Re: a fast bloat measurement tool (was Re: Measuring relation free space)

From: Abhijit Menon-Sen <ams(at)2ndQuadrant(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>
Subject: Re: a fast bloat measurement tool (was Re: Measuring relation free space)
Date: 2015-05-11 19:12:14
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At 2015-05-11 19:15:47 +0200, andres(at)anarazel(dot)de wrote:
> TBH, I'd rather not touch unrelated things right now. We're pretty
> badly behind...

OK. That patch is independent; just ignore it.

> I don't really care how it's named, as long as it makes clear that
> it's not an exact measurement.

Not having heard any better suggestions, I picked "pgstatapprox" as a
compromise between length and familiarity/consistency with pgstattuple.

> > Should I count the space it would have free if it were initialised,
> > but leave the page alone for VACUUM to deal with?

And this is what the attached patch does.

I also cleaned up a few things that I didn't like but had left alone to
make the code look similar to pgstattuple. In particular, build_tuple()
now does nothing but build a tuple from values calculated earlier in

Thank you.

-- Abhijit

P.S. What, if anything, should be done about the complicated and likely
not very useful skip-only-min#-blocks logic in lazy_scan_heap?

Attachment Content-Type Size
0001-Add-pgstatapprox-to-pgstattuple.patch text/x-diff 17.5 KB

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