Jim C. Nasby wrote:
On Tue, Feb 27, 2007 at 12:00:41AM -0300, Alvaro Herrera wrote:
Jim C. Nasby wrote:
The advantage to keying this to autovac_naptime is that it means we
don't need another GUC, but after I suggested that before I realized
that's probably not the best idea. For example, I've seen clusters that
are running dozens-hundreds of databases; in that environment you really
need to turn naptime way down (to like a second). In that case you
wouldn't want to key to naptime.
Actually, I've been thinking that it would be a good idea to change the
semantics of autovacuum_naptime so that it means the average time to
start a worker in any given database. That way, the time between
autovac runs is not dependent on the number of databases you have.
BTW, another issue that I don't think we can ignore: we actually need to
do this on a per-tablespace level, or at least have the ability to
disable or somehow limit it. While it's not common, there are users that
run a hundred or more databases in a single cluster; it would be ugly if
we suddenly had 100 vacuums trying to run on the same set of drives
concurrently.
I think we all agree that autovacuum needs to become tablespace aware at
some point, but I think that is further down the line, we're having
enough trouble figuring things out without that additional complication.
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