Re: autovacuum next steps, take 2

Jim C. Nasby wrote:
> On Thu, Feb 22, 2007 at 10:32:44PM -0500, Matthew T. O'Connor wrote:

> > I'm not sure this is a great idea, but I don't see how this would result
> > in large numbers of workers working in one database. If workers work
> > on tables in size order, and exit as soon as they catch up to an older
> > worker, I don't see the problem. Newer works are going to catch-up to
> > older workers pretty quickly since small tables will vacuum fairly quickly.
>
> The reason that won't necessarily happen is because you can get large
> tables popping up as needing vacuuming at any time.

Right.

We know that a table that needs frequent vacuum necessarily has to be
small -- so maybe have the second worker exit when it catches up with
the first, or when the next table is above 1 GB, whichever happens
first. That way, only the first worker can be processing the huge
tables. The problem with this is that if one of your hot tables grows
a bit larger than 1 GB, you suddenly have a change in autovacuuming
behavior, for no really good reason.

And while your second worker is processing the tables in the hundreds-MB
range, your high-update 2 MB tables are neglected :-(

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