Mulitple updates in a transaction; newbie question

SnapShot · **Joined:** Sat May 13, 2006 12:00 pm **Posts:** 19

Hibernate version:3.2.0.ga

Code between sessionFactory.openSession() and session.close():

see below...

Name and version of the database you are using:

MySQL 4.1.13

The question may be related to this but I'm not sure. Problems with Session and transaction handling?
Read this: http://hibernate.org/42.html I'm using Hibernate in tomcat with the JDBC transaction handling as described in the document above...

Question: Is it possible to have multple "updates" where each update uses the initial data values in a table?

I'm trying to implement a tree as a "nested set" and I'm trying to implement a move node function.

The data set might look like this:

Code:

A 2 [127,150] (11 children)
 . B(2,0) [128,129] (0 children)
 . B(2,1) [130,131] (0 children)
 . B(2,2) [132,133] (0 children)
 . B(2,3) [134,135] (0 children)
 . B(2,4) [136,137] (0 children)
 . A 3 [138,149] (5 children)
 . . B(3,0) [139,140] (0 children)
 . . B(3,1) [141,142] (0 children)
 . . B(3,2) [143,144] (0 children)
 . . B(3,3) [145,146] (0 children)
 . . B(3,4) [147,148] (0 children)

Where the numbers in brackets represent the left and right extents of the tree nodes.

I want to move node "A 3" before node B(2,0) so I have three updates in the method like this...

Code:

Session session = sessionFactory.getCurrentSession();
Transaction tx = session.beginTransaction();
         
         

StringBuilder moveLeftUpdate = new StringBuilder();
moveLeftUpdate.append("update ")
        .append(name)
        .append(" set right_extent = right_extent - :offset, left_extent = left_extent - :offset ")
        .append(" where left_extent >= :thisLeft and right_extent <= :thisRight");
int moveLeftResult = session.createQuery( moveLeftUpdate.toString())
        .setInteger("offset", offset)
        .setInteger("thisLeft", left)
        .setInteger("thisRight", right)
        .executeUpdate();
LOG.info("MOVE LEFT RESULTS :: "+ moveLeftResult);

StringBuilder moveRightUpdate = new StringBuilder();
moveRightUpdate.append("update ")
        .append(name)
        .append(" set right_extent = right_extent + :offset, left_extent = left_extent + :offset ")
        .append(" where left_extent >= :referenceLeft and right_extent <= :referenceRight");
int moveRightResult = session.createQuery( moveRightUpdate.toString())
        .setInteger("offset", offset)
        .setInteger("referenceLeft", referenceLeft)
        .setInteger("referenceRight", referenceRight)
        .executeUpdate();
LOG.info("MOVE RIGHT RESULTS :: "+ moveRightResult);

if(rangeDifference != 0 && (left - referenceRight > 1)) {
    
    StringBuilder shiftInteriorUpdate = new StringBuilder();
    shiftInteriorUpdate.append("update ")
            .append(name)
            .append(" set right_extent = right_extent + :range, left_extent = left_extent + :range ")
            .append(" where left_extent > :referenceRight and right_extent < :thisLeft");
    int interiorShiftResult = session.createQuery( shiftInteriorUpdate.toString())
            .setInteger("range", rangeDifference)
            .setInteger("referenceRight", referenceRight)
            .setInteger("thisLeft", left)
            .executeUpdate();
    LOG.info("SHIFT INTERIOR RESULTS :: "+ interiorShiftResult);
}

tx.commit();

With this code in the example the log prints out:

Code:

MOVE LEFT RESULTS :: 6
MOVE RIGHT RESULTS :: 1
SHIFT INTERIOR RESULTS :: 7

In other words, the updated value from the first update are within the range of the last update and get updated twice.

I thought transactions where suppposed to prevent this, but either: A. I'm not using transactions correctly, B. don't have them set up correctly, or C. transactions are not the proper way of dealing with this.

Can anyone tell me which option I'm experiencing?

narenderreddy · **Joined:** Tue Dec 12, 2006 7:52 am **Posts:** 20

hi
why u use every time session.openSession(); the best way is you write one class i.e., HibernateUtil class in that class you write the code for opening the session and closing the session and you writhe the code of getting the connection like this
HibernateUtil.getInstanca.currentSession();
this is the best way and you over come that session problem you have any idea on HibernateUtil class is ok if you dont have any idea u search that HibernateUtil.java in google before the transaction commited you you update the data base values by using session.update(obj) once

evdelst · **Joined:** Wed Aug 24, 2005 11:49 am **Posts:** 63

It's C

:-)

You can modify entities returned from a query or session.load/get
Then, you can modify the properties of the entities. During the transaction commit, all changes will performed in one go.

If you perform a query after modifying a property, Hibernate can decide to perform the update (=flush) before transaction commit (so the query will return the correct data within this transaction).
So the second query uses the changed values. The transaction only makes sure:
- other sessions don't see the data before commit. Within the same transaction, you see changed data immediately (I think this is what confuses you)
- you can rollback or commit ALL the changes in one atomic operation.