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Re: Hash join on int takes 8..114 seconds

От: Tom Lane
Тема: Re: Hash join on int takes 8..114 seconds
Дата: ,
Msg-id: 11835.1227298022@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Hash join on int takes 8..114 seconds  (PFC)
Ответы: Re: Hash join on int takes 8..114 seconds  (PFC)
Список: pgsql-performance

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Hash join on int takes 8..114 seconds  ("Andrus", )
 Re: Hash join on int takes 8..114 seconds  (PFC, )
  Re: Hash join on int takes 8..114 seconds  ("Andrus", )
 Re: Hash join on int takes 8..114 seconds  (Richard Huxton, )
  Re: Hash join on int takes 8..114 seconds  ("Andrus", )
   Re: Hash join on int takes 8..114 seconds  (Richard Huxton, )
    Re: Hash join on int takes 8..114 seconds  ("Andrus", )
   Re: Hash join on int takes 8..114 seconds  (PFC, )
    Re: Hash join on int takes 8..114 seconds  ("Andrus", )
     Re: Hash join on int takes 8..114 seconds  (, )
      Re: Hash join on int takes 8..114 seconds  ("Andrus", )
       Re: Hash join on int takes 8..114 seconds  (PFC, )
       Re: Hash join on int takes 8..114 seconds  (Alan Hodgson, )
       Re: Hash join on int takes 8..114 seconds  (Tomas Vondra, )
     Re: Hash join on int takes 8..114 seconds  (Richard Huxton, )
      Re: Hash join on int takes 8..114 seconds  ("Andrus", )
       Re: Hash join on int takes 8..114 seconds  (PFC, )
        Re: Hash join on int takes 8..114 seconds  ("Andrus", )
         Re: Hash join on int takes 8..114 seconds  (Alvaro Herrera, )
          Re: Hash join on int takes 8..114 seconds  ("Andrus", )
           Re: Hash join on int takes 8..114 seconds  (Alvaro Herrera, )
            Re: Hash join on int takes 8..114 seconds  ("Andrus", )
             Re: Hash join on int takes 8..114 seconds  (Alvaro Herrera, )
           Re: Hash join on int takes 8..114 seconds  (Tomas Vondra, )
      Re: Hash join on int takes 8..114 seconds  ("Andrus", )
       Re: Hash join on int takes 8..114 seconds  (Scott Carey, )
     Re: Hash join on int takes 8..114 seconds  (PFC, )
      Re: Hash join on int takes 8..114 seconds  (Tom Lane, )
       Re: Hash join on int takes 8..114 seconds  (PFC, )
      Re: Hash join on int takes 8..114 seconds  ("Andrus", )
       Re: Hash join on int takes 8..114 seconds  (PFC, )
        Re: Hash join on int takes 8..114 seconds  ("Andrus", )
         Re: Hash join on int takes 8..114 seconds  (Tomas Vondra, )
          Re: Hash join on int takes 8..114 seconds  ("Andrus", )
           Re: Hash join on int takes 8..114 seconds  (Tomas Vondra, )
         Re: Hash join on int takes 8..114 seconds  (Scott Carey, )
          Re: Hash join on int takes 8..114 seconds  ("Andrus", )
           Re: Hash join on int takes 8..114 seconds  (Tomas Vondra, )
            Re: Hash join on int takes 8..114 seconds  ("Andrus", )
             Re: Hash join on int takes 8..114 seconds  (, )
              Re: Hash join on int takes 8..114 seconds  ("Andrus", ) 
PFC <> writes:
> Index on orders_products( product_id ) and orders_products( order_id ):
>     => Same plan

>     Note that in this case, a smarter planner would use the new index to
> perform a BitmapAnd before hitting the heap to get the rows.

Considering that the query has no constraint on
orders_products.order_id, I'm not sure what you think the extra index is
supposed to be used *for*.

(Well, we could put orders as the outside of a nestloop and then we'd
have such a constraint, but with 30000 orders rows to process that plan
would lose big.)

(And yes, the planner did consider such a plan along the way.
See choose_bitmap_and.)

            regards, tom lane

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