I make a query:
String query = "SELECT DISTINCT a FROM A a FETCH ALL PROPERTIES " +
"JOIN a.Bs AS b " +
"JOIN b.Cs AS c WHERE c = :c";
Query q = DAO.getSession().createQuery(query);
q.setParameter("c", c);
return q.list();
Even though I've said FETCH ALL PROPERTIES on a, when I access all the collections that A has, they still need to be loaded, thus aren't eagerly loaded. They have been defined as lazy loading, and that is the default behaviour I want, but this is the exception: I would like them loaded right now. I've tried swapping JOIN for LEFT OUTER JOIN to provoke Hibernate into loading them, and I've tried setting q.setFetchMode("a", FetchMode.EAGER), but it doesn't exist for Query.
The list of As is quite long, and they have quite a few collections, so making this an n+1 query thing is very slow (about ten seconds, as opposed to doing it in a single query which would be sub-second speed). I'd far prefer one query and loading all that's necessary in that one go. Any suggestions on how I can do that?
PS, Little bonus question: If I replace the "JOIN b.Cs AS c WHERE c = :c";
line with "WHERE :c IN b.Cs";, I get an SQL exception:
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '))' at line 1
The double paranthesis it's referring to is "and ('151000000-0000' in (.))" where 151000000-0000 is the primary key of c. Any idea why I get this error when I do it this way compared to not getting it when I do it the with joining b.Cs in?
UPDATE, as requested, here is the way I use for mapping. B and C are very similarly designed:
#Entity
#Table(name = "tblA")
public class A {
#Id
String AId;
#Column(name = "shortName", length = 12, nullable = false)
String shortName;
#OneToMany(fetch=FetchType.LAZY, mappedBy="theA")
private Set<B> Bs;
#OneToMany(fetch=FetchType.LAZY, mappedBy="theA")
private Set<D> Ds;
#OneToMany(fetch=FetchType.LAZY, mappedBy="theA")
private Set<E> Es;
#OneToMany(fetch=FetchType.LAZY, mappedBy="theA")
private Set<F> Fs;
}
theA in B, D, E and F is defined like this:
#ManyToOne(fetch=FetchType.LAZY)
#JoinColumn(name = "AId", nullable = true)
#ForeignKey(name="FK_KategoriID")
private A theA;
Cheers
Nik
fetch all properties is not what you want; it's used for telling Hibernate that you want it to fetch single-valued lazy-loaded properties. Details are here.
You need to specify join fetch in your query instead:
SELECT DISTINCT a FROM A a
LEFT JOIN FETCH a.Bs AS b
LEFT JOIN FETCH b.Cs AS c
WHERE c = :c
As far as bonus question goes, WHERE :c IN b.Cs is illegal syntax. Depending on how your C is mapped, you may want to look at elements() function instead.
FETCH ALL PROPERTIES only works for lazy properties (where a property is a String, Integer, ...) not one-to-may associations (i.e. collections)
see A Short Primer On Fetching Strategies
Related
I have a Join looking like:
Join<RepairEntity, RepairAssignEntity> joinRepairAssignEntities = root.join(RepairEntity_.repairAssignEntities, LEFT);
when it converted to SQL it looks like
left outer join
repair_assign repairassi1_
on repairenti0_.id=repairassi1_.repair_id
I want it to be like:
left outer join
repair_assign repairassi1_
on repairenti0_.PARENT_ID=repairassi1_.repair_id
If I add condition to that join:
Predicate equal = cb.equal(root.get(RepairEntity_.parentId), repairEntityPath.get(RepairEntity_.id));
joinRepairAssignEntities = joinRepairAssignEntities.on(equal);
it makes it
left outer join
repair_assign repairassi1_
on repairenti0_.id=repairassi1_.repair_id
and (
repairenti0_.parent_id=repairassi1_.repair_id
)
How do I get rid of
on repairenti0_.id=repairassi1_.repair_id
?
A priori it seems that the entities are not well related, if you want to join by the parent field it should be something like this:
Entity RepairEntity
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name="PARENT_ID")
RepairAssignEntity repairAssignEntity;
Entity RepairAssignEntity
#OneToMany(mappedBy="repairAssignEntity", fetch=FetchType.LAZY)
List<RepairEntity> RepairEntities;
if not, you would have to restructure the query to adapt it to the JPA entity modeling.
Regarding to get rid of the condition "on repairenti0_.id = repairassi1_.repair_id" you cannot because it is the implicit one of the relationship defined in the entity, but if you modify the modeling as I indicate, only the condition "repairenti0_.parent_id = repairassi1_ will appear. .repair_id "
I have 3 entities, infact many more joined together for brevity i'm skipping those and i'm using open jpa 2.2.2 and oracle 11g. Any thoughts what's going wrong here?
Entity SystemRules{
#OneToMany(mappedBy = "systemRule", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<ServiceActionMap> serviceActionMap;
}
Entity ServiceActionMap{
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "SYSTEM_RULE_ID")
private SystemRules systemRule;
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "RFS_TYPE_ID", nullable = true)
private RfsTypeMap rfsType;
}
Entity RfsTypeMap{
#Id
#Column(name="RFS_TYPE_ID" ,nullable=false)
private BigDecimal rfsTypeId;
#Column(name="RFS_NAME")
private String rfsName;
}
Now, I am trying to order the result by RfsTypeMap.rfsName, i'm creating query using criteria builder in following manner
CriteriaQuery<SystemRules> query = cb.createQuery(SystemRules.class);
Root<SystemRules> root= query.from(SystemRules.class);
root.fetch(SystemRules_.serviceActionMap).fetch(ServiceActionMap_.rfsType, JoinType.LEFT);
My order by clause is like this
cb.desc(cb.upper(systemRules.get("serviceActionMap").get("rfsType").get("rfsName").as(String.class)));
Generate JPQL looks like, where i expect a left outer join clause between ServiceActionMap and RfsTypeMap but it's missing. Same gets translated in SQL and i miss those records which are having ServiceActionMap.rfsType as null value.
SELECT DISTINCT s FROM SystemRules s INNER JOIN FETCH s.serviceActionMap INNER JOIN FETCH s.serviceActionMap INNER JOIN FETCH s.ruleProperty INNER JOIN FETCH s.ruleProperty where ... ORDER BY UPPER(s.serviceActionMap.rfsType.rfsName)
I tried going over several answers here but no success, tried explicitly putting a where clause for ServiceActionMap.rfsType is null as suggested on few answers but it's getting ignored, since join happens before where evaluation. Somewhere this question openJPA outer join on optional many-to-one when have order by clause matches my scenario but not able to generate suggested JPQL through criteria API.
I found one related bug on apache jira https://issues.apache.org/jira/browse/OPENJPA-2318. But, not sure that's the case.
I see that every join is repeated twice and even the join alias is always referring to SystemRules. It might be that orderby has caused the repeating inner joins and we may need to explicitly use Join object to refer to extended column.
CriteriaQuery<SystemRules> query = cb.createQuery(SystemRules.class);
Root<SystemRules> root = query.from(SystemRules.class);
Join<SystemRules, ServiceActionMap> join1 = root.join(SystemRules_.serviceActionMap, JoinType.INNER);
Join<ServiceActionMap, RfsTypeMap> join2 = join1.join(ServiceActionMap_.rfsType, JoinType.LEFT);
query.orderBy(cb.desc(cb.upper(join2.get(RfsTypeMap_.rfsName))));
I have the following 2 classes using JTA transaction type with openjpa & a derby embedded db. What I want is to get the parent Organisation & the requested WSpace in one query when I only have the WSpace id. I am quite new to JPA so am learning as I go and have been struggling with 'q2' query. I have been using queries 'q0' & 'q1' to debug and check the items do exist in the db. 'q0' returns 1 object as does 'q1', whereas 'q2' returns 0 objects
I have tried a variety of entity setups and different queries but nothing has worked yet.
Orignally the WSpace class did not have an Organisation field as it didn't seem necessary for persisting or selecting, but I added it (along with the mappedby parameter) incase it was needed for the query to work, but nothing has changed.
back to the original question how can I get this to work so it returns the parent object with the single child being requested
SELECT o FROM Organisation o JOIN FETCH o.spaces w WHERE w.id = :id
Here are my classes
#Entity
public class Organisation implements MyObjects
{
#Id
#NotNull
private Integer id;
private String name;
#OneToMany( mappedBy = "organisation",
cascade = { CascadeType.PERSIST, CascadeType.MERGE } )
private List<WSpace> spaces;
//getters/setter below
}
And
#Entity
public class WSpace implements MyObjects
{
#Id
#NotNull
private Integer id;
private String name;
#ManyToOne
private Organisation organisation;
#OneToMany
private List<Application> apps;
//getters/setter below
}
class DAO
{
...
public void foo( Integer id )
{
....
String q0 = "SELECT o FROM Organisation o WHERE o.id = 49068";
List<Organisation> res0 = em.createQuery( q0, Organisation.class ).getResultList();
String q1 = "SELECT w FROM WSpace w WHERE w.id = " + id;
List<WSpace> res1 = em.createQuery( q1, WSpace.class ).getResultList();
String q2 = "SELECT o FROM Organisation o "
+ "JOIN FETCH o.spaces w WHERE w.id = " + id;
List<Organisation> res2 = em.createQuery( q2, Organisation.class ).getResultList();
...
}
}
Have you tried to look in the logs for output of your q2 query?
I am learning JPA too and was dealing with Criteria and QL queries quite recently.
So after having pretty same problems with joins, I started checking logs and it was pretty clear, what the issues were, since logs showed up translated to SQL queries.
Another thing to look, how are you generating your Entities? I used Netbeans generating it for me. Also, many to many relations mignt have helper class generated too, I saw it in one of the projects.
Hope it helps..
The query you're looking for is probably this:
SELECT w FROM WSpace w LEFT JOIN FETCH w.organisation where w.id=:id
with query.setParameter("id", id); to bind the id parameter to the query. This effectively tells the persistence provider to fetch the WSpace.organisation relation while querying for WSpace entities in the same query. Using the LEFT [OUTER] keword (OUTER being optional) in front of the JOIN FETCH keywords tells your persistence provider to select WSpace objects even if there are no matching Organisation records for your WSpace.organisation relation.
I have the following relevant JPA annotated classes in a Spring-Boot JPA enabled project (All Groovy Code):
#Entity
abstract class Character {
#Id
String id;
String name;
#ElementCollection(targetClass = Episode)
#Enumerated(EnumType.ORDINAL)
Collection<Episode> appearsIn;
}
#Entity(name = "Human")
public class Human extends Character {
String homePlanet;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "favorite_droid_id")
Droid favoriteDroid;
}
public enum Episode {
PHANTOM_MENACE,
ATTACK_OF_THE_CLONES,
REVENGE_OF_THE_SITH,
A_NEW_HOPE,
EMPIRE_STRIKES_BACK,
RETURN_OF_THE_JEDI,
THE_FORCE_AWAKENS
}
When I attempt to execute the following JPA Query:
def query = em.createQuery("from Human h where h.appearsIn in (:episodes)");
query.setParameter("episodes", EnumSet.of(Episode.THE_FORCE_AWAKENS));
def result = query.getResultList();
The generated SQL statement does not seem to have the alias to the Character table or the column name for appears_in:
select human0_.id as id2_0_, human0_.name as name3_0_, human0_.favorite_droid_id as favorite6_0_, human0_.home_planet as home_pla5_0_
from character human0_
cross join character_appears_in appearsin1_
where human0_.dtype='Human' and human0_.id=appearsin1_.character_id and (. in (?))
I have also tried using equals instead of in, with the same behavior:
from Human h where h.appearsIn = :episode
Produces the following SQL:
select human0_.id as id2_0_, human0_.name as name3_0_, human0_.favorite_droid_id as favorite6_0_, human0_.home_planet as home_pla5_0_
from character human0_
cross join character_appears_in appearsin1_
where human0_.dtype='Human' and human0_.id=appearsin1_.character_id and .=?
Any help is greatly appreciated.
Your query is invalid - as #Neil Stockton pointed out, by writing h.appearsIn in (:episodes) you are saying "collection in collection" which does not make sense.
You should rather declare a "collection member variable" like this:
select distinct h
from Human h
join h.appearsIn ai
where ai in (:episodes)
ai represents a single element of appearsIn (like an iterator).
If you have this entity:
#Entity
public class A {
#ManyToOne
#JoinColumn(name = "bField", nullable = true)
private B myBObject;
}
And I have a generic generator of Criteria who will do that:
Root<A> root = criteria.from(A.class);
root.get("myBObject").get("aFieldInB");
The problem is the following: the generated sql will contains a CROSS JOIN between A and B.
But I would like that the generated sql will contains a LEFT JOIN between A and B.
How can I do that?
You must use a join(). In general it is better to always use a join() for relationships.
See,
http://en.wikibooks.org/wiki/Java_Persistence/Criteria#JoinType