Re: Boundary value check in lazy_tid_reaped()

On Tue, Sep 1, 2020 at 7:21 AM Thomas Munro <thomas.munro@gmail.com> wrote:
> On Sun, Aug 30, 2020 at 11:08 PM Masahiko Sawada
> <masahiko.sawada@2ndquadrant.com> wrote:
> > So my proposal is to add boundary value check in lazy_tid_reaped()
> > before executing bsearch(3). This will help when index vacuum happens
> > multiple times or when garbage tuples are concentrated to a narrow
> > range.
>
> Makes sense if it's often out of range.

... though I'm not sure why you need to add extra members to do it?

> > I thought that we can have a generic function wrapping bsearch(3) that
> > does boundary value checks and then does bsearch(3) so that we can use
> > it in other similar places as well. But the attached patch doesn't do
> > that as I'd like to hear opinions on the proposal first.
>
> I wonder if you would also see a speed-up with a bsearch() replacement
> that is inlineable, so it can inline the comparator (instead of
> calling it through a function pointer).  I wonder if something more
> like (lblk << 32 | loff) - (rblk << 32 | roff) would go faster than
> the branchy comparator.

Erm, off course that expression won't work... should be << 16, but
even then it would only work with a bsearch that uses int64_t
comparators, so I take that part back.