Re: [HACKERS] Autovacuum loose ends

On Fri, Aug 12, 2005 at 03:49:57PM -0700, Mark Wong wrote:
> On Fri, 12 Aug 2005 18:42:09 -0400
> Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

> > Also, it seems the "tran_lock.out" file captured wrong input -- I think
> > you mean "WHERE transactionid IS NULL" in the query instead of "WHERE
> > transaction IS NULL".
>
> Hmm, ok I can try that in a future test run.  I'm not very familiar with
> this table, what's the difference between transaction and transactionid?

transaction is the Xid of the transaction holding or waiting for the
lock.  transactionid is not null in the case where the lock is for a
TransactionId.  I guess it depends on what do you want though -- now
that I think about it, capturing only transaction locks is very likely
not what you want.

http://developer.postgresql.org/docs/postgres/view-pg-locks.html

I wonder why do you have that condition though.  I don't think
"transaction" can ever be NULL in that view.

--
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"Hay dos momentos en la vida de un hombre en los que no debería
especular: cuando puede permitírselo y cuando no puede" (Mark Twain)