| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Florian Pflug <fgp(at)phlo(dot)org> |
| Cc: | Ants Aasma <ants(at)cybertec(dot)at>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)2ndquadrant(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Enabling Checksums |
| Date: | 2013-04-17 16:42:51 |
| Message-ID: | 20130417164251.GN5343@momjian.us |
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| Lists: | pgsql-hackers |
On Wed, Apr 17, 2013 at 06:33:58PM +0200, Florian Pflug wrote:
> > I was going to ask about the flexibility of pg_upgrade and checksums.
> > Right now you have to match the old and new cluster checksum modes, but
> > it seems it would be possible to allow pg_upgrade use from checksum to
> > no-checksum servers. Does the backend look at the pg_controldata setting,
> > or at the page checksum flag? If the former, it seems pg_upgrade could
> > run a a no-checksum server just fine that had checksum information on
> > its pages. This might give us more flexibility in changing the checksum
> > algorithm in the future, i.e. you only lose checksum ability.
>
> AFAIK, there's currently no per-page checksum flag. Still, being only
> able to go from checksummed to not-checksummed probably is for all
> practical purposes the same as not being able to pg_upgrade at all.
> Otherwise, why would people have enabled checksums in the first place?
Good point, but it is _an_ option, at least.
I would like to know the answer of how an upgrade from checksum to
no-checksum would behave so I can modify pg_upgrade to allow it.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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