Re: Lowering the ever-growing heap->pd_lower

On Fri, Apr 8, 2022 at 12:57 PM Peter Geoghegan <pg@bowt.ie> wrote:
> What do you mean about wasting space? Wasting space on the stack? I
> can't imagine you meant wasting space on the page, since being able to
> accomodate more items on each heap page seems like it would be
> strictly better, barring any unintended weird FSM issues.

I meant wasting space in the page. I think that's a real concern.
Imagine you allowed 1000 line pointers per page. Each one consumes 2
bytes. So now you could have ~25% of each page in the table storing
dead line pointers. That sounds awful, and just running VACUUM won't
fix it once it's happened, because the still-live line pointers are
likely to be at the end of the line pointer array and thus truncating
it won't necessarily be possible.

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