Re: Help me recovering data

On Fri, 18 Feb 2005 04:38 pm, Kevin Brown wrote:
> Tom Lane wrote:
> > Gaetano Mendola <mendola(at)bigfoot(dot)com> writes:
> > > BTW, why not do an automatic vacuum instead of shutdown ? At least the
> > > DB do not stop working untill someone study what the problem is and
> > > how solve it.
> >
> > No, the entire point of this discussion is to whup the DBA upside the
> > head with a big enough cluestick to get him to install autovacuum.
> >
> > Once autovacuum is default, it won't matter anymore.
>
> I have a concern about this that I hope is just based on some
> misunderstanding on my part.
>
> My concern is: suppose that a database is modified extremely
> infrequently? So infrequently, in fact, that over a billion read
> transactions occur before the next write transaction. Once that write
> transaction occurs, you're hosed, right? Autovacuum won't catch this
> because it takes action based on the write activity that occurs in the
> tables.
>
> So: will autovacuum be coded to explicitly look for transaction
> wraparound, or to automatically vacuum every N number of transactions
> (e.g., 500 million)?
>
autovacuum already checks for both Transaction wraparound, and table updates.
It vacuums individual tables as they need it, from a free space/recovery point of view.

It also does checks to ensure that no database is nearing transaction wraparound, if it
is, it initiates a database wide vacuum to resolve that issue.

Regards

Russell Smith
>
>