Comparing two collections of enums with Hibernate or SQL - mysql

Question

I have an entity 'Parent' which has a Set of enums
private Set<MyEnum> myEnums = EnumSet.noneOf(MyEnum.class);
#CollectionOfElements(targetElement=MyEnum.class)
#JoinTable
(name="PARENT_MY_ENUM",
joinColumns=#JoinColumn(name="PARENT_ID"))
#Enumerated(EnumType.STRING)
#Column (name="MY_ENUM", nullable=false)
public Set<MyEnum> getMyEnums(){
return myEnums;
}
public MyEnum {
ENUM_A,
ENUM_B,
ENUM_C,
ENUM_D;
}
Now I want to search for this entity with a collection of MyEnums. Only entities where all enums are set as in the search collection should be returned.
So if entity A has ENUM_A, ENUM_B and ENUM_C and entity B has ENUM_B, ENUM_C, ENUM_D a search with the search collectoin ENUM_A, ENUM_B, ENUM_C should only return entity A. A search for ENUM_B and ENUM_C should return nothing.
How would I do that in Hibernate?
if I do
select p from Parent p where p.myEnums IN (:searchCollection) and size(p.myEnums) = size(:searchCollection)
then this would return both entities for the first search.
Any ideas?
Update: I got a step further by figuring out how to do it in MySQL but applying this to Hibernate generates invalid SQL.
You would use a subquery with EXISTS for it like:
WHERE EXISTS(
SELECT pa.PARENT_ID, count(pme.MY_ENUM) FROM PARENT pa, PARENT_MY_ENUM pme
where pa.PARENT_ID = pme.PARENT_ID
AND pme.MY_ENUM IN ('ENUM_A','ENUM_B')
GROUP BY pa.PARENT_ID HAVING count(pme.MY_ENUM) = 2
)
But when I try to do the same in Hibernate:
select pa.ParentId, count(pa.myEnums) from Parent pa
WHERE pa.myEnums IN ('ENUM_A','ENUM_B')
GROUP BY pa.ParentId HAVING count(pa.myEnums) = 2
Hiberante creates this SQL statement:
select pa.CONTAINER_RELEASE_REFERENCE_ID as col_0_0_, count(.) as col_1_0_ from PARENT pa, PARENT_MY_ENUM enum1, PARENT_MY_ENUM enum2, PARENT_MY_ENUM enum3
where pa.PARENT_ID=enum1.PARENT_ID and pa.PARENT_ID=enum2.PARENT_ID and pa.PARENT_ID=enum3.PARENT_ID
and (. in ('ENUM_A' , 'ENUM_B'))
group by pa.PARENT_ID having count(.)=2
MySQL complains about the '.', Where is that coming from and why is Hibernate using 3 joins to PARENT_MY_ENUM?
Is this a Hibernate bug or what am I doing wrong?

Answer 1

Give the following a try for you exists subselect
select pa.ParentId, count(en) from Parent pa join pa.myEnums as en
WHERE en IN ('ENUM_A','ENUM_B')
GROUP BY pa.ParentId HAVING count(en) = 2
Otherwise, I wonder if something like that might not do the job
select p from Parent p join p.myEnums em
where (:results) = elements(em)
or
select p from Parent p join p.myEnums em
where (:results) in elements(em)

Answer 2

I think you can do that in java. Execute your initially proposed query, iterate the result and exclude (iterator.remove()) the false positives. It should be O(n), and I believe MySQL will require the same time to filter your result.