Re: Measuring relation free space

On 11/28/2011 05:40 AM, Greg Smith wrote:
> Ignoring fillfactor seems to have even more downsides as I see it.  
> Certainly deserves a doc improvement, as well as fixing the 
> description of the value so it's clearly a ratio rather than a true 
> percentage.

So:  I'm very clear on what to do here now:

-Make the computation be in units that match it documetnation
-Take a look at other index types, as well as TOAST, at least to get the 
easy ones right.
-Fully confirm the extension upgrade logic works as hoped

That's the must do stuff.  Then there's two more features to consider 
and do something with if sensible:

-Double check whether there is really a useful role in using 
pg_freespace here.  I don't think the numbers will be as good, but maybe 
we don't care.
-Once the above is all sorted, add a second UI that samples some pages 
and extrapolates, ANALYZE-style, rather than hitting everything.

This ones leaves as returned with feedback, feeling pretty good it will 
be whipped into good shape for the last 9.2 CommitFest.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us