Hibernate Join two unrelated table when both has Composite Primary Key

Question

I'm writing java application using hibernate 5.2 but without HQL

there is two table, Transactions and ResponseCode

The logic of select statement which I want to be generated by Hibernate should look like this select bellow

SELECT t.tranType
      ,t.tranId
      ,t.requestDate
      ,t.rcCode
      ,t.tranAmount
      ,r.description
      ,r.status
  FROM transactions t
  LEFT OUTER JOIN responseCode r
    ON t.rcCode = r.rcCode
   AND (r.lang = 'en')
 WHERE (t.merchant_id =5 )

But something is wrong in my code, here is my implementation snippet

Transaction Entity

@Entity
@Table(name = "transactions")
public class Transaction implements java.io.Serializable {
    private static final long serialVersionUID = 1L;

        @Column(name = "merchant_id", nullable = true)
        private String merchantID;

        @Column(name = "tran_amount", nullable = true)
        private String tranAmount;

        @Id
        @Column(name = "tran_type", nullable = true)
        private String tranType;

        @Column(name = "auth_request_date", nullable = true)
        @Temporal(TemporalType.TIMESTAMP)
        private Date authRequestDate;

        @Id
        @Column(name = "tran_id", nullable = true)
        private String tranID;

        @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
        @JoinColumn(name="rc")
        private ResponseCode rc;

        // Contructos and getters/setters

ResponseCode Entity

@Entity
@Table(name = "response_codes")

public class ResponseCode implements java.io.Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "response_code")
    private String rcCode;

    @Column(name = "rc_status")
    private String rcStatus;

    @Column(name = "rc_description")
    private String rcDesc;

    @Column(name = "rc_lang")
    private String rcLang;
    // Contructos and getters/setters

Implementation code

CriteriaBuilder builder = session.getCriteriaBuilder();
CriteriaQuery<Transaction> criteria = builder.createQuery(Transaction.class);
Root<Transaction> transaction = criteria.from(Transaction.class);
Join<Transaction, ResponseCode> bJoin = transaction.join("rc",JoinType.LEFT);
bJoin.on(builder.equal(bJoin.get("rcLang"), tRequest.getLang()));

Predicate predicate = builder.and(transaction.get("merchantID").in(tRequest.getMerchantList()));
predicate = builder.and(predicate, builder.between(transaction.get("authRequestDate"), dateFrom, dateTo));
criteria.where(predicate);

Hibernate Generates two select statement, first statement gets transactions list, and second statement gets the response code details which is included in transactions list.

example: if there is 30000 transaction, and 15000 transaction has 000 response code, 5000 transaction has 116 response code and 10000 transaction has 400 response code, it will run second select statement three times, for 000,116 and 400 rcCode.

but the problem is that ResponseCode table contains several language for one response code

first select statement contains the restriction on language but second select statement does not has this restriction, and it does not meter which language is provided in first statement, the final result of transactions object contains for some transactions en language rc description and for some transactions ge language rc descriptions.

I think it depends on which language description was selected by oracle at last

Hibernate generated select I

SELECT t.tran_type
      ,t.tran_id
      ,t.auth_request_date
      ,t.merchant_id
      ,t.rc
      ,t.tran_amount
  FROM transactions t
  LEFT OUTER JOIN response_codes r
    ON t.rc = r.response_code
   AND (r.rc_lang = ?)
 WHERE (t.merchant_id IN (?))
   AND (t.AUTH_REQUEST_DATE BETWEEN ? AND ?)
 ORDER BY t.AUTH_REQUEST_DATE ASC

Hibernate generated select II

SELECT r.response_code  
      ,r.rc_description 
      ,r.rc_lang        
      ,r.rc_status      
  FROM response_codes r
 WHERE r.response_code = ? 
 //this select statement should have 'AND r.rc_lang = ?'

P.s If I make OneToMany relation it gets 30000 transaction and performs 30000 additional query to get response Code description for each operation, known as N + 1 problem

Do you know how to fix it?

Answer 1

Finally I found out that

Criteria API does not support joining unrelated entities. JPQL does not support that either. However, Hibernate supports it in HQL since 5.1. https://discourse.hibernate.org/t/join-two-table-when-both-has-composite-primary-key/1966

Maybe there is some workarounds, but in this case, I think the better way is to use HQL instead of Criteria API.

Here is HQL implementation code snippet (nothing was changed in entity classes)

String hql = "FROM Transaction t \r\n" + 
             " LEFT OUTER JOIN FETCH t.rc r \r\n" +
             " WHERE (t.merchantID IN (:merchant_id))\r\n" +
             " AND (t.authRequestDate BETWEEN :from AND :to)\r\n" +
             " AND (r.rcLang = :rcLang or r.rcLang is null)\r\n";

Query query =  session.createQuery(hql,Transaction.class);
query.setParameter("merchant_id", tRequest.getMerchantList());
query.setParameter("rcLang", tRequest.getLang());
query.setParameter("from", dateFrom);
query.setParameter("to", dateTo);

List<Transaction> dbTransaction = query.getResultList();

Answer 2

Change the relation from @OneToOne to @OneToMany and use fetch instead of join , it will execute only one query and hopefully it works.

 Join<Transaction, ResponseCode> join =
        (Join<Transaction,ResponseCode>)transaction.fetch("rc",JoinType.LEFT);

and you can try it with @OneToOne too.

Answer 3

Finally I found out that

Criteria API does not support joining unrelated entities. JPQL does not support that either. However, Hibernate supports it in HQL since 5.1. https://discourse.hibernate.org/t/join-two-table-when-both-has-composite-primary-key/1966

Maybe there is some workarounds, but in this case, I think the better way is to use HQL instead of Criteria API.

Here is HQL implementation code snippet (nothing was changed in entity classes)

String hql = "FROM Transaction t \r\n" + 
             " LEFT OUTER JOIN FETCH t.rc r \r\n" +
             " WHERE (t.merchantID IN (:merchant_id))\r\n" +
             " AND (t.authRequestDate BETWEEN :from AND :to)\r\n" +
             " AND (r.rcLang = :rcLang or r.rcLang is null)\r\n";

Query query =  session.createQuery(hql,Transaction.class);
query.setParameter("merchant_id", tRequest.getMerchantList());
query.setParameter("rcLang", tRequest.getLang());
query.setParameter("from", dateFrom);
query.setParameter("to", dateTo);

List<Transaction> dbTransaction = query.getResultList();