On 20 February 2017 at 09:15, 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.
>>>> 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. Agreed.... which is why On 16 February 2017 at 11:17, Simon Riggs <si...@2ndquadrant.com> wrote: > I suggest that we store the number of half-dead pages in the metapage > after each VACUUM, so we can decide whether to skip the scan or not. > Also, I think we do reclaim the > complete page while allocating a new page in btree. That's not how it works according to the README at least. You might be referring to cleaning out killed tuples just before a page split? That's something different. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
