restrictions by themselves actually work. So, if I only do the first restriction on the original table with no alias OR if I only do the second restriction on the alias table, then I get 1 result each time.
Also, a simple join SQL query like the one below works as expected:
Select count(*)
From table1 t1
Left join table2 t2 on t1.id = t2.another_id
Where t1.status = 'ERROR' or t2.anotherStatus = 'ERROR'
How can I get this right in Hibernate?
EDIT 1: I now see that Hibernate does an Inner Join when I use the #JoinColumn annotation. How can I change it to do an Outer Join instead?
EDIT 2: Even adding #Fetch(FetchMode.JOIN) still results in an inner join! What gives? The documentation clearly says it will do an outer join. The annotation now looks like this:
#OneToMany
#JoinColumn(name="ID_FK")
#Fetch(FetchMode.JOIN)
private List<Thing> things;

Answer: use criteria.createAlias("someList", "things", JoinType.LEFT_OUTER_JOIN); instead.
Explanation: When no JoinType is specified, createAlias does an inner join by default.

Eclipselink group by is not working

How to add groupBy criteria to the code below? Because if I add criteriaQuery.groupBy(from.get(minutis.Preke_.prId)); - I get exactly the same SQL statement (without groupBy):
CriteriaBuilder cb = MinutisManager.getInstance().getCriteriaBuilder();
CriteriaQuery criteriaQuery = cb.createQuery(minutis.Preke.class);
Root<minutis.Preke> from = criteriaQuery.from(minutis.Preke.class);
from.fetch(minutis.Preke_.tiekejai, JoinType.LEFT).fetch(minutis.PrekeTiekejas_.tiekejas, JoinType.LEFT);
//criteriaQuery.groupBy(from.get(minutis.Preke_.prId));
TypedQuery<minutis.Preke> typedQuery = MinutisManager.getInstance().createQuery(criteriaQuery);
typedQuery.setFirstResult(0);
typedQuery.setMaxResults(100);
typedQuery.getResultList();
EDIT 1:
criteriaQuery.distinct(true) is not an option for me. Because that command hangs the whole statement and if I use EXPLAIN:
If I use GROUP BY on the query, then EXPLAIN is:
EDIT 2:
I get this SQL statement with and without criteriaQuery.groupBy(from.get(minutis.Preke_.prId));
SELECT ... FROM preke t1 LEFT OUTER JOIN preke_tiekejas t0 ON (t0.pr_id = t1.pr_id) LEFT OUTER JOIN tiekejas t2 ON (t2.tiek_id = t0.tiek_id) LEFT OUTER JOIN gamintojas t3 ON (t3.gam_id = t1.gam_id) LEFT OUTER JOIN google_compare t4 ON (t4.pr_id = t1.pr_id) LEFT OUTER JOIN grupe t5 ON (t5.pgs_id = t1.pgs_id) LEFT OUTER JOIN preke_kaina t6 ON (t6.pr_id = t1.pr_id) ORDER BY t1.pr_id LIMIT ?, ?

The SQL for the GROUP BY query should definitely contain a GROUP BY. Ensure that you are compiling and deploying the code correctly.
It could be a bug that the group by is ignored, as normal group by queries will not select object, but aggregated values. Check that you are using the latest release, and perhaps log a bug, or try JPQL.
In general your query does not make any sense, normally on a group by query you can only select the fields that you grouped by, or aggregation functions.
Perhaps consider batch fetching instead of join fetching.
http://java-persistence-performance.blogspot.com/2010/08/batch-fetching-optimizing-object-graph.html

I will file a bug in Eclipselink, because if I change fetch line with QueryHints, everything works:
Change this (with this line I get duplicate Preke entities with populated children entities):
from.fetch(minutis.Preke_.tiekejai, JoinType.LEFT).fetch(minutis.PrekeTiekejas_.tiekejas, JoinType.LEFT);
To this (with this lines I get unique Preke entities with populated children entities):
typedQuery.setHint(QueryHints.LEFT_FETCH, "Preke.tiekejai");
typedQuery.setHint(QueryHints.LEFT_FETCH, "Preke.tiekejai.tiekejas");
I get my desired result.
EDIT 1:
The bug really exists, now max resulsts is not working. Both cases typedQuery is identical.
typedQuery.setMaxResults(100);
System.out.println(typedQuery.getResultList().size()); //prints 73
typedQuery.setMaxResults(500);
System.out.println(typedQuery.getResultList().size()); //prints 413

No problem, I found the bug report, here it is, just in case someone else needs it.Criteria api ignores group by statement

Projections.countDistinct with Hibernate produces unexpected result

I have the following code
Criteria criteria = this.getCriteriaForClass(DeviceListItem.class);
Projection rowCountProjection = Projections.countDistinct("color");
criteria.setProjection(rowCountProjection);
int rowCount = ((Long) criteria.uniqueResult()).intValue();
return rowCount;
, whose purpose is to find out the number of rows with different values for the field named "color". The problem is that
Projections.countDistinct("color");
returns the same number of results as
Projections.count("color");
even though there are multiple rows with same color in the database view. When converting the Criteria object to SQL, I see that the SQL produced by Hibernate is
select count(this_.COLOR) as y0_ from DEVICESLIST_VIEW this_ where 1=1
when I would expect it to be
select count(distinct this_.COLOR) as y0_ from DEVICESLIST_VIEW this_ where 1=1
Why doesn't it work like expected and is there some remedy? Unfortunately I have no option to use HQL in this case.

It's a bug, fixed in 3.5.2: HHH-4957.

JPA and aggregate functions. How do I use the result of the query?

I'm new to ORM stuff and I need some help understanding something.
Let's assume I have the following standard SQL query:
SELECT *, COUNT(test.testId) AS noTests FROM inspection
LEFT JOIN test ON inspection.inspId = test.inspId
GROUP BY inspection.inspId
which I want to use in JPA.
I have an Inspection entity with a one-to-many relationship to a Test entity. (an inspection has many tests)
I tried writing this in JPQL:
Query query = em.createQuery("SELECT insp, COUNT(???what???) " +
"FROM Inspection insp LEFT JOIN insp.testList " +
"GROUP BY insp.inspId");
1) How do I write the COUNT clause? I'd have to apply count to elements from the test table but testList is a collection, so I can't do smth like COUNT(insp.testList.testId)
2) Assuming 1 is resolved, what type of object will be returned. It will definitely not be an Inspection object... How do I use the result?

You can give an alias to the joined entity (with AS)
You can create either a new object, or a List with the returned values
So:
SELECT new com.yourproject.ResultHolder(insp, COUNT(test.testId))
FROM Inspection insp LEFT JOIN insp.testList AS test GROUP BY insp.inspId
Or
SELECT new list(insp, COUNT(test.testId))
FROM Inspection insp LEFT JOIN insp.testList AS test GROUP BY insp.inspId
The result is then accessible either as an instance of ResultHolder, or as a java.util.List, where the insp is list.get(0), and the count is list.get(1)