Re: LIMIT confuses the planner - Mailing list pgsql-performance

From Kouber Saparev
Subject Re: LIMIT confuses the planner
Date
Msg-id 49A2EE86.5070805@saparev.com
Whole thread Raw
In response to Re: LIMIT confuses the planner  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-performance
Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> If you left seq_page_cost (which isn't mentioned here) at the default
>> value but reduced random_page_cost to 0.1, then you have
>> random_page_cost < seq_page_cost.  That's probably Bad.
>
> ... well, it's certainly going to push the planner to believe indexscans
> are cheaper than sorts no matter what.
>
> The previously noted rowcount estimation problem might be a bigger issue
> in this particular case, but I agree this is a Bad Idea.

So I've set it wrong, I guess. :-)

Now I put it to:

seq_page_cost = 1
random_page_cost = 2

Regards,
--
Kouber Saparev
http://kouber.saparev.com

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