Re: set autovacuum=off

On 2/23/2012 6:34 AM, Thom Brown wrote:

On 22 February 2012 23:50, Alessandro Gagliardi<alessandro@path.com>  wrote:

I have a database where I virtually never delete and almost never do
updates. (The updates might change in the future but for now it's okay to
assume they never happen.) As such, it seems like it might be worth it to
set autovacuum=off or at least make it so vacuuming hardly ever occurs.
Actually, the latter is probably the more robust solution, though I don't
know how to do that (hence me writing this list). I did try turning
autovacuum off but got:

ERROR: parameter "autovacuum" cannot be changed now
SQL state: 55P02

Not sure what, if anything, I can do about that.

Autovacuum is controlled by how much of a table has changed, so if a
table never changes, it never gets vacuumed (with the exceptional case
being a forced vacuum freeze to mitigate the transaction id
wrap-around issue).  The settings which control this are
autovacuum_vacuum_threshold and autovacuum_vacuum_scale_factor.
Therefore it isn't necessary to disable autovacuum.

But if you are adamant about disabling it, you need to change it in
your postgresql.conf file and restart the server.

Agreed, don't disable autovacuum.  It's not that demanding, and if you do need it and forget to run it, it might cause you more problems.

I have a db that's on a VM that doesnt get hit very much.  I've noticed IO is a little busy (we are talking small percents of percents less than one) but still more that I thought should be happening on a db with next to no usage.

I found setting autovacuum_naptime = 6min made the IO all but vanish.

And if I ever get a wild hair and blow some stuff away, the db will clean up after me.

-Andy