Re: Index Scans become Seq Scans after VACUUM ANALYSE

Bruce Momjian <pgman@candle.pha.pa.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.

> 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.
        regards, tom lane