Re: Any better plan for this query?..

From: Ries van Twisk
Subject: Re: Any better plan for this query?..
Date: ,
Msg-id: 3D84DC40-FD91-4CC3-85F7-9F5B1FCF5D89@rvt.dds.nl
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In response to: Re: Any better plan for this query?..  (Richard Huxton)
Responses: Re: Any better plan for this query?..  (Dimitri)
List: pgsql-performance

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Any better plan for this query?..  (Dimitri, )
 Re: Any better plan for this query?..  (Craig Ringer, )
  Re: Any better plan for this query?..  (Dimitri, )
   Re: Any better plan for this query?..  (Chris, )
    Re: Any better plan for this query?..  (Dimitri, )
     Re: Any better plan for this query?..  (Richard Huxton, )
     Re: Any better plan for this query?..  (Craig Ringer, )
      Re: Any better plan for this query?..  (Kenneth Marshall, )
       Re: Any better plan for this query?..  (Matthew Wakeling, )
      Re: Any better plan for this query?..  (Dimitri, )
  Re: Any better plan for this query?..  (Kenneth Marshall, )
 Re: Any better plan for this query?..  (Heikki Linnakangas, )
  Re: Any better plan for this query?..  (Dimitri, )
   Re: Any better plan for this query?..  (Simon Riggs, )
    Re: Any better plan for this query?..  (Dimitri, )
     Re: Any better plan for this query?..  (Merlin Moncure, )
      Re: Any better plan for this query?..  (Dimitri, )
       Re: Any better plan for this query?..  (Simon Riggs, )
        Re: Any better plan for this query?..  (Dimitri, )
         Re: Any better plan for this query?..  (Tom Lane, )
          Re: Any better plan for this query?..  (Dimitri, )
          Re: Any better plan for this query?..  (Simon Riggs, )
         Re: Any better plan for this query?..  (Merlin Moncure, )
         Re: Any better plan for this query?..  (Simon Riggs, )
          Re: Any better plan for this query?..  (Dimitri, )
         Re: Any better plan for this query?..  (Aidan Van Dyk, )
          Re: Any better plan for this query?..  (Dimitri, )
           Re: Any better plan for this query?..  (Alvaro Herrera, )
            Re: Any better plan for this query?..  (Dimitri, )
             Re: Any better plan for this query?..  (Dimitri Fontaine, )
              Re: Any better plan for this query?..  (Dimitri, )
               Re: Any better plan for this query?..  (Simon Riggs, )
                Re: Any better plan for this query?..  (Dimitri, )
                 Re: Any better plan for this query?..  (Simon Riggs, )
               Re: Any better plan for this query?..  (Heikki Linnakangas, )
                Re: Any better plan for this query?..  (Dimitri, )
                 Re: Any better plan for this query?..  (Simon Riggs, )
                  Re: Any better plan for this query?..  (Dimitri, )
                   Re: Any better plan for this query?..  (Simon Riggs, )
                    Re: Any better plan for this query?..  (Dimitri, )
                     Re: Any better plan for this query?..  (Simon Riggs, )
                      Re: Any better plan for this query?..  ("Dave Dutcher", )
                       Re: Any better plan for this query?..  (Dimitri, )
                        Re: Any better plan for this query?..  (Merlin Moncure, )
                         Re: Any better plan for this query?..  (Dimitri, )
                          Re: Any better plan for this query?..  (Merlin Moncure, )
                           Re: Any better plan for this query?..  (Dimitri, )
                            Re: Any better plan for this query?..  (Merlin Moncure, )
                      Re: Any better plan for this query?..  (Dimitri, )
                       Re: Any better plan for this query?..  (Simon Riggs, )
                        Re: Any better plan for this query?..  (Dimitri, )
                         Re: Any better plan for this query?..  (Dimitri, )
                          Re: Any better plan for this query?..  (Simon Riggs, )
                           Re: Any better plan for this query?..  (Dimitri, )
                      Re: Any better plan for this query?..  (Tom Lane, )
                       Re: Any better plan for this query?..  (Dimitri, )
                       Re: Any better plan for this query?..  (Simon Riggs, )
                        Re: Any better plan for this query?..  (Matthew Wakeling, )
                         Re: Any better plan for this query?..  (Simon Riggs, )
                          Re: Any better plan for this query?..  (Simon Riggs, )
                          Re: Any better plan for this query?..  (Matthew Wakeling, )
                           Re: Any better plan for this query?..  (Simon Riggs, )
                           Re: Any better plan for this query?..  (Scott Carey, )
                          Re: Any better plan for this query?..  (Robert Haas, )
                        Re: Any better plan for this query?..  (Tom Lane, )
                         Re: Any better plan for this query?..  (Simon Riggs, )
                          Re: Any better plan for this query?..  (Tom Lane, )
                           Re: Any better plan for this query?..  (Robert Haas, )
                            Re: Any better plan for this query?..  (Simon Riggs, )
                             Re: Any better plan for this query?..  (Robert Haas, )
                              Re: Any better plan for this query?..  (Simon Riggs, )
                     Re: Any better plan for this query?..  (Scott Carey, )
                      Re: Any better plan for this query?..  (Dimitri, )
                       Re: Any better plan for this query?..  (Scott Carey, )
                        Re: Any better plan for this query?..  (Dimitri, )
                         Re: Any better plan for this query?..  (Scott Carey, )
                          Re: Any better plan for this query?..  (Dimitri, )
               Re: Any better plan for this query?..  (Simon Riggs, )
                Re: Any better plan for this query?..  (Dimitri, )
                 Re: Any better plan for this query?..  (Robert Haas, )
                  Re: Any better plan for this query?..  (Dimitri, )
                   Re: Any better plan for this query?..  ("Kevin Grittner", )
                   Re: Any better plan for this query?..  ("Joshua D. Drake", )
                    Re: Any better plan for this query?..  (Dimitri, )
                   Re: Any better plan for this query?..  (Robert Haas, )
                    Re: Any better plan for this query?..  (Dimitri, )
               Re: Any better plan for this query?..  (Stefan Kaltenbrunner, )
                Re: Any better plan for this query?..  (Dimitri, )
                 Re: Any better plan for this query?..  (Stefan Kaltenbrunner, )
                  Re: Any better plan for this query?..  (Matthew Wakeling, )
                   Re: Any better plan for this query?..  (Simon Riggs, )
                    Re: Any better plan for this query?..  (Matthew Wakeling, )
                     Re: Any better plan for this query?..  (Stefan Kaltenbrunner, )
                     Re: Any better plan for this query?..  (Tom Lane, )
                      Re: Any better plan for this query?..  (Robert Haas, )
                  Re: Any better plan for this query?..  (Dimitri, )
   Re: Any better plan for this query?..  ("Joshua D. Drake", )
           Re: Any better plan for this query?..  (Heikki Linnakangas, )
            Re: Any better plan for this query?..  (Dimitri, )
           Re: Any better plan for this query?..  (Andres Freund, )
            Re: Any better plan for this query?..  (Alvaro Herrera, )
             Re: Any better plan for this query?..  (Scott Carey, )
              Re: Any better plan for this query?..  (Dimitri, )
               Re: Any better plan for this query?..  (Scott Carey, )
                Re: Any better plan for this query?..  (Dimitri Fontaine, )
                 Re: Any better plan for this query?..  (Dimitri, )
                 Re: Any better plan for this query?..  (Simon Riggs, )
                Re: Any better plan for this query?..  (Dimitri, )
    Re: Any better plan for this query?..  (Gregory Stark, )
     Re: Any better plan for this query?..  (Simon Riggs, )
  Re: Any better plan for this query?..  (Matthew Wakeling, )
  Re: Any better plan for this query?..  (Tom Lane, )
   Re: Any better plan for this query?..  (Greg Stark, )
   Re: Any better plan for this query?..  (Robert Haas, )
  Re: Any better plan for this query?..  (Simon Riggs, )
   Re: Any better plan for this query?..  ("Joshua D. Drake", )
    Re: Any better plan for this query?..  (Aidan Van Dyk, )
     Re: Any better plan for this query?..  (Stephen Frost, )
   Re: Any better plan for this query?..  (Robert Haas, )
   Re: Any better plan for this query?..  (Glenn Maynard, )
    Re: Any better plan for this query?..  (Dimitri, )
    Re: Any better plan for this query?..  ("Kevin Grittner", )
     Re: Any better plan for this query?..  (Dimitri, )
      Re: Any better plan for this query?..  ("Kevin Grittner", )
  Re: Any better plan for this query?..  (Dimitri Fontaine, )
   Re: Any better plan for this query?..  (Alvaro Herrera, )
  Re: Any better plan for this query?..  (Robert Haas, )
   Re: Any better plan for this query?..  (Dimitri, )
 Re: Any better plan for this query?..  (Dimitri, )
  Re: Any better plan for this query?..  (Richard Huxton, )
  Re: Any better plan for this query?..  ("Albe Laurenz", )
   Re: Any better plan for this query?..  (Dimitri, )
    Re: Any better plan for this query?..  (Kenneth Marshall, )
 Re: Any better plan for this query?..  (Merlin Moncure, )
  Re: Any better plan for this query?..  (Merlin Moncure, )
   Re: Any better plan for this query?..  (Dimitri, )
    Re: Any better plan for this query?..  (Richard Huxton, )
     Re: Any better plan for this query?..  (Ries van Twisk, )
      Re: Any better plan for this query?..  (Dimitri, )
 Re: Any better plan for this query?..  (Kenneth Marshall, )
  Re: Any better plan for this query?..  (Dimitri, )
   Re: Any better plan for this query?..  (Kenneth Marshall, )
 Re: Any better plan for this query?..  (Dimitri, )
  Re: Any better plan for this query?..  (Alvaro Herrera, )
 Re: Any better plan for this query?..  (Simon Riggs, )

On May 6, 2009, at 7:53 AM, Richard Huxton wrote:

> Dimitri wrote:
>> I'll try to answer all mails at once :-))
>> - query is running fully in RAM, no I/O, no network, only CPU time
>> - looping 100 times the same query gives 132ms total time (~1.32ms
>> per
>> query), while it's 44ms on InnoDB (~0.44ms per query)
>
> Well, assuming you're happy that PG is tuned reasonably for your
> machine and that MySQL's query cache isn't returning the results
> here it looks like MySQL is faster for this particular query.
>
> The only obvious place there could be a big gain is with the hashing
> algorithm. If you remove the ORDER BY and the query-time doesn't
> fall by much then it's the hash phase.
>
> The other thing to try is to alter the query to be a SELECT count(*)
> rather than returning rows - that will let you measure the time to
> transfer the result rows.
>
> --
>  Richard Huxton
>  Archonet Ltd
>


Do you expect to run this query 100 times per second during your
application?
or is this just a test to see how fast the query is for optimalisation.

I always get scared myself with such a test as 'runs out of memory',
reason
given is that usually this is not really the case in a production
environment.

Try to make a little test case where you give the query random
parameters
so different result sets are returned. This will give you a better
idea on how
fast the query really is and might give you better comparison results.

instead of count(*) I isusallt do explain analyze to see how fast
PostgreSQL handles to query.

Ries




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From: Kenneth Marshall
Date:
Subject: Re: Any better plan for this query?..
From: Simon Riggs
Date:
Subject: Re: Transparent table partitioning in future version of PG?