John Hansen wrote: > Bruce Momjian wrote: > > > > There are two reasons for that optimization --- first, some > > locale support is broken and Unicode encoding with a C locale > > crashes (not an issue for ICU), and second, it is an > > optimization for languages like Japanese that want to use > > unicode, but don't need a locale because upper/lower means > > nothing in those character sets. > > No, upper/lower means nothing in those languages, so why would you need > to optimize upper/lower if they're not used??
True. I suppose it is for databases that use both Japanese and Latin alphabets and run upper() on all values. > And if they are, it's obviously because the text contains characters > from other languages (probably english) and as such they should behave > correctly. > > Did I mention that for japanese and the like, ICU would also offer > transliteration... Interesting. > > So, the first issue doesn't apply for ICU, and the second > > might not depending on what characters you are using in the > > Unicode character set. > > > > I guess I am little confused how ICU can do upper() when the > > locale is C. What is it using to determine A is upper for a? > > Am I confused? > > Simple, UNICODE basically consist of a table of characters > (http://www.unicode.org/Public/UNIDATA/UnicodeData.txt) > > Excerpt: > > 0041;LATIN CAPITAL LETTER A;Lu;0;L;;;;;N;;;;0061; > ... > 0061;LATIN SMALL LETTER A;Ll;0;L;;;;;N;;;0041;;0041 > > >From this you can see, that for 0041, which is capital letter A, there > is a mapping to it's lowercase counterpart, 0061 > Likewise, there is a mapping for 0061 which says it's uppercase > counterpart is 0041. > There is also SpecialCasing.txt which covers those mappings that haven't > got a 1-1 mapping, such as the german SS. > > These mappings are fixed, independent of locale, only a few cases from > specialcasing.txt depend on locale/context. As far as I know, the only way to use Unicode currently is to use a locale that is unicode-aware. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
