Re: [PoC] Improve dead tuple storage for lazy vacuum

Hi,

On 2021-07-29 13:15:53 -0400, Robert Haas wrote:
> I don't know if this is better, but I do kind of like the fact that
> the basic representation is just an array. It makes it really easy to
> predict how much memory will be needed for a given number of dead
> TIDs, and it's very DSM-friendly as well.

I think those advantages are far outstripped by the big disadvantage of
needing to either size the array accurately from the start, or to
reallocate the whole array.  Our current pre-allocation behaviour is
very wasteful for most vacuums but doesn't handle large work_mem at all,
causing unnecessary index scans.

Greetings,

Andres Freund