[hibernate-dev] [ORM] Synchronization on AbstractLoadPlanBasedLoader

[Vlad Mihalcea]

Hi,

We really need to test it thoroughly because the current pooled optimizer
are reasonably fast especially when used with a database sequence.
The table generators are slow because of the row-level locking, so I won't
include those in this discussion.

What strikes me is the synchronized block which might cause contention we
didn't have before.
I'd also vote for a new optimizer instead of modifying the pooled or the
pooled-lo ones.
The current optimizer are quite easy to grasp, and, if we are to add a
high-performance one, I think a new implementation is better suited for
this task.

Vlad

On Mon, Dec 14, 2015 at 6:25 PM, Sanne Grinovero <sanne at hibernate.org>
wrote:

> Hi all,
> while reviewing an improvement by Stale about reducing
> synchronization, I'm having the impression that the synchronization
> could be completely removed.
>
> But there's a comment warning me against that, so for sake of safety
> I'm merging the improvement without risking going too far:
>
>  // synchronized to avoid multi-thread access issues; defined as
> method synch to avoid
>  // potential deadlock issues due to nature of code.
>
> I tried to figure what "potential deadlock" it's referring to, but I'm
> having the impression the comment might be outdated. So I've reduced
> the contention to the only include the code block about which I'm not
> confident.
> By looking into git history, it seems the comment isn't related to any
> specific fix but was included already when this class was first
> created.
>
> Would someone be able to point out what is the issue this is protecting
> against?
>
> That should allow us to provide an even better patch, although I'll
> apply the safe one for now so to at least have the benefits already
> when wrapping of result-sets is disabled.
>
> thanks,
> Sanne
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