Hibernate Warning HHH000444 using Oracle 10g with Wildfly 8.0.0 - follow-on Locking

Question

When making some queries in a view using JPA (2.1) with hibernate, I’m having this Warning. Though it’s working and it’s only one Warning, It bothers me a little bit.

WARN org.hibernate.Loader.Loader - HHH000444: Encountered request for Locking However dialect Reports that database prefers Locking be done in a Separate select (follow-on Locking); Results will be locked after initial query execute

This occurs in the following environment:

• JPA 2.1 / Hibernate 4.3.0.Final;
• Wildfly 8.0.0.Final;
• Oracle DB 10g;

Also, doing research on this Warning, I came up with a bug report for the Hibernate people who turned out to be rejected. In the bug, the problem also seems to occur in Oracle 11g.

How to correct or avoid this Warning?

Answer 1

The warning occurs because the lock in the same query by default is off. And it was disconnected for Oracle given limitations of the same in being able to select for update in several situations, mainly with queries involving paging (which in oracle 10 needs rownum + order by).

If you don’t lock into paginated queries, you can revert the behavior in the dialect. If you use, change your query to lock first in a separate query, or use Native query.

The standard Hibernate behavior in this case represents an error, because the lock a-posteriori of the second select represents a competition problem, because the record may have been changed between the two selects and the data used in the first will be different than expected

Answer 2

I don’t know if this can be considered a defect or not. But what happens is that in the dialect implemented by Hibernate for Oracle bases (org.hibernate.dialect.Oracle10gDialect), is returning true in the method informing the use of useFollowOnLocking. This ends up generating Warning. Don’t ask me what makes the followOnLocking, because I don’t know yet.

To suppress the problem, we need to create a class that extends the class org.hibernate.dialect.Oracle10gdialect and we must override the method public boolean useFollowOnLocking() to return false.

So the class would look like this:

import org.hibernate.dialect.Oracle10gDialect;

public class MeuDialetoOracle10g extends Oracle10gDialect {

    @Override
    public boolean useFollowOnLocking() {
        return false;
    }
}

After that, all you have to do is declare this dialect to be used in persistence.xml:

<property name="hibernate.dialect" value="br.com.meu.pacote.MeuDialetoOracle10g"/>

And that’s it. The Warning go away.