Hi everyone,
I just got the same issue on 9.6.8:
2018-05-15 11:52:01 MSK 33558 @ from [vxid:317/92895305 txid:0] [] ERROR: found xmin 2808837517 from before relfrozenxid 248712603
2018-05-15 11:52:01 MSK 33558 @ from [vxid:317/92895305 txid:0] [] CONTEXT: automatic vacuum of table "template0.pg_catalog.pg_authid"
Additional details:
1) bt_index_check - no errors on both indexes.
2) SELECT pg_truncate_visibility_map('pg_authid'::regclass); + vacuum freeze - doesn't help.
3)Total 6 rows affected:
template1=# select oid, ctid, xmin, xmax, cmin, cmax from pg_authid where xmin::text::bigint > (select relfrozenxid::text::bigint from pg_class where relname='pg_authid');
oid | ctid | xmin | xmax | cmin | cmax
-----------+--------+------------+------+------+------
183671986 | (0,90) | 3039161773 | 0 | 0 | 0
183106699 | (1,48) | 2576823237 | 0 | 0 | 0
183921770 | (1,50) | 3265971811 | 0 | 0 | 0
183921914 | (1,52) | 3266122344 | 0 | 0 | 0
187988173 | (1,58) | 4258893789 | 0 | 0 | 0
182424977 | (1,62) | 2808837517 | 0 | 0 | 0
on total two pages.
4) template1=# select relfrozenxid from pg_catalog.pg_class where relname = 'pg_authid';
relfrozenxid
--------------
2548304492
5)Rows itself looks pretty valid and correspond to the actual database users.
7)No database/server crash happened last few years, no disk errors/problems.
I feel it could be related with vacuum skip locked pages patch + freeze + shared catalog combination, but cannot prove it yet.
Looking for possible course of action.
Probably simplest fix - drop and recreate these 6 affected users, but so far I willing spent some time research into this issue.