Re: LIKE optimization in UTF-8 and locale-C

Ühel kenal päeval, N, 2007-03-22 kell 11:08, kirjutas Tom Lane:
> ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> > I found LIKE operators are slower on multi-byte encoding databases
> > than single-byte encoding ones. It comes from difference between
> > MatchText() and MBMatchText().
>
> > We've had an optimization for single-byte encodings using
> > pg_database_encoding_max_length() == 1 test. I'll propose to extend it
> > in UTF-8 with locale-C case.
>
> If this works for UTF8, won't it work for all the backend-legal
> encodings?

I guess it works well for % but not for _ , the latter has to know, how
many bytes the current (multibyte) character covers.

The length is still easy to find out for UTF8 encoding, so it may be
feasible to write UTF8MatchText() that is still faster than
MBMatchText().

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