Re: Per table autovacuum vacuum cost limit behaviour strange

Alvaro Herrera wrote:

> So my proposal is a bit more complicated.  First we introduce the notion
> of a single number, to enable sorting and computations: the "delay
> equivalent", which is the cost_limit divided by cost_delay.

Here's a patch that implements this idea.  As you see this is quite a
bit more complicated that Haribabu's proposal.

There are two holes in this:

1. if you ALTER DATABASE to change vacuum delay for a database, those
values are not considered in the global equiv delay.  I don't think this
is very important and anyway we haven't considered this very much, so
it's okay if we don't handle it.

2. If you have a "fast worker" that's only slightly faster than regular
workers, it will become slower in some cases.  This is explained in a
FIXME comment in the patch.

I don't really have any more time to invest in this, but I would like to
see it in 9.4.  Mark, would you test this?  Haribabu, how open are you
to fixing point (2) above?

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services