I have 2 linked tables in the same aggregate but Spring Data JDBC does not use join for retrieving data. It does several Select requests instead, and I don't see why.
The tables:
TestA (aggregate root)
idA (integer, PK)
TestB
idB (integer, PK)
idA (integer, FK -> TestA)
Entities:
@Data
public class TestA {
@Id
Integer idA;
@MappedCollection(idColumn = "idA")
Set<TestB> testBs = new HashSet<>();
}
@Data
public class TestB {
@Id
Integer idB;
}
Repository:
@Repository
public interface TestRepository extends CrudRepository<TestA, Integer> {
}
When calling testRepository.findAll(), it retrieves all the data and the objects are as expected (I have all the TestA with a list of associated TestB for each one), but it does it by requesting data from TestA, and then for each TestA line it requests TestB.
Executing prepared SQL statement [SELECT TestA.idA AS idA FROM TestA]
Executing prepared SQL statement [SELECT TestB.idB AS idB FROM TestB WHERE TestB.idA = ?]
Executing prepared SQL statement [SELECT TestB.idB AS idB FROM TestB WHERE TestB.idA = ?]
...
Why not a single Select with JOIN?? I guess I'm doing something wrong that is probably obvious, but I don't get it. For me and from my understanding it should be a left join or something like that, to retrieve in a single request data from TestA with the associated data from TestB.
