Re: pg_autovacuum: short, wide tables

Mark Reid <mail(at)markreid(dot)org> writes:
> I think the issue is that a single update to the main table causes a
> whole bunch of updates to the toast table. So in my case (with the
> vacuum output attached previously), a thousand updates to the main table
> entails tens of thousands of updates to the toast table.

Exactly. If autovac were looking at the properties of the toast table
it would think a vacuum pass was warranted sooner than it thinks from
just looking at the main table.

Admittedly this doesn't come into play unless you have a fairly large
number of toast chunks per main-table row, so the rows in question have
to be really wide (dozens of KB even after compression) before it gets
to be a big deal.

regards, tom lane