Re: pg_migrator progress

Robert Treat wrote:
> On Wednesday 18 February 2009 10:47:25 Tom Lane wrote:
> > Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> > > Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> > >> No, but this would just be the same situation that prevails after
> > >> OID-counter wraparound, so I don't see a compelling need for us to
> > >> change the OID counter in the new DB. If the user has done the Proper
> > >> Things (ie, made unique indexes on his OIDs) then it won't matter.
> > >> If he didn't, his old DB was a time bomb anyway.
> > >
> > > Also I wonder about the performance of skipping over thousands or even
> > > millions of OIDs for something like a toast table.
> >
> > I think that argument is a red herring. In the first place, it's
> > unlikely that there'd be a huge run of consecutive OIDs *in the same
> > table*. In the second place, if he does have such runs, the claim that
> > he can't possibly have dealt with OID wraparound before seems pretty
> > untenable --- he's obviously been eating lots of OIDs.
> >
>
> Yeah, but its not just lots... it's lots and lots of lots. Sure, I have
> multi-billion row _tables_ now, but I know I ran systems for years "back in
> the day" when we used oids in user tables, and they never made it to oid
> wraparound terratory, because they just didn't churn through that much data.
>
> > But having said that, there isn't any real harm in fixing the OID
> > counter to match what it was. You need to run pg_resetxlog to set the
> > WAL position and XID counter anyway, and it can set the OID counter too.
> >
>
> +1 for doing this, otherwise we need some strong warnings in the migrator docs
> about this case imho.

One compromise is outputting the pg_resetxlog command to the terminal,
and suggesting they run it only if they need to.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ If your life is a hard drive, Christ can be your backup. +