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.