Re: New strategies for freezing, advancing relfrozenxid early

On Wed, Jan 25, 2023 at 8:49 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> The concrete setting of vacuum_freeze_strategy_threshold doesn't matter.
> Table size simply isn't a usable proxy for whether eager freezing is a good
> idea or not.

I strongly agree. I can't imagine how a size-based threshold can make
any sense at all.

Both Andres and I have repeatedly expressed concern about how much is
being changed in the behavior of vacuum, and how quickly, and IMHO on
the basis of very limited evidence that the changes are improvements.
The fact that Andres was very quickly able to find cases where the
patch produces large regression is just more evidence of that. It's
also hard to even understand what has been changed, because the
descriptions are so theoretical.

I think we're on a very dangerous path here. I want VACUUM to be
better as the next person, but I really don't believe that's the
direction we're headed. I think if we release like this, we're going
to experience more VACUUM pain, not less. And worse still, I don't
think anyone other than Peter and Andres is going to understand why
it's happening.

--
Robert Haas
EDB: http://www.enterprisedb.com