Re: found xmin from before relfrozenxid on pg_catalog.pg_authid

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