On Thu, May 13, 2021 at 09:47:02PM -0400, Tom Lane wrote: > Julien Rouhaud <rjuju...@gmail.com> writes: > > On Fri, May 14, 2021 at 3:12 AM Bruce Momjian <br...@momjian.us> wrote: > >> I was surprised it was ~2%. > > > Just to be clear, the 2% was a worst case scenario, ie. a very fast > > read-only query on small data returning a single row. As soon as you > > get something more realistic / expensive the overhead goes away. > > Of course, for plenty of people that IS the realistic scenario that > they care about max performance for.
I'm not arguing that the scenario is unrealistic. I'm arguing that retrieving the first row of a join between pg_class and pg_attribute on an otherwise vanilla database may not be the most representative workload, especially when you take into account that it was done on hardware that still took 3 ms to do that. Unfortunately my laptop is pretty old and has already proven multiple time to give unreliable benchmark results, so I'm not confident at all that those 2% are even real outside of my machine.
