| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: should there be a hard-limit on the number of transactions pending undo? |
| Date: | 2019-07-19 18:57:25 |
| Message-ID: | CAH2-WzkB_ygO1bUAW6wpgCCi79n3xZZus7vXTdFE9SBaCT7idA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Jul 19, 2019 at 10:28 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> In scenario #2, the undo work is going to have to be retried in the
> background, and perforce that means reacquiring locks that have been
> released, and so there is a chance of long lock waits and/or deadlock
> that cannot really be avoided.
I haven't studied the UNDO or zheap stuff in any detail, but I am
concerned about rollbacks that deadlock. I'd feel a lot better about
it if forward progress was guaranteed, somehow. That seems to imply
that locks are retained, which is probably massively inconvenient to
ensure. Not least because it probably requires cooperation from
underlying access methods.
--
Peter Geoghegan
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