AW: Yet another LIKE-indexing scheme

From: Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at>
To: "'Jules Bean'" <jules(at)jellybean(dot)co(dot)uk>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: AW: Yet another LIKE-indexing scheme
Date: 2000-09-06 15:19:46
Message-ID: 11C1E6749A55D411A9670001FA687963368069@sdexcsrv1.f000.d0188.sd.spardat.at
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> On Sat, Sep 02, 2000 at 01:39:47PM -0400, Tom Lane wrote:
> > > So what happens with "WHERE name like 'Czec%`" ?
> >
> > Our existing code fails because it generates WHERE name >=
> 'Czec' AND
> > name < 'Czed'; it will therefore not find names beginning 'Czech'
> > because those are in another part of the index, between 'Czeh' and
> > 'Czei'. But WHERE name >= 'Cze' AND name < 'Czf' would work.
>
> (OK, I haven't read the previous discussion. Guilty, m'lud)
>
> Why should it? If 'ch' is one letter, then surely 'czech' isn't LIKE
> 'czec%'. Because 'czec%' has a second c, wheres, 'czech' only has one
> 'c' and one 'ch'?

Indeed an interesting interpretation, but what I guess makes it bogus is
that
words can exist that have a h after the c that do not represent the ch
character.

Andreas

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