Re: [HACKERS] Re: subselects

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От Vadim B. Mikheev
Тема Re: [HACKERS] Re: subselects
Дата
Msg-id 34B9E520.4C0EA6BC@sable.krasnoyarsk.su
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Ответ на Re: subselects  (Bruce Momjian <maillist@candle.pha.pa.us>)
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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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