| From: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, David Rowley <dgrowleyml(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Andrew <pgsqlhackers(at)andrewrepp(dot)com> |
| Subject: | Re: pg_dump versus hash partitioning |
| Date: | 2023-03-11 03:32:32 |
| Message-ID: | 20230311033232.g6jgkuzxdawepsbe@jrouhaud |
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| Lists: | pgsql-hackers |
On Fri, Mar 10, 2023 at 10:10:14PM -0500, Tom Lane wrote:
> Julien Rouhaud <rjuju123(at)gmail(dot)com> writes:
> > Working on some side project that can cause dump of hash partitions to be
> > routed to a different partition, I realized that --load-via-partition-root can
> > indeed cause deadlock in such case without FK dependency or anything else.
>
> > The problem is that each worker will perform a TRUNCATE TABLE ONLY followed by
> > a copy of the original partition's data in a transaction, and that obviously
> > will lead to deadlock if the original and locked partition and the restored
> > partition are different.
>
> Oh, interesting. I wonder if we can rearrange things to avoid that.
The BEGIN + TRUNCATE is only there to avoid generating WAL records just in case
the wal_level is minimal. I don't remember if that optimization still exists,
but if yes we could avoid doing that if the server's wal_level is replica or
higher? That's not perfect but it would help in many cases.
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