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

Tom,

> > I've put together some data from a microbenchmark of the bcTrulen
> > function, patched and unpatched.
>
> Uh, where's the data?

If you're after the raw data for a run, I've put it up:

http://ozlabs.org/~jk/projects/db/data/bctruelen.csv

I've also packaged up the quick-and-dirty benchmark I've been using:

http://ozlabs.org/~jk/projects/db/bctrulen.tar.gz

to recreate as-needed. ./benchmark.sh will run tests for varying-length
strings (so changing the alignment) and varying numbers of trailing
spaces. ./benchmark-bctruelen <str> will perform an individual old/new
comparison.

> Unfortunately, the cases with lots of padding spaces are probably
> much less probable than the cases with fewer. It would be unpleasant
> for example if this patch resulted in a severe performance
> degradation for a "canonical" example of char(n) being used properly,
> such as char(2) for US state abbreviations.

Yep, makes sense. The other consideration is stock-ticker symbols, I
assume they may also be stored in CHAR(small n) columns.

Cheers,

Jeremy