Re: Odd code around ginScanToDelete

Hi, Xuneng

> > Is it worth/possible in recursive calls of ginScanToDelete() to free
> > allocated myStackItem->child after processing all children of the
> > current level, when they are not needed anymore?
> > Previously to this patch, palloc-ed "me" variable also was't freed at
> > recursion levels.
>
> Freeing/reallocating it per subtree would add churn and make the
> lifetime rules harder to reason about without meaningful memory
> savings (the number of nodes is bounded by tree depth, not number of
> pages). We currently free the chain once after ginScanToDelete()
> returns in ginVacuumPostingTree(), which matches the natural lifetime
> boundary
I proposed not freeing child when child iteration is complete. They
indeed can be reused. I proposed cleaning children when "my" iteration
is complete. At that time all the children iterations are completed
and not needed when we return level up.

Regards,
Pavel Borisov
Supabase