Re: Database-wide vacuum can take a long time, during which

Steven Flatt wrote:
> Here is a potential problem with the auto-vacuum daemon, and I'm
> wondering if anyone has considered this.  To avoid transaction ID
> wraparound, the auto-vacuum daemon will periodically determine that it
> needs to do a DB-wide vacuum, which takes a long time.  On our system,
> it is on the order of a couple of weeks.  (The system is very busy and
> there is a lot of I/O going on pretty much 24/7).  During this period of
> time, there is nothing to automatically analyze any of the tables,
> leading to further performance problems.  What are your thoughts on
> having the DB-wide vacuum running on a separate thread so that the
> daemon can concurrently wake up and take care of analyzing tables?

Two issues here:
1)XID Wraparound:  There has been work done on this already, and in 8.2
I believe there will no longer be a requirement that a database wide
vacuum be issued, rather, XID wraparound will be managed on a per table
basis rather than per database, so that will solve this problem.

2)Concurrent Vacuuming:  There has been a lot of talk about
multiple-concurrent vacuums and I believe that this is required in the
long run, but it's not here yet, and won't be in 8.2, hopefully it will
get done for 8.3.


Matt