On Wed, Jun 14, 2023 at 12:50:28PM +0200, Juan José Santamaría Flecha wrote: > On Wed, Jun 14, 2023 at 4:13 AM Peter Geoghegan <p...@bowt.ie> wrote: > > > On Tue, Jun 13, 2023 at 5:59 PM Thomas Munro <thomas.mu...@gmail.com> > > wrote: > > > Trying to follow along here... you're doing the moral equivalent of > > > strxfrm(), so sort keys have the transitive property but direct string > > > comparisons don't? Or is this because LCIDs reach a different > > > algorithm somehow (or otherwise why do you need to use LCIDs for this, > > > when there is a non-LCID version of that function, with a warning not > > > to use the older LCID version[1]?) > > > > I'm reminded of the fact that the abbreviated keys strxfrm() debacle > > (back when 9.5 was released) was caused by a bug in strcoll() -- not a > > bug in strxfrm() itself. From our point of view the problem was that > > strxfrm() failed to be bug compatible with strcoll() due to a buggy > > strcoll() optimization. > > > > I believe that strxfrm() is generally less likely to have bugs than > > strcoll(). There are far fewer opportunities to dodge unnecessary work > > in the case of strxfrm()-like algorithms (offering something like > > ICU's pg_strnxfrm_prefix_icu() prefix optimization is the only one). > > On the other hand, collation library implementers are likely to > > heavily optimize strcoll() for typical use-cases such as sorting and > > binary search. Using strxfrm() for everything is discouraged [1]. > > > > Yes, I think the situation is quite similar to what you describe, with its > WIN32 peculiarities. Take for example the attached program, it'll output: > > s1 = s2 > s2 = s3 > s1 > s3 > c1 > c2 > c2 > c3 > c1 > c3 > > As you can see the test for CompareStringEx() is broken, but we get a sane > answer with LCMapStringEx().
The LCMapStringEx() solution is elegant. I do see https://learn.microsoft.com/en-us/windows/win32/intl/handling-sorting-in-your-applications says, "If an application calls the function to create a sort key for a string containing an Arabic kashida, the function creates no sort key value." That's aggravating.
