Re: Major differences between oracle and postgres performance - what can I do ?

От: Tom Lane
Тема: Re: Major differences between oracle and postgres performance - what can I do ?
Дата: ,
Msg-id: 22514.1087578111@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost)
Ответы: Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost)
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Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )
 Re: Major differences between oracle and postgres performance  (Richard Huxton, )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Paul Thomas, )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Jeff, )
 Re: Major differences between oracle and postgres performance  (Shridhar Daithankar, )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )
  Re: Major differences between oracle and postgres performance  (pginfo, )
  Re: Major differences between oracle and postgres performance  (Richard Huxton, )
  Re: Major differences between oracle and postgres performance - what can I do ?  (Tom Lane, )
   Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost, )
    Re: Major differences between oracle and postgres performance - what can I do ?  (Tom Lane, )
     Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost, )
      Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost, )
  Re: Major differences between oracle and postgres performance  (pginfo, )
  Re: Major differences between oracle and postgres performance - what can I do ?  ("Mischa Sandberg", )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )
  Re: Major differences between oracle and postgres performance - what can I do ?  (Tom Lane, )
   Re: Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )

Stephen Frost <> writes:
> * Tom Lane () wrote:
>> [... thinks for awhile ...]  It seems possible that they may use sort
>> code that knows it is performing a DISTINCT operation and discards
>> duplicates on sight.  Given that there are only 534 distinct values,
>> the sort would easily stay in memory if that were happening.

> Could this optimization be added to PostgreSQL?  It sounds like a very
> reasonable thing to do.

That's what I was wondering about too.  But first I'd like to get
some kind of reading on how effective it would be.  If someone can
demonstrate that Oracle can do sort-and-drop-dups a lot faster than
it can do a straight sort of the same amount of input data, that
would be a strong indication that it's worth doing.  At this point
we don't know if that's the source of their win or not.

            regards, tom lane


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