Re: A questions on planner choices

On Fri, Aug 19, 2011 at 1:05 PM, Edoardo Panfili <edoardo(at)aspix(dot)it> wrote:
> [1] Plan for the firts query
> -------------------------------------------------------------------------------------------------------------------------------------------------------
>  Sort  (cost=20.45..20.46 rows=1 width=931) (actual time=4457.775..4457.786
> rows=76 loops=1)
>   Sort Key: cartellino.id
>   Sort Method:  quicksort  Memory: 74kB
>   ->  Hash Join  (cost=8.32..20.44 rows=1 width=931) (actual
> time=243.679..4457.658 rows=76 loops=1)
>         Hash Cond: (cartellino.idspecie = principale.id)
>         ->  Nested Loop  (cost=0.00..9.81 rows=614 width=886) (actual
> time=4.094..4439.024 rows=18370 loops=1)

The row estimate here is off by a factor of 30 or so. In this case a
different join method would likely work better. It might be that
cranking up stats for the columns involved will help, but if that
doesn't change the estimates then we might need to look elsewhere.

What's your work_mem and random_page_cost?