On Fri, Jan 31, 2025 at 5:28 PM Joshua Banton <bant...@gmail.com> wrote:
> The issue mostly manifests near the end of the "scanning heap" phase of 
> vacuuming of one of our largest tables, we'll call table1. RDS Performance 
> Insights reports that selects on table1 start to wait on cpu, where 
> previously it didn't even show up in the top 25 queries by wait. It doesn't 
> always happen, but if there is a larger than usual number of selects on 
> table1 it is more likely to happen.

Does this database also have many tables? As in thousands of tables?

I am reminded of this issue:

https://www.postgresql.org/message-id/flat/da3205c4-5b07-a65c-6c26-a293c6464fdb%40postgrespro.ru

I've heard of this happening when an aggressive VACUUM updates
relfrozenxid on a larger table.

-- 
Peter Geoghegan


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