Re: Removing more vacuumlazy.c special cases, relfrozenxid optimizations

Hi,

On 2022-02-18 13:09:45 -0800, Peter Geoghegan wrote:
> 0001 is tricky in the sense that there are a lot of fine details, and
> if you get any one of them wrong the result might be a subtle bug. For
> example, the heap_tuple_needs_freeze() code path is only used when we
> cannot get a cleanup lock, which is rare -- and some of the branches
> within the function are relatively rare themselves. The obvious
> concern is: What if some detail of how we track the new relfrozenxid
> value (and new relminmxid value) in this seldom-hit codepath is just
> wrong, in whatever way we didn't think of?

I think it'd be good to add a few isolationtest cases for the
can't-get-cleanup-lock paths. I think it shouldn't be hard using cursors. The
slightly harder part is verifying that VACUUM did something reasonable, but
that still should be doable?

Greetings,

Andres Freund