Re: Why do we let autovacuum give up?

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.kirkwood@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.