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

Hi

On Tue, Mar 1, 2011 at 11:00 AM, Heikki Linnakangas <
heikki(dot)linnakangas(at)enterprisedb(dot)com> 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.
>
>
> --
> Heikki Linnakangas
> EnterpriseDB http://www.enterprisedb.com
>

Sorry, I was a bit busy lately.
This effect on my production servers seems have floating nature (some weeks
it happen each day many time and some weeks - not at all... phase of the
moon may be). Last 2 weeks I don't see that error in database logs so I
can't add anything more.

What make situation even harder to debug it is I can't compile and install
patched version of database engine (because it is production server and I
physically don't have access to changing software there). So I trying to
reproduce error on single connect (so I can attach GDB and look inside) but
without luck during last week.

--
Maxim Boguk
Senior Postgresql DBA.

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