Re: query plan question, nested loop vs hash join
| От | Andrey Lizenko |
|---|---|
| Тема | Re: query plan question, nested loop vs hash join |
| Дата | |
| Msg-id | CADKuZZA-92M7h6YwGwV-HUSZ2eO8tYV9CYFA0ZC=0z6By3KqbQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: query plan question, nested loop vs hash join (Marti Raudsepp <marti@juffo.org>) |
| Список | pgsql-performance |
Thanks for your reply, Marti, as I answered to Tom couple of days ago adjusting of 'effective_cache_size' to 80% of RAM and 'random_page_cost' from 2 to 1 helped me.
On 8 October 2014 00:26, Marti Raudsepp <marti@juffo.org> wrote:
On Fri, Oct 3, 2014 at 6:38 PM, Andrey Lizenko <lizenko79@gmail.com> wrote:
> Is it possible to force optimizer choose the second plan without doing "set
> enable_hashjoin = off;" ?
>
> Increasing of 'effective_cache_size' leads to similar thing with mergejoin,
> other options (work_mem, shared_buffers. etc) do not change anything.
Have you tried changing random_page_cost?
In small databases where most of the data is cached anyway, lowering
random_page_cost to somewhere between 1 and 2 usually leads to better
planner decisions.
Regards,
Marti
С уважением, Андрей Лизенко
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