On Fri, Jun 2, 2017 at 2:22 PM, Peter Geoghegan <p...@bowt.ie> wrote: > On Fri, Jun 2, 2017 at 10:34 AM, Amit Khandekar <amitdkhan...@gmail.com> > wrote: >> Ok. I was thinking we are doing the tie-breaker because specifically >> strcoll_l() was unexpectedly returning 0 for some cases. Now I get it, >> that we do that to be compatible with texteq(). > > Both of these explanations are correct, in a way. See commit 656beff.
I have to admit that I'm still a little confused about what's actually going on here. Commit says that it "fixes inconsistent behavior under glibc's hu_HU locale", but it doesn't say what sort of inconsistent behavior it fixes. It added a comment - which remains to this day - saying this: + * In some locales strcoll() can claim that nonidentical strings are + * equal. Believing that would be bad news for a number of reasons, + * so we follow Perl's lead and sort "equal" strings according to + * strcmp(). Again, however, the reasons why believing it would be bad news are not enumerated. It is merely asserted that there is more than one such reason. Now, it is obviously not true in general that a comparison operator can never deem two values which are not byte-for-byte identical as equal, because citext does exactly that (indeed, that's the point). I thought maybe citext could get away with it because it lacked indexing support but, nope, it has indexing support. Also, the in-core numeric data type has the same property ('1.0'::numeric = '1'::numeric, but scale() reveals that they are not byte-for-byte identical). So, what's special about text that it can never report two non-byte-for-byte values as equal? And could we consider changing that, so that users can select an ICU collator and get exactly the behavior ICU delivers, without the extra tiebreak? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers