Re: Disappearing Records

On Wed, Nov 02, 2005 at 09:46:38AM -0500, Tom Lane wrote:
> Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> > The really nasty thing about it is that because the records are now
> > considered really old, as soon as you do run VACUUM it'll start
> > removing the rows you want to save...
>
> You sure about that? I think VACUUM just tests for "committed or not".
>
> I'm too lazy to set up a test case, but it's possible that VACUUM FREEZE
> would resurrect wrapped-around tuples, or could be made to with only a
> small code tweak.

Well, that would be really nice to be able to tell people. But looking
at the code of HeapTupleSatisfiesVacuum it spends a lot of time
checking hint bits. While we might be able to fiddle the one function,
checking all the places involving the hint bits could be nasty. Or not.

Making a test case would be interesting, I'll look into it sometime I
guess...

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.