Re: B-Tree support function number 3 (strxfrm() optimization)

On Mon, Sep 15, 2014 at 4:21 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> I attach a much simpler patch, that only adds an opportunistic
> "memcmp() == 0" before a possible strcoll(). Both
> bttextfastcmp_locale() and varstr_cmp() have the optimization added,
> since there is no point in leaving anyone out for this part.

FWIW, it occurs to me that this could be a big win for cases like
ExecMergeJoin(). Obviously, abbreviated keys will usually make your
merge join on text attributes a lot faster in the common case where a
sort is involved (if we consider that the sort is integral to the cost
of the join). However, when making sure that inner and outer tuples
match, the MJCompare() call will *very* frequently get away with a
cheap memcmp(). That could make a very significant additional
difference, I think.

--
Peter Geoghegan