Re: Planner hints in Postgresql - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Planner hints in Postgresql
Date
Msg-id 23149.1395077061@sss.pgh.pa.us
Whole thread Raw
In response to Re: Planner hints in Postgresql  (Atri Sharma <atri.jiit@gmail.com>)
Responses Re: Planner hints in Postgresql  (Atri Sharma <atri.jiit@gmail.com>)
List pgsql-hackers
Atri Sharma <atri.jiit@gmail.com> writes:
> On Mon, Mar 17, 2014 at 9:45 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Possibly worth noting is that in past discussions, we've concluded that
>> the most sensible type of hint would not be "use this plan" at all, but
>> "here's what to assume about the selectivity of this WHERE clause".
>> That seems considerably less likely to break than any attempt to directly
>> specify plan details.

> Isnt using a user given value for selectivity a pretty risky situation as
> it can horribly screw up the plan selection?

And forcing a plan to be used *isn't* that?  Please re-read the older
threads, since you evidently have not.
        regards, tom lane



pgsql-hackers by date:

Previous
From: Robert Haas
Date:
Subject: Re: on_exit_reset fails to clear DSM-related exit actions
Next
From: Robert Haas
Date:
Subject: Re: Portability issues in shm_mq