Re: pg_shmem_allocations & documentation

At Fri, 11 Dec 2020 14:42:45 +0900, Michael Paquier <michael(at)paquier(dot)xyz> wrote in
> On Fri, Dec 11, 2020 at 11:00:58AM +0900, Kyotaro Horiguchi wrote:
> > Although we could just rip some words off, I'd like to propose instead
> > to add an explanation why it is not exposed for anonymous allocations,
> > like the column allocated_size.
>
> Indeed, there is a hiccup between what the code does and what the docs
> tell: the offset is not NULL for unused memory.
>
> > - The offset at which the allocation starts. NULL for anonymous
> > - allocations and unused memory.
> > + The offset at which the allocation starts. For anonymous allocations,
> > + no information about individual allocations is available, so the column
> > + will be NULL in that case.
>
> I'd say: let's be simple and just remove "and unused memory" because
> anonymous allocations are... Anonymous so you cannot know details
> related to them. That's something easy to reason about, and the docs
> were written originally to remain simple.

Hmm. I don't object to that. Howerver, isn't the description for
allocated_size too verbose in that sense?

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center