Re: [PATCH] backend: compare word-at-a-time in bcTruelen

Stephen Frost wrote:
> * Stefan Kaltenbrunner (stefan(at)kaltenbrunner(dot)cc) wrote:
>> FWIW: I'm able to measure an even more significant improvement of around
>> 10%:
>
> What would be really useful would be "best case" and "worst case"
> scenarios. Ideally, with profile information for this specific function
> (in addition to full benchmark runs since those can show minimal
> performance improvments due to other constraints, locking, etc).

not sure what you are after here - my testcase is one specific query run
in parallel on 16 processes (running it in a single process yields
similiar improvements our scaling is pretty good here).

>
> Have you tried pulling this function out and running tests with all
> alignment possibilities to see how it compares to the original? There's
> only so many options and showing that this change always improves
> performance, or at least doesn't degrade it in the worst case, would
> certainly go a long way towards getting it accepted.

again I'm not exactly sure on what you want to get tested specifically -
the original problem report was because I noticed a significant
performance improvement from using varchar() instead of char(n) and that
showed bcTruelen() on the very top of the profile.
I was simply testing the patch Jeremy provided on that workload(the
upthread mentioned query is mostly affected by that on others there is
no measurable difference)

Stefan