| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Nathan Boley <npboley(at)gmail(dot)com> |
| Subject: | Re: Thoughts on statistics for continuously advancing columns |
| Date: | 2009-12-30 03:08:33 |
| Message-ID: | 7216.1262142513@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Josh Berkus <josh(at)agliodbs(dot)com> writes:
> My thoughts on dealing with this intelligently without a major change to
> statstics gathering went along these lines:
> 1. add columns to pg_statistic to hold estimates of upper and lower
> bounds growth between analyzes.
This seems like a fundamentally broken approach, first because "time
between analyzes" is not even approximately a constant, and second
because it assumes that we have a distance metric for all datatypes.
(Note that convert_to_scalar does not assume that it can measure
arbitrary distances, but only fractions *within* a histogram bucket;
and even that is pretty shaky.)
I don't have a better idea at the moment :-(
regards, tom lane
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