From: | Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Alexander Kumenkov <a(dot)kuzmenkov(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Proposal: Improve bitmap costing for lossy pages |
Date: | 2017-08-31 06:26:50 |
Message-ID: | CAFiTN-ufZ=_3bvdqCnDxKJ13ZsUbjY6swwBF92_8Jyb8znghng@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Wed, Aug 30, 2017 at 2:00 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> I suggest defining a TBM_FILLFACTOR constant instead of repeating the
> value 0.9 in a bunch of places. I think it would also be good to try
> to find the sweet spot for that constant. Making it bigger reduces
> the number of lossy entries created, but making it smaller reduces
> the number of times we have to walk the bitmap. So if, for example,
> 0.75 is sufficient to produce almost all of the gain, then I think we
> would want to prefer 0.75 to 0.9. But if 0.9 is better, then we can
> stick with that.
>
> Note that a value higher than 0.9375 wouldn't be sane without some
> additional safety precautions because maxentries could be as low as
> 16.
Thanks for the feedback. I will work on it.
>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com
From | Date | Subject | |
---|---|---|---|
Next Message | Dilip Kumar | 2017-08-31 06:39:44 | Re: UPDATE of partition key |
Previous Message | Amit Langote | 2017-08-31 06:02:48 | Re: path toward faster partition pruning |