Hi,

I'm seeing a 8.3 database whose autovacuum-initiated vacuums are being
cancelled and I am not sure of the cause. I am wondering if a HOT
cleanup round on a page could try to acquire locks on it that would
conflict with autovacuum (basically anything that conflicts with a
vacuum lock). This would cause autovacuum to commit hara-kiri.

If the table is frequently updated and HOT is invoked often, this could
be very frequent. The auto-cancel feature of autovacuum is IMHO, in
this case, not welcome. Perhaps we could teach autovac to not cancel
itself if the other locker is a HOT page prune?

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

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  • Tom Lane at Mar 3, 2008 at 10:47 pm

    Alvaro Herrera writes:
    I'm seeing a 8.3 database whose autovacuum-initiated vacuums are being
    cancelled and I am not sure of the cause. I am wondering if a HOT
    cleanup round on a page could try to acquire locks on it that would
    conflict with autovacuum (basically anything that conflicts with a
    vacuum lock). This would cause autovacuum to commit hara-kiri.
    This is nonsense, no? A buffer cleanup lock is an LWLock not a lock
    manager lock.

    regards, tom lane
  • Alvaro Herrera at Mar 4, 2008 at 11:20 am

    Tom Lane wrote:
    Alvaro Herrera <alvherre@commandprompt.com> writes:
    I'm seeing a 8.3 database whose autovacuum-initiated vacuums are being
    cancelled and I am not sure of the cause. I am wondering if a HOT
    cleanup round on a page could try to acquire locks on it that would
    conflict with autovacuum (basically anything that conflicts with a
    vacuum lock). This would cause autovacuum to commit hara-kiri.
    This is nonsense, no? A buffer cleanup lock is an LWLock not a lock
    manager lock.
    Yeah, I realized that after awhile. There must be something else they
    are doing.

    --
    Alvaro Herrera http://www.CommandPrompt.com/
    PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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