Re: Performance problems with 9.2.15

От: Johan Fredriksson
Тема: Re: Performance problems with 9.2.15
Дата: ,
Msg-id: 1464593729.16712.2.camel@kth.se
(см: обсуждение, исходный текст)
Ответ на: Re: Performance problems with 9.2.15  (Tom Lane)
Ответы: Re: Performance problems with 9.2.15  (Johan Fredriksson)
Список: pgsql-performance

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Performance problems with 9.2.15  (Johan Fredriksson, )
 Re: Performance problems with 9.2.15  (Tom Lane, )
  Re: Performance problems with 9.2.15  (Johan Fredriksson, )
   Re: Performance problems with 9.2.15  (Steve Crawford, )
  Re: Performance problems with 9.2.15  (Johan Fredriksson, )
   Re: Performance problems with 9.2.15  (Johan Fredriksson, )
    Re: Performance problems with 9.2.15  (Johan Fredriksson, )
     Re: Performance problems with 9.2.15  (Claudio Freire, )
      Re: Performance problems with 9.2.15  ("David G. Johnston", )
       Re: Performance problems with 9.2.15  (Claudio Freire, )
        Re: Performance problems with 9.2.15  (Johan Fredriksson, )
         Re: Performance problems with 9.2.15  (Johan Fredriksson, )
          Re: Performance problems with 9.2.15  (Mark Kirkwood, )
           Re: Performance problems with 9.2.15  (Johan Fredriksson, )

> > I am just about to upgrade from PostgreSQL 8.4.20 to 9.2.15, but I'v run
> > into some huge performance issues.
>
> The rowcount estimates from 9.2 seem greatly different from the 8.4 plan.
> Did you remember to ANALYZE all the tables after migrating?  Maybe there
> were some table-specific statistics targets that you forgot to transfer
> over?  In any case, the 9.2 plan looks like garbage-in-garbage-out to
> me :-( ... without estimates at least a little closer to reality, the
> planner is unlikely to do anything very sane.
>
> (BTW, I wonder why you are moving only to 9.2 and not something more
> recent.)

You put me on the right track with your conclusion that the estimates
were off the chart. The quick-and-dirty fix "DELETE FROM pg_statistic;"
solved this problem. This database now have to build up sane estimates
from scratch.


        / Eskil





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