Hi Tom,
till now i found more blocking vacuum processes in other databases as well.
we migrated postgres from 8.3 to 8.4 in april.
on most databases we have slony running - they have a good potential for getting to that high number of transactions. only that they do their own vacuum on the most frequented tables.
what exactly happens during anti-wraparond vacuum in terms of locking and for how long?
best regards,
Uwe
On 22 June 2010 16:48, Tom Lane
<tgl@sss.pgh.pa.us> wrote:
Uwe Bartels <
uwe.bartels@gmail.com> writes:
> last ween i've seen a blocking "automatic vacuum".
> as i understood, this is not supposed to happen. in the past i saw vacuum
> processes disappear, in case of the need of a lock.
won't cancel those to avoid delaying other processes.
Now, RowExclusiveLock doesn't conflict with an autovacuum, so there is
more going on here than you've showed us. The other obvious question is
how did you get to the point where an anti-wraparound vacuum became
necessary.
I speculate that you are doing something that does conflict with vacuum
(ie, SHARE UPDATE EXCLUSIVE lock or higher), and are doing it so often
that regular autovacuum runs on the table never manage to complete.
This is very bad, because you're going to have a serious bloat problem
if autovac keeps getting canceled. You need to look at what sort of DDL
you are repetitively executing on that table, and find a way to do it a
lot less often.
regards, tom lane
