[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3628) Hilo optimizer problem in case of multiple threads accessing the sequence table

[Tara Simpson (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=31878#action_31878 ] 

Tara Simpson commented on HHH-3628:
-----------------------------------

My original comment was a little narky, I apologise....but Steve's blog does recommend using the new generators.  "The new generators are available and highly recommended for use" is fairly Plain English.

Regarding the PooledOptimizer issue, see HHH-3608.

In meantime we've replaced all use of Hibernate's sequencers with our own working implementation - so for us the criticality of the issue is somewhat mitigated, but for many unsuspecting users it is not.  


> Hilo optimizer problem in case of multiple threads accessing the sequence table
> -------------------------------------------------------------------------------
>
>                 Key: HHH-3628
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3628
>             Project: Hibernate Core
>          Issue Type: Bug
>    Affects Versions: 3.2.6
>         Environment: Sybase
>            Reporter: Montagnon Cyril
>
> If 2 (or more) threads access the table storing the ids, this optimizer won't work and will try to insert entities with twice the same idea.
> The problem is the way the HiLoOptimizer class generates the id : 
>             public synchronized Serializable generate(AccessCallback callback) {
> 			if ( lastSourceValue < 0 ) {
> 				lastSourceValue = callback.getNextValue();
> 				while ( lastSourceValue <= 0 ) {
> 					lastSourceValue = callback.getNextValue();
> 				}
> 				hiValue = ( lastSourceValue * incrementSize ) + 1;
> 				value = hiValue - incrementSize;
> 			}
> 			else if ( value >= hiValue ) {
> 				lastSourceValue = callback.getNextValue();
> 				hiValue = ( lastSourceValue * incrementSize ) + 1;
> 			}
> 			return make( value++ );
> 		}
> In the 'else if' part, the 'value' variable isn't reaffected, which means the current thread will try to insert entities with an id that has already been used by another thread. The value should be reset with hiValue - incrementSize.

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