Re: [HACKERS] Re: PD_ALL_VISIBLE flag was incorrectly set happend during repeatable vacuum

On Tue, Mar 01, 2011 at 12:00:54AM +0200, Heikki Linnakangas wrote:
> On 28.02.2011 23:28, daveg wrote:
> >On Wed, Jan 12, 2011 at 10:46:14AM +0200, Heikki Linnakangas wrote:
> >>We'll likely need to go back and forth a few times with various
> >>debugging patches until we get to the heart of this..
> >
> >Anything new on this? I'm seeing at on one of my clients production boxes.
> 
> I haven't heard anything from the OP since.
> 
> >Also, what is the significance, ie what is the risk or damage potential if
> >this flag is set incorrectly?
> 
> Sequential scans will honor the flag, so you might see some dead rows 
> incorrectly returned by a sequential scan. That's the only "damage", but 
> an incorrectly set flag could be a sign of something more sinister, like 
> corrupt tuple headers. The flag should never be set incorrectly, so if 
> you see that message you have hit a bug in PostgreSQL, or you have bad 
> hardware.
> 
> This flag is quite new, so a bug in PostgreSQL is quite possible. If you 
> still have a backup that contains those incorrectly set flags, I'd like 
> to see what the page looks like.


I ran vacuums on all the affected tables last night. I plan to take a downtime
to clear the buffer cache and then to run vacuums on all the dbs in the
cluster.

Most but not all the tables involved are catalogs.

However, I could probably pick up your old patch sometime next week if it
recurrs and send you page images.

-dg

-- 
David Gould       daveg@sonic.net      510 536 1443    510 282 0869
If simplicity worked, the world would be overrun with insects.