Re: Re: [COMMITTERS] pgsql: Invent a memory context reset/delete callback mechanism.

* Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
> Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> > On Fri, 2015-02-27 at 22:17 +0000, Tom Lane wrote:
> >> In passing, per discussion, rearrange some boolean fields in struct
> >> MemoryContextData so as to avoid wasted padding space. For safety,
> >> this requires making allowInCritSection's existence unconditional;
> >> but I think that's a better approach than what was there anyway.
>
> > I notice that this uses the bytes in MemoryContextData that I was hoping
> > to use for the memory accounting patch (for memory-bounded HashAgg).
>
> Meh. I thought Andres' complaint about that was unfounded anyway ;-).
> But I don't really see why a memory accounting patch should be expected to
> have zero footprint.

For my 2c, I agree that it's a bit ugly to waste space due to padding,
but I'm all about improving the memory accounting and would feel that's
well worth having a slightly larger MemoryContextData.

In other words, I agree with Tom that it doesn't need to have a zero
footprint, but disagree about wasting space due to padding. :D

Thanks!

Stephen