Re: [PERFORM] Hints proposal

От: Zeugswetter Andreas ADI SD
Тема: Re: [PERFORM] Hints proposal
Дата: ,
Msg-id: E1539E0ED7043848906A8FF995BDA579016A0990@m0143.s-mxs.net
(см: обсуждение, исходный текст)
Ответ на: Re: [PERFORM] Hints proposal  (Josh Berkus)
Ответы: Re: [PERFORM] Hints proposal  (Josh Berkus)
Список: pgsql-hackers

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Re: [PERFORM] Hints proposal  (Tom Lane, )
 Re: [PERFORM] Hints proposal  ("Merlin Moncure", )
 Re: [PERFORM] Hints proposal  ("Jim C. Nasby", )
  Re: [PERFORM] Hints proposal  (Tom Lane, )
  Re: [PERFORM] Hints proposal  (Josh Berkus, )
   Re: [PERFORM] Hints proposal  ("Jim C. Nasby", )
    Re: [PERFORM] Hints proposal  (Josh Berkus, )
     Re: [PERFORM] Hints proposal  ("Bucky Jordan", )
      Re: [PERFORM] Hints proposal  (Alvaro Herrera, )
       Re: [PERFORM] Hints proposal  (Jeff Davis, )
        Re: [PERFORM] Hints proposal  ("Bucky Jordan", )
         Re: [PERFORM] Hints proposal  (Jeff Davis, )
          Re: [PERFORM] Hints proposal  ("Jim C. Nasby", )
           Re: [PERFORM] Hints proposal  ("Joshua D. Drake", )
            Re: [PERFORM] Hints proposal  (Andrew Dunstan, )
           Re: [PERFORM] Hints proposal  (David Fetter, )
           Re: [PERFORM] Hints proposal  (Jeff Davis, )
           Re: [PERFORM] Hints proposal  (Stefan Kaltenbrunner, )
     Re: [PERFORM] Hints proposal  ("Jim C. Nasby", )
      Re: [PERFORM] Hints proposal  (Tom Lane, )
      Re: [PERFORM] Hints proposal  ("Bucky Jordan", )
      Re: [PERFORM] Hints proposal  (Josh Berkus, )
       Re: [PERFORM] Hints proposal  ("Jim C. Nasby", )
        Re: [PERFORM] Hints proposal  (Alvaro Herrera, )
        Re: [PERFORM] Hints proposal  (Tom Lane, )
     Re: [PERFORM] Hints proposal  (Gregory Stark, )
      Re: [PERFORM] Hints proposal  (Robert Treat, )
   Re: [PERFORM] Hints proposal  ("Zeugswetter Andreas ADI SD", )
    Re: [PERFORM] Hints proposal  (Josh Berkus, )
  Re: [PERFORM] Hints proposal  (Andrew Sullivan, )
   Re: [PERFORM] Hints proposal  ("Merlin Moncure", )
    Re: [PERFORM] Hints proposal  (Andrew Sullivan, )
   Re: [PERFORM] Hints proposal  ("Zeugswetter Andreas ADI SD", )
    Re: [PERFORM] Hints proposal  (Andrew Sullivan, )
     Re: [PERFORM] Hints proposal  (Csaba Nagy, )
      Re: [PERFORM] Hints proposal  (Josh Berkus, )
     Re: [PERFORM] Hints proposal  ("Zeugswetter Andreas ADI SD", )
 Re: [PERFORM] Hints proposal  (Csaba Nagy, )
  Re: [PERFORM] Hints proposal  (Josh Berkus, )
   Re: [PERFORM] Hints proposal  (Csaba Nagy, )
  Re: [PERFORM] Hints proposal  (Tom Lane, )

> I actually think the way to attack this issue is to discuss the kinds
of errors the planner makes, and what tweaks we could do to correct
them.
> Here's the ones I'm aware of:
>
> -- Incorrect selectivity of WHERE clause
> -- Incorrect selectivity of JOIN
> -- Wrong estimate of rows returned from SRF
> -- Incorrect cost estimate for index use
>
> Can you think of any others?

I think your points are too generic, there is no way to get them all
100% correct from statistical
data even with data hints (and it is usually not at all necessary for
good enough plans).
I think we need to more precisely define the problems of our system with
point in time statistics

-- no reaction to degree of other concurrent activity
-- no way to react to abnormal skew that only persists for a very short
duration
-- too late reaction to changing distribution (e.g. current date column
when a new year starts)
    and the variant: too late adaption when a table is beeing filled
-- missing cost/selectivity estimates for several parts of the system

Andreas


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