On Fri, Nov 18, 2011 at 2:47 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Thom Brown <thom@xxxxxxxxx> writes: >>> On 11 November 2011 23:28, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: >>>> I observe that _bt_delitems_vacuum() unconditionally dirties the page >>>> and writes a WAL record, whether it has anything to do or not; and that >>>> if XLogStandbyInfoActive() then btvacuumscan will indeed call it despite >>>> there being (probably) nothing useful to do. Seems like that could be >>>> improved. The comment explaining why it's necessary to do that doesn't >>>> make any sense to me, either. > >>> Well the effect, in the single instances I've checked, is certainly >>> more pronounced for hot_standby, but there still appears to be some >>> occurrences for minimal wal_level too. > >> So would you say this is acceptable and normal activity, or is >> something awry here? > > Well, it's expected given the current coding in the btree vacuum logic. > It's not clear to me why it was written like that, though. The code works as designed. _bt_delitems_vacuum() is only ever called with nitems == 0 when it is the last block of the relation with wal_level = hot standby As discussed in the comments we must issue a WAL record for the last block, whatever else has occurred. So the correct number of WAL records is emitted and I see no bug there. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
