From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Peter Eisentraut <peter_e(at)gmx(dot)net>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org, Nathan Boley <npboley(at)gmail(dot)com> |
Subject: | Re: Thoughts on statistics for continuously advancing columns |
Date: | 2010-01-01 18:44:18 |
Message-ID: | 1262371458.19367.16367.camel@ebony |
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Lists: | pgsql-hackers |
On Thu, 2009-12-31 at 21:29 +0000, Simon Riggs wrote:
> On Thu, 2009-12-31 at 15:18 -0500, Tom Lane wrote:
> > Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> > > Why not get both max() and min(), then rebase the histogram according to
> > > those values. That way the histogram can still move significantly and
> > > the technique will still work.
> >
> > Define "rebase", keeping in mind that this has to work on datatypes that
> > we don't have a distance metric for.
>
> Make it work differently according to whether we have, or not, just as
> we do elsewhere with stats. No point in limiting ourselves to the lowest
> common denominator, especially when the common case is integer keys and
> time datatypes.
This seemed obvious but I understand now that you meant we don't know
that from the datatype definition, so we can't do as I suggested, yet.
--
Simon Riggs www.2ndQuadrant.com
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