Re: Simple join optimized badly?

От: Mark Kirkwood
Тема: Re: Simple join optimized badly?
Дата: ,
Msg-id: 4529C43A.3050503@paradise.net.nz
(см: обсуждение, исходный текст)
Ответ на: Re: Simple join optimized badly?  ("Craig A. James")
Ответы: Re: Simple join optimized badly?  (Tom Lane)
Список: pgsql-performance

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Simple join optimized badly?  ("Craig A. James", )
 Re: Simple join optimized badly?  (Tom Lane, )
  Re: Simple join optimized badly?  ("Denis Lussier", )
   Re: Simple join optimized badly?  (Jim Nasby, )
   Re: Simple join optimized badly?  (Josh Berkus, )
    Re: Simple join optimized badly?  ("Craig A. James", )
     Re: Simple join optimized badly?  (Mark Kirkwood, )
      Re: Simple join optimized badly?  ("Craig A. James", )
       Re: Simple join optimized badly?  (Mark Kirkwood, )
        Re: Simple join optimized badly?  (Tom Lane, )
         Re: Simple join optimized badly?  (Josh Berkus, )
          Re: Simple join optimized badly?  (Tom Lane, )
    Re: Simple join optimized badly?  (Tom Lane, )
    Re: Simple join optimized badly?  (Scott Marlowe, )
 Re: Simple join optimized badly?  (Bruce Momjian, )
  Re: Simple join optimized badly?  ("Craig A. James", )
 Re: Simple join optimized badly?  (Chris Browne, )
 Re: Simple join optimized badly?  (Chris Browne, )
  Re: Simple join optimized badly?  ("Jim C. Nasby", )
   Re: Simple join optimized badly?  (Tom Lane, )
   Re: Simple join optimized badly?  (Mark Kirkwood, )
    Re: Simple join optimized badly?  (Mark Kirkwood, )
 Re: Simple join optimized badly?  (Tobias Brox, )
  Re: Simple join optimized badly?  ("Jim C. Nasby", )
   Re: Simple join optimized badly?  ("Joshua D. Drake", )
    Re: Simple join optimized badly?  ("Jim C. Nasby", )
     Re: Simple join optimized badly?  ("Joshua D. Drake", )
   Re: Simple join optimized badly?  (Tom Lane, )
    Re: Simple join optimized badly?  ("Jim C. Nasby", )
     Re: Simple join optimized badly?  (Tom Lane, )
      Re: Simple join optimized badly?  ("Jim C. Nasby", )
       Re: Simple join optimized badly?  (Josh Berkus, )
        Re: Simple join optimized badly?  ("Jim C. Nasby", )
  Re: Simple join optimized badly?  (Bruno Wolff III, )
 Re: Simple join optimized badly?  (Brian Herlihy, )
  Re: Simple join optimized badly?  ("Craig A. James", )
   Re: Simple join optimized badly?  ("Joshua D. Drake", )
    Re: Simple join optimized badly?  ("Jim C. Nasby", )
     Re: Simple join optimized badly?  ("Steinar H. Gunderson", )
      Re: Simple join optimized badly?  ("Joshua D. Drake", )
     Re: Simple join optimized badly?  ("Joshua D. Drake", )
      Re: Simple join optimized badly?  (Brian Herlihy, )
       Re: Simple join optimized badly?  (Tom Lane, )
        Re: Simple join optimized badly?  (Brian Herlihy, )
        Re: Simple join optimized badly?  ("Bucky Jordan", )
         Re: Simple join optimized badly?  (Heikki Linnakangas, )
          Re: Simple join optimized badly?  (Bruce Momjian, )
         Collect stats during seqscan (was: Simple join optimized badly?)  ("Jim C. Nasby", )
        Re: Simple join optimized badly?  (Mark Lewis, )

Craig A. James wrote:

>
> Perhaps you scanned past what I wrote a couple paragraphs farther down.
> I'm going to repeat it because it's the KEY POINT I'm trying to make:
>
> Craig James wrote:
>> Now you might argue that function-cost needs to be added to the
>> optimizer's arsenal of tricks.  And I'd agree with you: That WOULD be
>> a better solution than hints.  But I need my problem solved TODAY, not
>> next year.  Hints can help solve problems NOW that can be brought to
>> the PG team's attention later, and in the mean time let me get my
>> application to work.

True enough - but (aside from the fact that hints might take just as
long to get into the development tree as cost-for-functions might take
to write and put in...) there is a nasty side effect to adding hints -
most of the raw material for optimizer improvement disappears (and hence
optimizer improvement stalls)- why? simply that everyone then hints
everything - welcome to the mess that Oracle are in (and seem to be
trying to get out of recently)!

I understand that it is frustrating to not have the feature you need now
  - but you could perhaps view it as a necessary part of the community
development process - your need is the driver for optimizer improvement,
and it can take time.

Now ISTM that hints "solve" the problem by removing the need any further
optimizer improvement at all - by making *you* the optimizer. This is
bad for those of us in the DSS world, where most ad-hoc tools do not
provide the ability to add hints.

Cheers

Mark





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