Re: is this a bug or I am blind?

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: pgsql-general(at)postgresql(dot)org
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Mage <mage(at)mage(dot)hu>
Subject: Re: is this a bug or I am blind?
Date: 2005-12-17 18:52:18
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Tom Lane wrote:
> Perhaps the fast-path check is a bad idea, but fixing this is not
> just a matter of removing that. If we subscribe to strcoll's
> worldview then we have to conclude that *text strings are not
> hashable*, because strings that should be "equal" may have different
> hash codes.

By the way, I have always been concerned about the feature of Unicode
that you can write logically equivalent strings using different
code-point sequences. Namely, you often have the option of writing an
accented letter using the "legacy" single codepoint (like in ISO
8859-something) or alternatively using accept plus "base letter" as two
code points. Collating systems should treat them the same, so hashing
the byte values won't work anyway. This is a more extreme case of
"tyty" vs. "tty" because using a proper rendering system, those Unicode
strings should look the same to the naked eye. Therefore, I'm doubtful
that using a binary comparison as tie-breaker is proper behavior.

Peter Eisentraut

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