> -----Original Message-----
> From: pgsql-hackers-owner@postgresql.org
> [mailto:pgsql-hackers-owner@postgresql.org]On Behalf Of J. R. Nield
> Sent: Friday, August 02, 2002 5:12 PM
> To: Mikheev, Vadim
> Cc: Tom Lane; Richard Tucker; Bruce Momjian; PostgreSQL Hacker
> Subject: Re: [HACKERS] PITR, checkpoint, and local relations
>
>
> On Fri, 2002-08-02 at 16:59, Mikheev, Vadim wrote:
>
> > You don't need it.
> > As long as whole block is saved in log on first after
> > checkpoint (you made before backup) change to block.
>
> I thought half the point of PITR was to be able to turn off pre-image
> logging so you can trade potential recovery time for speed without fear
> of data-loss. Didn't we have this discussion before?
Suppose you can turn off/on PostgreSQL's atomic write on the fly. Which
means turning on or off whether XLoginsert writes a copy of the block into
the log file upon first modification after a checkpoint.
So ALTER SYSTEM BEGIN BACKUP would turn on atomic write and then checkpoint
the database.
So while the OS copy of the data files is going on the atomic write would be
enabled. So any read of a partial write would be fixed up by the usual crash
recovery mechanism.
>
> How is this any worse than a table scan?
>
> --
> J. R. Nield
> jrnield@usol.com
>
>
>
>
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