| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Stark <gsstark(at)mit(dot)edu>, Marko Ristola <marko(dot)ristola(at)kolumbus(dot)fi>, pgsql-perform <pgsql-performance(at)postgresql(dot)org>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] Bad n_distinct estimation; hacks suggested? |
| Date: | 2005-04-26 20:45:53 |
| Message-ID: | 200504261345.54164.josh@agliodbs.com |
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| Thread: | |
| Lists: | pgsql-hackers pgsql-performance |
Simon,
> Could it be that we have overlooked this simple explanation and that the
> Haas and Stokes equation is actually quite good, but just not being
> applied?
That's probably part of it, but I've tried Haas and Stokes on a pure random
sample and it's still bad, or more specifically overly conservative.
--
--Josh
Josh Berkus
Aglio Database Solutions
San Francisco
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