Horton

Re: like/ilike improvements

Zeugswetter Andreas DCP SD <zeugswettera@spardat.at>

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From: "Zeugswetter Andreas ADI SD" <ZeugswetterA@spardat.at>
To: "Tom Lane" <tgl@sss.pgh.pa.us>, "Andrew Dunstan" <andrew@dunslane.net>
Cc: <andrew@supernews.com>, <pgsql-hackers@postgresql.org>
Date: 2007-05-25T08:16:59Z
Lists: pgsql-hackers 
> > However, I have just about convinced myself that we don't need 
> > IsFirstByte for matching "_" for UTF8, either preceded by "%" or
not, 
> > as it should always be true. Can anyone come up with a counter
example?
> 
> You have to be on a first byte before you can meaningfully 
> apply NextChar, and you have to use NextChar or else you 
> don't count characters correctly (eg "__" must match 2 chars 
> not 2 bytes).

Well, for utf8 NextChar could advance to the next char even if the
current byte
position is in the middle of a multibyte char (skip over all 10xxxxxx). 

(Assuming utf16 surrogate pairs are not encoded as 2 x 3bytes, which is
not valid utf8 anyway)   

Andreas