Christopher Browne <cbbro...@gmail.com> writes: > On Thu, Jan 24, 2013 at 5:22 PM, Heikki Linnakangas > <hlinnakan...@vmware.com> wrote: >> Backpatching sounds a bit scary. It's not a clear-cut bug, it's just that >> autovacuum could be smarter about its priorities. There are other ways you >> can still bump into the xid-wraparound issue, even with this patch.
> I don't think this is a single-priority issue. It's *also* crucial > that small tables with high "tuple attrition rates" get vacuumed > extremely frequently; your system will bog down, albeit in a different > way, if the small tables don't get vacuumed enough. Yeah. Another problem with a simple-minded priority arrangement is that it might cause some tables to get starved for service because workers keep on choosing other ones; we have to be sure the sorting rule is designed to prevent that. As posted, what we've got here is sorting on a boolean condition, with the behavior within each group totally up to the whims of qsort(). That seems especially dangerous since the priority order is mostly undefined. I was a bit surprised that Alvaro didn't propose sorting by the age of relfrozenxid, at least for the subset of tables that are considered wraparound hazards. Not sure what a good criterion is for the rest. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers