Tom Lane <tgl@sss.pgh.pa.us> wrote:
> On the strength of this closer reading, I would say that the patch isn't
> relying on UTF8's first-byte-vs-not-first-byte property after all.
> All that it's relying on is that no MB character is a prefix of another
> one, which seems like a necessary property for any sane encoding; plus
> that characters are considered equal only if they're bytewise equal.
> So are we sure it doesn't work for non-UTF8 encodings? Maybe that
> earlier conclusion was based on a misunderstanding of what the patch
> really does.
Yes, I only used the 'disjoint representations for first-bytes and
not-first-bytes of MB characters' feature in UTF8. Other encodings
allows both [AB] and [BA] for MB character patterns. UTF8Match() does
not cope with those encodings; If we have '[AB][AB]' in a table and
search it with LIKE '%[BA]%', we judge that they are matched by mistake.
I've also misunderstood it before, and Dennis Bjorklund pointed out.
http://archives.postgresql.org/pgsql-hackers/2007-03/msg01377.php
Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center
