On Sat, Jan 27, 2007 at 12:11:59AM +0000, Gregory Stark wrote:
> If this isn't run for a very long time (how long depends on how busy the
> database is, but even on extremely large databases it's usually a matter of
> months, on more normal databases it would be years) then very old records seem
> to suddenly disappear. There is a way to recover data that this has happened
> to though as long as you don't run vacuum after the data has disappeared.
>
> To repeat: If you think this may have happened DO NOT run vacuum now.
Actually, for XID wraparound a VACUUM may actually be the right thing.
I looked at this (with guidence from Tom) and we came to the conclusion
that XID wraparound will hide tuples older than 2 billion transaction,
but VACUUM will mark as frozen anything newer than 3 billion
transactions, so for 1 billion transactions you can actually get your
data back.
Expect for things like uniqueness guarentees, but they're solvable.
Not that I'm saying that the OP has this issue...
Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.