Re: PITR, checkpoint, and local relations

On Fri, 2002-08-02 at 16:01, Tom Lane wrote:
> "J. R. Nield" <jrnield@usol.com> writes:
> > The predicate for files we MUST (fuzzy) copy is: 
> >   File exists at start of backup && File exists at end of backup
> 
> Right, which seems to me to negate all these claims about needing a
> (horribly messy) way to read uncommitted system catalog entries, do
> blind reads, etc.  What's wrong with just exec'ing tar after having
> done a checkpoint?
> 
There is no need to read uncommitted system catalog entries. Just take a
snapshot of the directory to get the OID's. You don't care whether the
get deleted before you get to them, because the log will take care of
that. 

> (In particular, I *strongly* object to using the buffer manager at all
> for reading files for backup.  That's pretty much guaranteed to blow out
> buffer cache.  Use plain OS-level file reads.  An OS directory search
> will do fine for finding what you need to read, too.)

How do you get atomic block copies otherwise?

> 
>             regards, tom lane
> 
-- 
J. R. Nield
jrnield@usol.com