Re: PG 8.3.3 - ERROR: lock AccessShareLock on object 16385/16467/0 is already held

Tom Lane wrote:
> [ reincluding the mailing list ]
>
> Michael Milligan <milli(at)acmeps(dot)com> writes:
> > Okay, it reproduces and surprise surprise nLocks does overflow...
>
> > ERROR: lock AccessShareLock on object 16385/16467/0 is already held
> > lock(0x87408a028) id(16385,16467,0,0,0,1) grantMask(a) waitMask(0)
> > req(2,0,1,0,0,0,0,0)=3 grant(1,0,1,0,0,0,0,0)=2 wait(0)
> > proclock(0x8743a7508) lock(0x87408a028) method(1) proc(0x8743aada8) hold(a)
> > locallock(0xb29c78) nLocks(-2147483648) nOwners(2) mOwners(8)
>
> Hah. Okay, that shows that we'd never have reproduced it with a small
> test case.
>
> > So I'm guessing this is not a bug? Just that for some reason 8.3.3 is
> > grabbing more locks than 8.2.6 does and I have to adjust my batch
> > processes to break things up into chunks of less than 10 million per
> > transaction... :-/
>
> Well, I'm wondering exactly why 8.3 is taking more locks than 8.2 does,
> because AFAICS it shouldn't. Could you extract a complete example of
> what your code does per tuple? I would like to run a small test case
> and just see where the LockAcquire calls come from in each version.
> (Or, if you prefer, you can get out gdb and do the legwork yourself...)
> It's true that breaking up the transaction is likely to be the best
> short-term answer for you, but I think there might be a bug here.
>
> In any case, now that we know that nLocks overflow is actually possible
> within real-world transaction lengths, it'd behoove us to do something
> about that in 8.4 or beyond.

Is this a TODO?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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