In a database with utf8 encoding, this behaves reasonably:
select count(*) from
(select * from generate_series(1,10000000) xorder by x::text collate "en-x-icu") ss;
It eats circa 25MB, not a lot worse than the libc-collation equivalent.
But try it in say LATIN1, and it eats multiple gigabytes.
I believe the reason is that the code paths in varstr_cmp that make
use of icu_to_uchar() have forgotten to free the palloc'd output
of the latter. I have not looked to see where else the users of
that and the reverse function made this mistake.
regards, tom lane
