Re: [HACKERS] choose_bitmap_and again (was Re: Strangely Variable Query Performance)

From: Tom Lane
Subject: Re: [HACKERS] choose_bitmap_and again (was Re: Strangely Variable Query Performance)
Date: ,
Msg-id: 4535.1176565965@sss.pgh.pa.us
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In response to: Re: Strangely Variable Query Performance  (Steve)
List: pgsql-performance

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Slow Postgresql server  (Jason Lustig, )
 Re: Slow Postgresql server  (Dennis Bjorklund, )
 Re: Slow Postgresql server  (Jeff Frost, )
 Re: Slow Postgresql server  (Ron, )
  Re: Slow Postgresql server  (Guido Neitzer, )
   Re: Slow Postgresql server  (Ron, )
    Re: Slow Postgresql server  (Guido Neitzer, )
     Re: Slow Postgresql server  (Scott Marlowe, )
      Re: Slow Postgresql server  (Jeff Frost, )
       Re: Slow Postgresql server  (Carlos Moreno, )
       Strangely Variable Query Performance  (Steve, )
        Re: Strangely Variable Query Performance  (Tom Lane, )
         Re: Strangely Variable Query Performance  (Steve, )
          Re: Strangely Variable Query Performance  (Tom Lane, )
           Re: Strangely Variable Query Performance  (Steve, )
            Re: Strangely Variable Query Performance  (Tom Lane, )
             Re: Strangely Variable Query Performance  (Steve, )
        Re: Strangely Variable Query Performance  (Scott Marlowe, )
         Re: Strangely Variable Query Performance  (Steve, )
          Re: Strangely Variable Query Performance  (Scott Marlowe, )
           Re: Strangely Variable Query Performance  (Steve, )
           Re: Strangely Variable Query Performance  (Tom Lane, )
            Re: Strangely Variable Query Performance  (Steve, )
             Re: Strangely Variable Query Performance  (Tom Lane, )
              Re: Strangely Variable Query Performance  (Steve, )
             Re: Strangely Variable Query Performance  (Tom Lane, )
              Re: Strangely Variable Query Performance  (Steve, )
               Re: Strangely Variable Query Performance  (Tom Lane, )
                Re: Strangely Variable Query Performance  (Steve, )
                 Re: Strangely Variable Query Performance  (Tom Lane, )
                  Re: Strangely Variable Query Performance  (Steve, )
                   Re: Strangely Variable Query Performance  (Tom Lane, )
                   Re: Strangely Variable Query Performance  (Tom Lane, )
                    Re: Strangely Variable Query Performance  (Steve, )
                     Re: Strangely Variable Query Performance  (Tom Lane, )
                      Fwd: Strangely Variable Query Performance  ("Robins Tharakan", )
                     choose_bitmap_and again (was Re: Strangely Variable Query Performance)  (Tom Lane, )
                      Re: [HACKERS] choose_bitmap_and again (was Re: Strangely Variable Query Performance)  (Alvaro Herrera, )
                       Re: [HACKERS] choose_bitmap_and again (was Re: Strangely Variable Query Performance)  (Tom Lane, )
                       Re: [HACKERS] choose_bitmap_and again (was Re: Strangely Variable Query Performance)  (Tom Lane, )
              Re: Strangely Variable Query Performance  (Steve, )
             Re: [HACKERS] choose_bitmap_and again (was Re: Strangely Variable Query Performance)  (Tom Lane, )
 Re: Slow Postgresql server  (Jeff Frost, )
  Re: Slow Postgresql server  (Jason Lustig, )
   Re: Slow Postgresql server  (Guido Neitzer, )
 Fwd: Strangely Variable Query Performance  (Robins, )
  Re: Fwd: Strangely Variable Query Performance  (Tom Lane, )

"Dann Corbit" <> writes:
> Instead of sorting, I suggest the quickselect() algorithm, which is
> O(n).

What for?  Common cases have less than half a dozen entries.  That is
not the place we need to be spending engineering effort --- what we
need to worry about is what's the choice algorithm, not implementation
details.

            regards, tom lane


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