On Sat, Feb 18, 2012 at 7:29 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote: >> Yeah, it's conceivable that we could implement something whereby >> characters with codes above some cutoff point are handled via runtime >> calls to iswalpha() and friends, rather than being included in the >> statically-constructed DFA maps. The cutoff point could likely be a lot >> less than U+FFFF, too, thereby saving storage and map build time all >> round. > > In the meantime, I still think the caching logic is worth having, and > we could at least make some people happy if we selected a cutoff point > somewhere between U+FF and U+FFFF. I don't have any strong ideas about > what a good compromise cutoff would be. One possibility is U+7FF, which > corresponds to the limit of what fits in 2-byte UTF8; but I don't know > if that corresponds to any significant dropoff in frequency of usage.
The problem, of course, is that this probably depends quite a bit on what language you happen to be using. For some languages, it won't matter whether you cut it off at U+FF or U+7FF; while for others even U+FFFF might not be enough. So I think this is one of those cases where it's somewhat meaningless to talk about frequency of usage.
Does it make sense for regexps to have collations?
