| From: | andres(at)anarazel(dot)de (Andres Freund) |
|---|---|
| To: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Freeze avoidance of very large table. |
| Date: | 2015-12-17 07:26:26 |
| Message-ID: | 20151217072626.GK23112@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2015-12-17 16:22:24 +0900, Michael Paquier wrote:
> On Thu, Dec 17, 2015 at 4:10 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2015-12-17 15:56:35 +0900, Michael Paquier wrote:
> >> On Thu, Dec 17, 2015 at 3:44 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> >> > For me, rewriting the visibility map is a new data loss bug waiting to
> >> > happen. I am worried that the group is not taking seriously the potential
> >> > for catastrophe here.
> >>
> >> FWIW, I'm following this line and merging the vm file into a single
> >> unit looks like a ticking bomb.
> >
> > And what are those risks?
>
> Incorrect vm file rewrite after a pg_upgrade run.
If we can't manage to rewrite a file, replacing a binary b1 with a b10,
then we shouldn't be working on a database. And if we screw up, recovery
i is an rm *_vm away. I can't imagine that this is going to be the
actually complicated part of this feature.
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