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Re: Unicode combining characters

From: Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp>
To: pgman(at)candle(dot)pha(dot)pa(dot)us
Cc: phede-ml(at)islande(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Unicode combining characters
Date: 2001-10-02 01:14:16
Message-ID: 20011002101416E.t-ishii@sra.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackers
> Can someone give me TODO items for this discussion?

What about:

Improve Unicode combined character handling
--
Tatsuo Ishii

> > > So, this shows two problems :
> > > 
> > > - length() on the server side doesn't handle correctly Unicode [I have
> > >   the same result with char_length()], and returns the number of chars
> > >   (as it is however advertised to do), rather the length of the
> > >   string.
> > 
> > This is a known limitation.
> > 
> > > - the psql frontend makes the same mistake.
> > >
> > > I am using version 7.1.3 (debian sid), so it may have been corrected
> > > in the meantime (in this case, I apologise, but I have only recently
> > > started again to use PostgreSQL and I haven't followed -hackers long
> > > enough).
> > > 
> > > 
> > > => I think fixing psql shouldn't be too complicated, as the glibc
> > > should be providing the locale, and return the right values (is this
> > > the case ? and what happens for combined latin + chinese characters
> > > for example ? I'll have to try that later). If it's not fixed already,
> > > do you want me to look at this ? [it will take some time, as I haven't
> > > set up any development environment for postgres yet, and I'm away for
> > > one week from thursday].
> > 
> > Sounds great.
> > 
> > > I was wondering if some people have already thought about this, or
> > > already done something, or if some of you are interested in this. If
> > > nobody does anything, I'll do something eventually, probably before
> > > Christmas (I don't have much time for this, and I don't need the
> > > functionality right now), but if there is an interest, I could team
> > > with others and develop it faster :)
> > 
> > I'm very interested in your point. I will start studying [1][2] after
> > the beta freeze.
> > 
> > > Anyway, I'm open to suggestions :
> > > 
> > > - implement it in C, in the core,
> > > 
> > > - implement it in C, as contributed custom functions,
> > 
> > This may be a good starting point.
> > 
> > > I can't really accept a solution which would rely on the underlaying
> > > libc, as it may not provide the necessary locales (or maybe, then,
> > 
> > I totally agree here.
> > 
> > > The main functions I foresee are :
> > > 
> > > - provide a normalisation function to all 4 forms,
> > > 
> > > - provide a collation_key(text, language) function, as the calculation
> > >   of the key may be expensive, some may want to index on the result (I
> > >   would :) ),
> > > 
> > > - provide a collation algorithm, using the two previous facilities,
> > >   which can do primary to tertiary collation (cf TR#10 for a detailed
> > >   explanation).
> > > 
> > > I haven't looked at PostgreSQL code yet (shame !), so I may be
> > > completely off-track, in which case I'll retract myself and won't
> > > bother you again (on that subject, that is ;) )...
> > > 
> > > Comments ?
> > --
> > Tatsuo Ishii
> > 
> > ---------------------------(end of broadcast)---------------------------
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> 
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
>   +  If your life is a hard drive,     |  830 Blythe Avenue
>   +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026
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Subject: Re: Unicode combining characters
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Subject: Re: CVS changes

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