On Thu, 2024-04-25 at 14:33 -0400, Robert Haas wrote:
> I believe that the underlying problem here can be summarized in this
> way: just because I'm OK with 2MB of bloat in my 10MB table doesn't
> mean that I'm OK with 2TB of bloat in my 10TB table. One reason for
> this is simply that I can afford to waste 2MB much more easily than I
> can afford to waste 2TB -- and that applies both on disk and in
> memory.
I don't find that convincing. Why are 2TB of wasted space in a 10TB
table worse than 2TB of wasted space in 100 tables of 100GB each?
> Another reason, at least in existing releases, is that at some
> point index vacuuming hits a wall because we run out of space for dead
> tuples. We *most definitely* want to do index vacuuming before we get
> to the point where we're going to have to do multiple cycles of index
> vacuuming.
That is more convincing. But do we need a GUC for that? What about
making a table eligible for autovacuum as soon as the number of dead
tuples reaches 90% of what you can hold in "autovacuum_work_mem"?
Yours,
Laurenz Albe