Re: XID-wraparound hazards in LISTEN/NOTIFY

On Sat, Nov 23, 2019 at 12:10:56PM -0500, Tom Lane wrote:
> Mark Dilger <hornschnorter(at)gmail(dot)com> writes:
> > On 11/23/19 8:34 AM, Tom Lane wrote:
> >> It suddenly strikes me to worry that we have an XID wraparound hazard
> >> for entries in the notify queue.
>
> > Is it worth checking for this condition in autovacuum?
>
> Dunno, maybe. It's a different avenue to consider, at least.
>
> > There shouldn't be too much reason to back-patch any of this, since
> > the change in 51004c717 only applies to v13 and onward. Or do you
> > see the risk you described as "pretty minimal" as still being large
> > enough to outweigh the risk of anything we might back-patch?
>
> There may not be a risk large enough to worry about before 51004c717,
> assuming that we discount cases like a single session staying
> idle-in-transaction for long enough for the XID counter to wrap
> (which'd cause problems for more than just LISTEN/NOTIFY). I haven't
> analyzed this carefully enough to be sure. We'd have to consider
> that, as well as the complexity of whatever fix we choose for HEAD,
> while deciding if we need a back-patch.

Is this still an open issue? Should it be a TODO item?

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Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

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