| From: | Greg Stark <stark(at)mit(dot)edu> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Freezing without write I/O |
| Date: | 2013-06-06 22:28:10 |
| Message-ID: | CAM-w4HMLcfJhiXzO3CLghyGpBwQxSxc91kr738j4Ab8eC-dZ6Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Jun 6, 2013 at 1:39 PM, Heikki Linnakangas
<hlinnakangas(at)vmware(dot)com> wrote:
> That will keep OldestXmin from advancing. Which will keep vacuum from
> advancing relfrozenxid/datfrozenxid. Which will first trigger the warnings
> about wrap-around, then stops new XIDs from being generated, and finally a
> forced shutdown.
>
> The forced shutdown will actually happen some time before going beyond 2
> billion XIDs. So it is not possible to have a long-lived transaction, older
> than 2 B XIDs, still live in the system. But let's imagine that you somehow
> bypass the safety mechanism:
Ah, so if you do the epoch in the page header thing or Robert's LSN
trick that I didn't follow then you'll need a new safety check against
this. Since relfrozenxid/datfrozenxid will no longer be necessary.
--
greg
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