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Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)

От: a3a18850@telus.net
Тема: Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)
Дата: ,
Msg-id: 1112920211.4255d0934e23d@webmail.telus.net
(см: обсуждение, исходный текст)
Ответ на: Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Tom Lane)
Список: pgsql-performance

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Plan for relatively simple query seems to be very inefficient  (Arjen van der Meijden, )
 Re: Plan for relatively simple query seems to be very inefficient  (Steve Atkins, )
  Re: Plan for relatively simple query seems to be very inefficient  (Arjen van der Meijden, )
 Re: Plan for relatively simple query seems to be very inefficient  (Tom Lane, )
  Re: Plan for relatively simple query seems to be very inefficient  (Arjen van der Meijden, )
   Re: Plan for relatively simple query seems to be very inefficient  (Tom Lane, )
    Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Tom Lane, )
     Re: [HACKERS] Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  ("Jim C. Nasby", )
      Re: [HACKERS] Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Tom Lane, )
       Re: [HACKERS] Recognizing range constraints (was Re: Plan  (John A Meinel, )
        Re: [HACKERS] Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Tom Lane, )
       Re: [HACKERS] Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  ("Jim C. Nasby", )
     Re: Recognizing range constraints (was Re: Plan for  (Simon Riggs, )
     Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Bruno Wolff III, )
      Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Tom Lane, )
       Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Mischa, )
        Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (Tom Lane, )
         Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)  (, )
 Re: Plan for relatively simple query seems to be very inefficient  ("Dave Held", )
  Re: Plan for relatively simple query seems to be very inefficient  (Tom Lane, )
  Re: Plan for relatively simple query seems to be very inefficient  (Tom Lane, )
 Re: Plan for relatively simple query seems to be very inefficient  (Mischa, ) 
Quoting Tom Lane <>:

> Mischa <> writes:
> > Quoting Tom Lane <>:
> >> WHERE a.x > b.y AND a.x < 42
>
> > Out of curiosity, will the planner induce "b.y < 42" out of this?
>
> No.  There's some smarts about transitive equality, but none about
> transitive inequalities.  Offhand I'm not sure if it'd be useful to add
> such.  The transitive-equality code pulls its weight [...]
> but I'm less able to think of common use-cases for transitive
> inequality ...

Thanks. My apologies for not just going and looking at the code first.

Equality-transitives: yes, worth their weight in gold.
Inequality-transitivies: I see in OLAP queries (usually ranges), or in queries
against big UNION ALL views, where const false inequalities are the norm.
"a.x > b.y and a.x < c.z" comes up in OLAP, too, usually inside an EXISTS(...),
where you are doing something analogous to finding a path.

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