| From: | "Jim C(dot) Nasby" <jim(at)nasby(dot)net> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-performance <pgsql-performance(at)postgresql(dot)org>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: [PERFORM] Hypothetical suggestions for planner, indexing improvement |
| Date: | 2003-05-07 05:08:01 |
| Message-ID: | 20030507000801.E66185@flake.decibel.org |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers pgsql-performance |
On Tue, May 06, 2003 at 09:45:07AM -0400, Tom Lane wrote:
> "Jim C. Nasby" <jim(at)nasby(dot)net> writes:
> > It would be nice to add support for multi-column IN..
> > WHERE (a, b, c) IN (SELECT a, b, c ...)
>
> RTFM...
As someone pointed out, the documentation says you can't. In this case
the docs are wrong (I've added a note).
> > BTW, does postgresql handle IN and EXISTS differently?
>
> Yes.
>
> > Theoretically if the optimizer was good enough you could transform one
> > to the other and not worry about it.
>
> No. They have different responses to NULLs in the subselect result.
They appear to operate the same... what's different?
--
Jim C. Nasby (aka Decibel!) jim(at)nasby(dot)net
Member: Triangle Fraternity, Sports Car Club of America
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