On Wed, 20 Feb 2019 at 21:35, Merlin Moncure <mmoncure@gmail.com> wrote:
>
> On Mon, Feb 18, 2019 at 9:49 AM Bob Jolliffe <bobjolliffe@gmail.com> wrote:
> >
> > Sorry Merlin for not replying earlier. The difference is indeed hard
> > to understand but it is certainly there. We altered the collation to
> > use on the name field in that table and the problem has gone. Having
> > having solved the immediate problem we haven't investigated much
> > further yet.
> >
> > Not sure what exactly you mean by "other conversions"?
>
>
> I hand tested similar query for other (generally western) collations.
> Did not observe anything nearly so bad. What I'm hoping is that this
> is some kind of weird performance issue specific to your installation;
> in the worst (unfortunately likely) case we are looking at something
> specific to your specific sort collation :(.
>
It seems not to be (completely) particular to the installation.
Testing on different platforms we found variable speed difference
between 100x and 1000x slower, but always a considerable order of
magnitiude. The very slow performance comes from sorting Lao
characters using en_US.UTF-8 collation.