Re: PATCH: CITEXT 2.0 v4

On Wednesday 16 July 2008 13:54:25 David E. Wheeler wrote:
> On Jul 15, 2008, at 22:23, David E. Wheeler wrote:
> > * The README for citext 1.0 on pgFoundry says:
> >> I had to make a decision on casting between types for regular
> >> expressions and
> >> decided that if any parameter is of citext type then case
> >> insensitive applies.
> >> For example applying regular expressions with a varchar and a
> >> citext will
> >> produce a case-insensitive result.
> >>
> >> Having thought about this afterwards I realised that since we have
> >> the option
> >> to use case-insensitive results with regular expressions I should
> >> have left the
> >> behaviour exactly as text and then you have the best of both
> >> worlds... oh well
> >> not hard to change for any of you perfectionists!
> >
> > I followed the original and made all the regex and LIKE comparisons
> > case-insensitive. But maybe I should not have? Especially since the
> > regular expression functions (e.g., regexp_replace()) and a few non-
> > regex functions (e.g., replace()) still don't behave case-
> > insensitively?
>
> I was thinking about this a bit last night and wanted to fill things
> out a bit.
>
> As a programmer, I find Donald Fraser's hindsight to be more
> appealing, because at least that way I have the option to do matching
> against CITEXT strings case-sensitively when I want to.
>
> OTOH, if what we want is to have CITEXT work more like a case-
> insensitive collation, then the expectation from the matching
> operators and functions might be different. Does anyone have any idea
> whether regex and LIKE matching against a string in a case-insensitive
> collation would match case-insensitively or not? If so, then maybe the
> regex and LIKE ops and funcs *should* match case-insensitively? If
> not, or if only for some collations, then I would think not.
>
> Either way, I know of no way, currently, to allow functions like
> replace(), split_part(), strpos(), and translate() to match case-
> insensitiely, even if we wanted to. Anyone have any ideas?
>
> > * If the answer is "no", how can I make those functions behave case-
> > insensitively? (See the "TODO" tests.)
> >
> > * Should there be any other casts? To and from name, perhaps?
>

AIUI, your propsing the following:

select 'x'::citext = 'X'::citext;
?column?
----------
t
(1 row)

select 'x'::citext ~ 'X'::citext;
?column?
----------
f
(1 row)

I understand the desire for flexibility, but the above seems wierd to me.

--
Robert Treat
Build A Brighter LAMP :: Linux Apache {middleware} PostgreSQL