Re: suboverflowed subtransactions concurrency performance optimize

On Fri, May 27, 2022 at 8:55 AM Andres Freund <andres@anarazel.de> wrote:
> > Anyway, how about if we clear this cache for subtrans whenever
> > TransactionXmin is advanced and cachedFetchSubXid precedes it? The
> > comments atop SubTransGetTopmostTransaction seem to state that we
> > don't care about the exact topmost parent when the intermediate one
> > precedes TransactionXmin. I think it should preserve the optimization
> > because anyway for such cases there is a fast path in
> > SubTransGetTopmostTransaction.
>
> There's not even a proof this does speed up anything useful! There's not a
> single benchmark for the patch.

I find it hard to believe that there wasn't even a cursory effort at
performance validation before this was committed, but that's what it
looks like.

-- 
Peter Geoghegan