Re: [HACKERS] Reporting xmin from VACUUMs

On 2/19/17 3:43 AM, Robert Haas wrote:
> This is the kind of information that you really want to see once per
> autovac, though, not just the most recent autovac or some kind of
> cumulative total.  Knowing that I've done 301 index scans in my last
> 300 vacuums is not nearly as useful as knowing which autovacuum did 2
> index scans and what exactly was going on with that vacuum.  So I'm
> not sure including this sort of thing in the stats files would be very
> useful, or at least you'd want to think carefully about how to do it.

Well, counters would be better than nothing I think, but I agree with 
your concern. Really, that's a problem for the entire stats system to 
varying degrees.

> As far as bloating the stats file is concerned, the big problem there
> is that our current design for the stats file requires rewriting the
> entire thing any time we want to update even a single byte of data.
> We could fix that by splitting up the files more so that they are
> smaller and faster to rewrite, but we could also fix it by coming up
> with a way of rewriting just one part of a file instead of the whole
> thing, or we could think about storing it in DSM so that you don't
> have to rewrite anything at all.  I think that last option is worth
> some serious study now that we have DSA, but it's currently not very
> high on my personal priority list.

Hmm... so basically replace the temporary file with DSM?

Something else I think would be useful is a way to subscribe to stats 
updates.
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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