Re: BUG #16098: unexplained autovacuum to prevent wraparound

On Fri, Nov 8, 2019 at 2:37 PM Alessandro Ferraresi <
alessandro(dot)ferraresi1(at)gmail(dot)com> wrote:

>
> Autovacuum to prevent wrap around kicks in on those table, I was actually
> wondering if this is somehow related to *autovacuum_multixact_freeze_max_age
> *parameter and how. That behavior should be referred to row locking on
> multiple transaction but this database is still static and not accessible
> yet, meaning there shouldn't be row level concurrency. For completeness,
> the load for each table is executed by 40 parallel sessions running the
> copy command.
>

I would think 40 parallel sessions loading data would exactly trigger
multixact, if you have foreign key constraints in place at the time. Each
parent row has be locked by each parallel session, to make sure the parent
row doesn't go away (or have the key changed) while the child insert is
happening.

Cheers,

Jeff

>