Re: [SQL] EXTERNAL storage and substring on long strings

Scott Cain <cain@cshl.org> writes:
> At least this appears to work and is much faster, completing substring
> operations like above in about 0.27 secs (that's about two orders of
> magnitude improvement!)

I find it really, really hard to believe that a crude reimplementation
in plpgsql of the TOAST concept could beat the built-in implementation
at all, let alone beat it by two orders of magnitude.

Either there's something unrealistic about your testing of the
dna_string function, or your original tests are not causing TOAST to be
invoked in the expected way, or there's a bug we need to fix.  I'd
really like to see some profiling of the poor-performing
external-storage case, so we can figure out what's going on.

            regards, tom lane