Re: PostgreSQL “tuple already updated by self”

On Tue, May 22, 2018 at 8:01 AM, SG <combatcode(at)gmail(dot)com> wrote:
> Our database seems to be broken, normally it uses about 1-2% of cpu, but if
> we run some additional backend services making UPDATE and INSERT queries for
> 10M rows table (about 1 query per 3 second) everything is going to hell
> (including CPU increase from 2% to 98% usage).
>
> We have decided to debug what's going on, run VACUUM and ANALYZE to learn
> what's wrong with db but...
>
> production=# ANALYZE VERBOSE users_user;
> INFO: analyzing "public.users_user"
> INFO: "users_user": scanned 280 of 280 pages, containing 23889 live rows
> and 57 dead rows; 23889 rows in sample, 23889 estimated total rows
> INFO: analyzing "public.users_user"
> INFO: "users_user": scanned 280 of 280 pages, containing 23889 live rows
> and 57 dead rows; 23889 rows in sample, 23889 estimated total rows
> ERROR: tuple already updated by self
>
> we are not able to finish ANALYZE on ANY of the tables and could not find
> any information about this issue. Any suggestions what can be wrong?

Well, as Laurenz Albe said on the Stack Overflow thread, it sure looks
like ANALYZE is finding the same table (public.users_user) twice,
which it shouldn't do. So something is probably wrong with pg_class.
He suggested a duplicate heap tuple, which could well be right, or
maybe it's a broken HOT chain or a bad index or something. If it were
me, I'd probably try what he suggested and then get busy with
pageinspect and/or pg_filedump if that didn't work.

Another interesting question is how the system got into this state in
the first place, of course. Was it a bug, or did you do something
that corrupted the database?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company