Re: [HACKERS] another locale problem

Tom,

So you say that this check prevents the use of indexes, when we use the ~* 
operator and have alpha characters in the pattern, because apparently the 
index cannot do case insensitive matching.

I was under the (apparently wrong impression) that it was possible to use 
indexes for case insensitive matching. Dreaming... :-)

For your information, isalpha() is the correct match for case foldable 
characters, at least in the cp1251 (windows-1251) locale. I believe a more 
correct test could be to access the locale's MAPLOWER and MAPUPPER tables.

It is not the case in Bulgarian, but there might be languages where an letter 
does not exist in both upper and lower cases and therefore requires more 
complex handling. Perhaps such situation exists in the multibyte locales.

Please excuse my confusion. :-)

Daniel

>>>Tom Lane said:> Daniel Kalchev <daniel@digsys.bg> writes:> > In fact, after giving it some though... the expression
ingram.y> > >                         (strcmp(opname,"~*")> > == 0 && isalpha(n->val.val.str[pos])))> > > is wrong. The
statementin my view decides that a regular expression is no    t > > indexable if it contains special characters or if
itcontains non-alpha > > characters. Therefore, the statement should be written as:> > >
(strcmp(opname,"~*")>> == 0 && !isalpha((unsigned char)n->val.val.str[pos])))> > No, it's not wrong, at least not in
thatway!  You've missed the point> entirely.  ~* is the *case insensitive* regexp match operator.> Therefore if I have
apattern like '^abc' it can match anything> beginning with either 'a' or 'A'.  If the index restriction were to>
includethe letter 'a' then it would exclude valid matches starting with> 'A'.  The simplest solution, which is what's
inmakeIndexable(), is> to exclude case-foldable characters from the index restriction pattern.> In this particular case
youend up getting no index restriction at all,> but that is indeed what's supposed to happen.> > I am not sure that
isalpha()is an adequate test for case-foldable> characters in non-ASCII locales, but inverting it is definitely wrong
;-)>>             regards, tom lane