Re: [HACKERS] EXISTS optimization

От: Martijn van Oosterhout
Тема: Re: [HACKERS] EXISTS optimization
Дата: ,
Msg-id: 20070324130759.GA1089@svana.org
(см: обсуждение, исходный текст)
Ответ на: Re: [HACKERS] EXISTS optimization  ("Kevin Grittner")
Список: pgsql-performance

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EXISTS optimization  ("Kevin Grittner", )
 Re: [HACKERS] EXISTS optimization  (Tom Lane, )
  Re: [HACKERS] EXISTS optimization  ("Kevin Grittner", )
   Re: [HACKERS] EXISTS optimization  ("Kevin Grittner", )
   Re: [HACKERS] EXISTS optimization  (Tom Lane, )
  Re: [HACKERS] EXISTS optimization  (Martijn van Oosterhout, )
   Re: [HACKERS] EXISTS optimization  ("Kevin Grittner", )
    Re: [HACKERS] EXISTS optimization  (Martijn van Oosterhout, )
 Re: [HACKERS] EXISTS optimization  ("Kevin Grittner", )
  Re: [HACKERS] EXISTS optimization  ("Craig A. James", )

On Fri, Mar 23, 2007 at 05:30:27PM -0500, Kevin Grittner wrote:
> I don't understand -- TRUE OR UNKNOWN evaluates to TRUE, so why would
> the IN need to continue?  I'm not quite following the rest; could you
> elaborate or give an example?  (Sorry if I'm lagging behind the rest
> of the class here.)

You're right, I'm getting confused with the interaction of NULL and NOT
IN.

The multiple evaluation thing still applies, but that's minor.

Have a nice day,
--
Martijn van Oosterhout   <>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.


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