Re: Getting query plan alternatives from query planner?

От: Tom Lane
Тема: Re: Getting query plan alternatives from query planner?
Дата: ,
Msg-id: 15381.1395410811@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Getting query plan alternatives from query planner?  (Craig James)
Список: pgsql-performance

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Getting query plan alternatives from query planner?  (Stefan Keller, )
 Re: Getting query plan alternatives from query planner?  (Tom Lane, )
  Re: Getting query plan alternatives from query planner?  (Stefan Keller, )
   Re: Getting query plan alternatives from query planner?  (Atri Sharma, )
    Re: Getting query plan alternatives from query planner?  (Craig James, )
     Re: Getting query plan alternatives from query planner?  (Tom Lane, )
     Re: Getting query plan alternatives from query planner?  (Shaun Thomas, )
      Re: Getting query plan alternatives from query planner?  (Kevin Grittner, )
       Re: Getting query plan alternatives from query planner?  (Eric Schwarzenbach, )
 Re: Getting query plan alternatives from query planner?  (Craig James, )
  Re: Getting query plan alternatives from query planner?  (Stefan Keller, )
   Re: Getting query plan alternatives from query planner?  (Heikki Linnakangas, )

Craig James <> writes:
> There have been many discussions about adding hints to Postgres over the
> years. All have been firmly rejected by the Postgres developers, with
> well-argued reasons.  Search the archives to learn more about this topic.

To clarify: there are good reasons not to like what Oracle calls hints.
On the other hand, the concept of hints that tell the planner what
selectivity or rowcount to expect (as opposed to trying to control the
plan directly) has met with generally more positive reviews.  There's
no specific design yet, and certainly no implementation roadmap, but
I'd not be surprised if we get something like that a few years down
the road.

            regards, tom lane



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