Re: [HACKERS] Operator definitions

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От Bruce Momjian
Тема Re: [HACKERS] Operator definitions
Дата
Msg-id 199909281431.KAA18169@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: [HACKERS] Operator definitions  (Tom Lane <tgl@sss.pgh.pa.us>)
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> Adriaan Joubert <a.joubert@albourne.com> writes:
> > OK, here is a patch to allow both ^ and | as operators, both in operator
> > definitions and expressions. It seems to work for me. Unfortunately the
> > regression tests do not tell me an awful lot, as several of them fail on
> > the Alpha anyway. As I don;t really know what I'm doing, I'd appreciate
> > it if somebody else could check the patch out and let me know whether it
> > is ok.
>
> If you search for, eg, '%', you will find there are several production
> lists that call out all the operators; your patch only caught one of them.
>
> This is a real pain in the neck to maintain, but AFAIK we couldn't
> collapse the productions into a single one using MathOp without losing
> operator precedence info :-(
>
> It might be helpful if gram.y had annotations like "# Here be MathOps"
> so that you could search for the darn things and make sure you had
> adjusted each and every production list whenever you added/deleted one.

OK, I have applied a patch to fix all the operator cases for ^ and |.
This will be in 6.6.

The issue is that we want to specify precedence for the common math
operators, and I needed to be able to specify precedence for '|' so people
could do SELECT 'A' | 'B' | 'C'.


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