On 24/01/14 12:28, Mark Kirkwood wrote:
On 24/01/14 12:13, Jeff Janes wrote:
On Thu, Jan 23, 2014 at 1:41 PM, Mark Kirkwood <
mark.kirkw...@catalyst.net.nz> wrote:
On 24/01/14 10:16, Mark Kirkwood wrote:
On 24/01/14 10:09, Robert Haas wrote:
On Thu, Jan 23, 2014 at 4:03 PM, Mark Kirkwood
<mark.kirkw...@catalyst.net.nz> wrote:
On 24/01/14 09:49, Tom Lane wrote:
2. What have you got that is requesting exclusive lock on
pg_attribute?
That seems like a pretty unfriendly behavior in itself. regards,
tom
lane
I've seen this sort of problem where every db session was busily
creating
temporary tables. I never got to the find *why* they needed to
make so
many,
but it seemed like a bad idea.
But... how does that result on a vacuum-incompatible lock request
against pg_attribute?
I see that it'll insert lots of rows into pg_attribute, and maybe
later delete them, but none of that blocks vacuum.
That was my thought too - if I see it happening again here (was a
year or
so ago that I saw some serious pg_attribute bloat) I'll dig deeper.
Actually not much digging required. Running the attached script via
pgbench (8 sessions) against a default configured postgres 8.4 sees
pg_attribute get to 1G after about 15 minutes.
At that rate, with default throttling, it will be a close race whether
autovac can vacuum pages as fast as they are being added. Even if it
never
gets cancelled, it might not ever finish.
Yes - I should have set the cost delay to 0 first (checking that now).
Doing that (and a few other autovac tweaks):
autovacuum_max_workers = 4
autovacuum_naptime = 10s
autovacuum_vacuum_scale_factor = 0.1
autovacuum_analyze_scale_factor = 0.1
autovacuum_vacuum_cost_delay = 0ms
Stops excessive bloat - clearly autovacuum *is* able to vacuum
pg_attribute in this case. Back to drawing board for a test case.
Regards
Mark
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