Re: Berserk Autovacuum (let's save next Mandrill)

On 2019-Mar-27, Darafei "Komяpa" Praliaskouski wrote:

> Attached is sketch of small patch that fixes several edge cases with
> autovacuum. Long story short autovacuum never comes to append only tables,
> killing large productions.

Yeah, autovac is not coping with these scenarios (and probably others).
However, rather than taking your patch's idea verbatim, I think we
should have autovacuum use separate actions for those two (wildly
different) scenarios. For example:

* certain tables would have some sort of partial scan that sets the
visibility map. There's no reason to invoke the whole vacuuming
machinery. I don't think this is limited to append-only tables, but
rather those are just the ones that are affected the most.

* tables nearing wraparound danger should use the (yet to be committed)
option to skip index cleaning, which makes the cleanup action faster.
Again, no need for complete vacuuming.

--
Álvaro Herrera https://www.2ndQuadrant.com/
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