Re: Emit fewer vacuum records by reaping removable tuples during pruning

On Tue, Jan 16, 2024 at 4:28 PM Jim Nasby <jim(dot)nasby(at)gmail(dot)com> wrote:
> On 1/12/24 12:45 PM, Robert Haas wrote:
> > P.P.S. to everyone: Yikes, this logic is really confusing.
>
> Having studied all this code several years ago when it was even simpler
> - it was *still* very hard to grok even back then. I *greatly
> appreciate* the effort that y'all are putting into increasing the
> clarity here.

Thanks. And yeah, I agree.

> BTW, back in the day the whole "no indexes" optimization was a really
> tiny amount of code... I think it amounted to 2 or 3 if statements. I
> haven't yet attempted to grok this patchset, but I'm definitely
> wondering how much it's worth continuing to optimize that case. Clearly
> it'd be very expensive to memoize dead tuples just to trawl that list a
> single time to clean the heap, but outside of that I'm not sure other
> optimazations are worth it given the amount of code
> complexity/duplication they seem to require - especially for code where
> correctness is so crucial.

Personally, I don't think throwing away that optimization is the way
to go. The idea isn't intrinsically complicated, I believe. It's just
that the code has become messy because of too many hands touching it.
At least, that's my read.

--
Robert Haas
EDB: http://www.enterprisedb.com