| From: | "Thomas G(dot) Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu> |
|---|---|
| To: | "Vadim B(dot) Mikheev" <vadim(at)sable(dot)krasnoyarsk(dot)su> |
| Cc: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>, hackers(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] Re: subselects |
| Date: | 1998-01-13 15:24:30 |
| Message-ID: | 34BB872E.BF36DF94@alumni.caltech.edu |
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| Thread: | |
| Lists: | pgsql-hackers |
> > > > 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.
>
> Could we restrict OPs to standard ones (like we do for subselects) - I don't
> like assumption about ORs for operators with "!" ?
> "Assume as little as possible" is good rule...
Yes, I agree. The suggestion about "!" was made without thinking very hard just to raise the
possibility. Extending to other operators in a reliable way is an interesting problem, but is
not required and can be explicitly disallowed for now.
- Tom
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