Re: Shouldn't the planner have a higher cost for reverse index scans?

От: Tom Lane
Тема: Re: Shouldn't the planner have a higher cost for reverse index scans?
Дата: ,
Msg-id: 25703.1239383976@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Shouldn't the planner have a higher cost for reverse index scans?  (Josh Berkus)
Ответы: Re: Shouldn't the planner have a higher cost for reverse index scans?  (Josh Berkus)
Re: Shouldn't the planner have a higher cost for reverse index scans?  (Matthew Wakeling)
Список: pgsql-performance

Скрыть дерево обсуждения

Shouldn't the planner have a higher cost for reverse index scans?  (Josh Berkus, )
 Re: Shouldn't the planner have a higher cost for reverse index scans?  (Tom Lane, )
  Re: Shouldn't the planner have a higher cost for reverse index scans?  (Josh Berkus, )
   Re: Shouldn't the planner have a higher cost for reverse index scans?  (Tom Lane, )
    Re: Shouldn't the planner have a higher cost for reverse index scans?  (Josh Berkus, )
     Re: Shouldn't the planner have a higher cost for reverse index scans?  (Lists, )
      Re: Shouldn't the planner have a higher cost for reverse index scans?  (Grzegorz Jaśkiewicz, )
      Re: Shouldn't the planner have a higher cost for reverse index scans?  (Merlin Moncure, )
       Re: Shouldn't the planner have a higher cost for reverse index scans?  (Tom Lane, )
      Re: Shouldn't the planner have a higher cost for reverse index scans?  (Tom Lane, )
       Re: Shouldn't the planner have a higher cost for reverse index scans?  (Lists, )
        Re: Shouldn't the planner have a higher cost for reverse index scans?  (Tom Lane, )
    Re: Shouldn't the planner have a higher cost for reverse index scans?  (Matthew Wakeling, )

Josh Berkus <> writes:
> Not as far as I can tell.   It looks to me like the planner is assuming
> that a forwards index scan and a reverse index scan will have the same
> cost.

Right, because they do.  If you think otherwise, demonstrate it.
(bonnie tests approximating a reverse seqscan are not relevant
to the performance of indexscans.)

            regards, tom lane


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