On Mon, Feb 20, 2017 at 6:15 PM, Amit Kapila <amit.kapil...@gmail.com> wrote: > On Mon, Feb 20, 2017 at 7:26 AM, Masahiko Sawada <sawada.m...@gmail.com> > wrote: >> On Fri, Feb 17, 2017 at 3:41 AM, Robert Haas <robertmh...@gmail.com> wrote: >>> On Thu, Feb 16, 2017 at 6:17 AM, Simon Riggs <si...@2ndquadrant.com> wrote: >>>> On 15 February 2017 at 08:07, Masahiko Sawada <sawada.m...@gmail.com> >>>> wrote: >>>>> It's a bug. Attached latest version patch, which passed make check. >>>> >>>> In its current form, I'm not sure this is a good idea. Problems... >>>> >>>> 1. I'm pretty sure the world doesn't need another VACUUM parameter >>>> >>>> I suggest that we use the existing vacuum scale factor/4 to reflect >>>> that indexes are more sensitive to bloat. >>> >>> I do not think it's a good idea to control multiple behaviors with a >>> single GUC. We don't really know that dividing by 4 will be right for >>> everyone, or even for most people. It's better to have another >>> parameter with a sensible default than to hardcode a ratio that might >>> work out poorly for some people. >>> >>>> 2. The current btree vacuum code requires 2 vacuums to fully reuse >>>> half-dead pages. So skipping an index vacuum might mean that second >>>> index scan never happens at all, which would be bad. >>> >>> Maybe. If there are a tiny number of those half-dead pages in a huge >>> index, it probably doesn't matter. Also, I don't think it would never >>> happen, unless the table just never gets any more updates or deletes - >>> but that case could also happen today. It's just a matter of >>> happening less frequently. >> > > Yeah thats right and I am not sure if it is worth to perform a > complete pass to reclaim dead/deleted pages unless we know someway > that there are many such pages. Also, I think we do reclaim the > complete page while allocating a new page in btree. > >> The half-dead pages are never cleaned up if the ratio of pages >> containing garbage is always lower than threshold. >> > > Which threshold are you referring here? >
I meant the new parameter in current patch. Regards, -- Masahiko Sawada NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
