Re: like/ilike improvements

Tom Lane wrote:
> Yeah. It seems we need three comparison functions after all:
>

Yeah, that was my confusion. I thought we had concluded that we didn't,
but clearly we do.

> 1. Single-byte character set: needs NextByte and ByteEq only.
>
> 2. Generic multi-byte character set: both % and _ must advance by
> characters to ensure we never try an out-of-alignment character
> comparison. But simple character comparison works bytewise given
> that. So primitives are NextChar, NextByte, ByteEq.
>
> 3. UTF8: % can advance bytewise. _ must check it is on a first byte
> (else return match failure) and if so do NextChar. So primitives
> are NextChar, NextByte, ByteEq, IsFirstByte.
>
> In no case do we need CharEq. I'd be inclined to drop ByteEq as a
> macro and just use "==", too.
>
>
>

I'll work this up. I think it will be easier if I marry cases 1 and 2,
with NextChar being the same as NextByte in the single byte case.

cheers

andrew