Problem: HQL query is not returning any results when I reference an entities collection field as part of the HQL statement. It works for one HQL projection for example like this:
select inc.categoryTypes as categoryTypes from IncidentEntity inc where (inc.id = :id105019)
The categoryTypes is one of the IncidentEntity classes fields (which is a collection defined as a ManyToMany join as seen below). This works fine, but the issue arises when I am attempting to reference another projection collection that is mapped as a ManyToMany join.
select inc.categoryTypes as categoryTypes, inc.consequences as consequences from IncidentEntity inc where (inc.id = :id105019)
As soon as I do it like this, I get an empty set. Which means the SQL query that hibernate generates isn't returning anything. I have verified this by executing the command within SQL Manager which returns no results.
Here is the IncidentEntity:
/**
* Database entity for the 'incidents' table records.<br>
* Entity domain object is {@link nz.co.doltech.ims.shared.domains.Incident}
* @author Ben Dol
*
*/
@javax.persistence.Entity(name = "incidents")
@Cache(usage=CacheConcurrencyStrategy.TRANSACTIONAL)
public class IncidentEntity implements Entity {
...
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "incident_categorytype", joinColumns = {
@JoinColumn(name = "incident_id") },
inverseJoinColumns = {
@JoinColumn(name = "categorytype_id")
})
private Set<CategoryTypeEntity> categoryTypes = new HashSet<CategoryTypeEntity>();
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "incident_consequence", joinColumns = {
@JoinColumn(name = "incident_id") },
inverseJoinColumns = {
@JoinColumn(name = "consequence_id")
})
private Set<ConsequenceEntity> consequences = new HashSet<ConsequenceEntity>();
...
public Set<CategoryTypeEntity> getCategoryTypes() {
return categoryTypes;
}
public void setCategoryTypes(Set<CategoryTypeEntity> categoryTypes) {
this.categoryTypes = categoryTypes;
}
public Set<ConsequenceEntity> getConsequences() {
return consequences;
}
public void setConsequences(Set<ConsequenceEntity> consequences) {
this.consequences = consequences;
}
...
}
CategoryTypeEntity relationship definition:
@ManyToMany(fetch = FetchType.LAZY, mappedBy = "categoryTypes")
private Set<IncidentEntity> incidents = new HashSet<IncidentEntity>();
ConsequenceEntity relationship definition:
@ManyToMany(fetch = FetchType.LAZY, mappedBy = "consequences")
private Set<IncidentEntity> incidents = new HashSet<IncidentEntity>();
Data structure:
Using Hibernate 3.6.10
Maybe I have setup the definitions wrong, or I am missing a limitation with the HQL here, I'm not sure. Would appreciate any help that I could get here. Thanks!
Regards, Ben
You know that you are generating a Cartesian product with this query, right?
The query can be better visualized as:
select categoryTypes, consequences
from IncidentEntity inc
inner join inc.categoryTypes as categoryTypes
inner join inc.consequences as consequences
where (inc.id = :id105019)
Because you haven't specify an explicit join, an INNER JOIN is assumed not a LEFT JOIN.
Let's assume there are categories for the specified incident. So this query will return the categories for this incident, which is what you also reported:
select categoryTypes
from IncidentEntity inc
inner join inc.categoryTypes as categoryTypes
where (inc.id = :id105019)
But when there are no consequences, the INNER JOIN will return no result, so:
select categoryTypes, consequences
from IncidentEntity inc
inner join inc.consequences as consequences
where (inc.id = :id105019)
will not return anything, but then this can happen for your query too:
select categoryTypes, consequences
from IncidentEntity inc
inner join inc.categoryTypes as categoryTypes
inner join inc.consequences as consequences
where (inc.id = :id105019)
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