Re: Lowering the ever-growing heap->pd_lower

On Wed, Mar 31, 2021 at 2:49 AM Matthias van de Meent
<boekewurm+postgres(at)gmail(dot)com> wrote:
> I had implemented it locally, but was waiting for some more feedback
> before posting that and got busy with other stuff since, it's now
> attached.
>
> I've also played around with marking the free space on the page as
> undefined for valgrind, but later realized that that would make the
> test for defined memory in PageAddItemExtended fail. This is
> documented in the commit message of the attached patch 0002.

I would like to deal with this work within the scope of the project
we're discussing over on the "New IndexAM API controlling index vacuum
strategies" thread. The latest revision of that patch series includes
a modified version of your patch:

https://postgr.es/m/CAH2-Wzn6a64PJM1Ggzm=uvx2otsopJMhFQj_g1rAj4GWr3ZSzw@mail.gmail.com

Please take discussion around this project over to that other thread.
There are a variety of issues that can only really be discussed in
that context.

Note that I've revised the patch so that it runs during VACUUM's
second heap pass only -- not during pruning/defragmentation. This
means that the line pointer array truncation mechanism will only ever
kick-in during a VACUUM operation.

--
Peter Geoghegan