Re: timeout on lock feature

I can imagine some people wanting this. However, 7.1 has new deadlock
detection code, so I would you make a 7.1 version and send it over. We
can get it into 7.2. I think we need a SET variable, and it should
default to OFF.

Good idea. Thanks.

> Hi,
>
> I implement additional server functionality. Currently (v7.0.3), executing
> SQL update statement on the same
> row from inside two different processess results in blocking second process
> to the end of transaction in
> the first one. In real OLTP application second process can't wait too long.
> After few seconds server should
> return to the application message:'lock timeout exceeded'. I modify postgres
> lock manager source code to
> obtain that functionality. I take advantage of deadlock detection mechanism.
> Currently deadlock
> detection routine initialy check for simple deadlock detection between two
> processess, next insert lock
> into lock queue and after DEADLOCK_CHECK_TIMER seconds run HandleDeadLock to
> comprehensive deadlock detection.
> To obtain 'timeout on lock' feature I do as follow:
>
> 1. Add new configure parameter. Currently I add #define statement in file
> include/config.in
> #define NO_WAIT_FOR_LOCK 1
> In the future somebody can add new option to SQL SET command
>
> 2. Modify HandleDeadLock routine. In file backend/storage/lmgr/proc.c change
> lines 866-870
>
> if (!DeadLockCheck(MyProc, MyProc->waitLock))
> {
> UnlockLockTable();
> return;
> }
>
> to
>
> if (!NO_WAIT_FOR_LOCK)
> {
> if (!DeadLockCheck(MyProc, MyProc->waitLock))
> {
> UnlockLockTable();
> return;
> }
> }
>
> With this modyfication every conflicting lock wait DEADLOCK_CHECK_TIMER
> seconds in queue and returns with error
> 'deadlock detect'.
>
> Who can add this simply 'timeout on lock' implementation to the next
> postgres server release?
>
>
>
>
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