Re: incoherent dead tuples between pg_stat_user_tables and pgstattuple?

Luca Ferrari <fluca1978(at)gmail(dot)com> writes:
> On Fri, Sep 27, 2019 at 3:52 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> n_live_tup/n_dead_tup should not be thought to be better than
>> approximations. Most operations adjust them only incrementally,
>> and messages to the stats collector can get dropped entirely
>> under heavy load, causing deltas to go missing. There are
>> also race conditions involved in some update scenarios.

> Are you suggesting tha autovacuum made free space available so that
> pg_stat_user_tables lags behind? Because I don't see last_autovacuum
> changing in the mantime.

I'm not suggesting any specific scenario, because you haven't presented
any evidence as to when those counts became off. I'm just saying that
there are plenty of possible mechanisms for them to become so.

regards, tom lane