| From: | "Vadim B(dot) Mikheev" <vadim(at)sable(dot)krasnoyarsk(dot)su> |
|---|---|
| To: | "Thomas G(dot) Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu> |
| Cc: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>, hackers(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] Re: subselects |
| Date: | 1998-01-12 09:40:48 |
| Message-ID: | 34B9E520.4C0EA6BC@sable.krasnoyarsk.su |
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| Lists: | pgsql-hackers |
Thomas G. Lockhart wrote:
>
> btw, to implement "(a,b,c) OP (d,e,f)" I made a new routine in the parser called
> makeRowExpr() which breaks this up into a sequence of "and" and/or "or" expressions.
> If lists are handled farther back, this routine should move to there also and the
> parser will just pass the lists. Note that some assumptions have to be made about the
> meaning of "(a,b) OP (c,d)", since usually we only have knowledge of the behavior of
> "a OP c". Easy for the standard SQL operators, unknown for others, but maybe it is OK
> to disallow those cases or to look for specific appearance of the operator to guess
> the behavior (e.g. if the operator has "<" or "=" or ">" then build as "and"s and if
> it has "<>" or "!" then build as "or"s.
Sorry, I forgot something: is (a, b) OP (x, y) in standard ?
If not then I suggest to don't implement it at all and allow
(a, b) OP [ANY|ALL] (subselect) only.
Vadim
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