Re: CIC and deadlocks

On 3/31/07, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
>
> Hmm ... only if it's already set inVacuum true ... there's a window
> where it has not.
>
> I wonder whether we could change CIC so that the "reference
> snapshot" lists only transactions that are running and have already
> determined their serializable snapshot (ie, have set proc->xmin).
> Xacts that haven't yet done that can be ignored because they couldn't
> possibly see the dead tuples we're worried about, no?

Yes, it may work. Do we need to take some extra care because
proc-xmin is set while holding SHARED lock on proc array ?

Then we could rearrange the order of operations in vacuum_rel so
> that we lock the target rel before we acquire a snapshot. Then
> a vacuum waiting for the CIC cannot cause a deadlock.

We may need to do the same in analyze_rel.

Thanks,
Pavan

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