strxfrm output stability
Paul Eggert
eggert@cs.ucla.edu
Wed Sep 9 16:45:00 GMT 2015
Florian Weimer wrote:
>> >I'll go out on a limb and say that no sane application uses strxfrm,
>> >either on disk or off.
> PostgreSQL uses it to avoid calling strcoll on strings which have
> distinctly ordered prefixes in their strxfrm output.
Good catch, and that is what I get for going out on a limb.
Although after looking at it a bit, it is not a true counterexample, as the
PostgreSQL code is crazy. For example, it inspects strxfrm output for
upper-case ASCII letters?! Overall PostgreSQL's use of strxfrm has the smell of
someone applying theory from the 1970s without having measured whether
performance actually improves in the typical case nowadays. and it might be
amusing to replace PostgreSQL's use of strxfrm with a function that always
returns the empty string; the code would still work, and might even run faster.
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