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