Re: pgsql 10.23 , different systems, same table , same plan, different Buffers: shared hit

On Sat, Sep 16, 2023 at 7:42 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Sadly, this proves very little about Linux's behavior.  glibc's idea
> of en_US involves some very complicated multi-pass sort rules.
> AFAICT from the FreeBSD sort(1) man page, FreeBSD defines en_US
> as "same as C except case-insensitive", whereas I'm pretty sure
> that underscores and other punctuation are nearly ignored in
> glibc's interpretation; they'll only be taken into account if the
> alphanumeric parts of the strings sort equal.

Achilleas didn't mention the glibc version, but based on the kernel
vintage mentioned I guess that must be the "old" (pre 2.28) glibc
sorting.  In 2.28 they did a big sync-up with ISO 14651, while FreeBSD
follows the UCA, a closely related standard[1].  I think newer
Linux/glibc systems should agree with FreeBSD's libc in more cases
(and also agree with ICU).

[1] https://unicode.org/reports/tr10/#Synch_ISO14651