Re: found xmin from before relfrozenxid on pg_catalog.pg_authid

On Tue, May 22, 2018 at 9:47 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:

> Hi,
>
> On 2018-05-22 21:30:43 +0300, Maxim Boguk wrote:
> > ​For sample:
> >
> > postgres=# vacuum pg_catalog.pg_authid;
> > ERROR: found xmin 2894889518 from before relfrozenxid 248712603
> >
> > select ctid, xmin, xmax, cmin, cmax from pg_catalog.pg_authid where
> > xmin::text::bigint=2894889518;
> > ctid | xmin | xmax | cmin | cmax
> > --------+------------+------+------+------
> > (1,26) | 2894889518 | 0 | 0 | 0
> >
> >
> > postgres=# SELECT * FROM heap_page_items(get_raw_page('pg_authid', 1))
> > where t_ctid::text='(1,26)';
> > -[ RECORD 1
> > ]-----------------------------------------------------------
> ------------------------------------------------------------
> ------------------------------------------------------------
> ------------------------------------------------------------
> ------------------------------------------------------------------------
> > lp | 26
> > lp_off | 4656
> > lp_flags | 1
> > lp_len | 144
> > t_xmin | 2894889518
> > t_xmax | 0
> > t_field3 | 0
> > t_ctid | (1,26)
> > t_infomask2 | 32779
> > t_infomask | 10507
> > t_hoff | 32
> > t_bits | 1111111111000000
> > t_oid | 189787727
> >
>
> So this row has, if I didn't screw up decoding the following infomask
> bits set::
> HEAP_HASNULL
> HEAP_HASVARWIDTH
> HEAP_HASOID
> HEAP_XMIN_COMMITTED
> HEAP_XMAX_INVALID
> HEAP_UPDATED
>
> So it's not been previously frozen, which I was wondering about.
>
>
> > Which indeed makes it
> > Any new role created in DB instantly affected by this issue.
>
> What's txid_current()?
>
>
> >
> > In the same time:
> >
> > select relfrozenxid from pg_class where relname='pg_authid';
> > relfrozenxid
> > --------------
> > 2863429136
> >
> > So it's interesting where value of " from before relfrozenxid 248712603"
> > come from.
>
> Hm. That's indeed odd. Could you get a backtrace of the error with "bt
> full" of the error?
>
> Greetings,
>
> Andres Freund
>

​select txid_current();
txid_current
--------------
41995913769
​
​About gdb bt - it's tricky because it is mission critical master db of
huge project.
I'll will try promote backup replica and check is issue persist there and
if yes - we will have our playground for a while, but it will require
sometime to arrange.​

--
Maxim Boguk
Senior Postgresql DBA
http://dataegret.com/ <http://www.postgresql-consulting.com/>

Phone RU: +7 985 433 0000
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Skype: maxim.boguk

"Доктор, вы мне советовали так не делать, но почему мне по-прежнему больно
когда я так делаю ещё раз?"