Re: Index Scans become Seq Scans after VACUUM ANALYSE

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> >> Does anyone know what the major barriers to infinite log replay are in
> >> PostgreSQL? I'm trying to look for everything that might need to be
> >> changed outside xlog.c, but surely this has come up before. Searching
> >> the archives hasn't revealed much.
>
> > This has been brought up. Could we just save WAL files and get replay?
> > I believe some things have to be added to WAL to allow this, but it
> > seems possible.
>
> The Red Hat group has been looking at this somewhat; so far there seem
> to be some minor tweaks that would be needed, but no showstoppers.

Good.

> > Somehow you would need a tar-type
> > backup of the database, and with a running db, it is hard to get a valid
> > snapshot of that.
>
> But you don't *need* a "valid snapshot", only a correct copy of
> every block older than the first checkpoint in your WAL log series.
> Any inconsistencies in your tar dump will look like repairable damage;
> replaying the WAL log will fix 'em.

Yes, my point was that you need physical file backups, not pg_dump, and
you have to be tricky about the files changing during the backup. You
_can_ work around changes to the files during backup.

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