On Wed, 20 Feb 2019 at 21:35, Merlin Moncure <mmonc...@gmail.com> wrote: > > On Mon, Feb 18, 2019 at 9:49 AM Bob Jolliffe <bobjolli...@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.
