| From: | John Naylor <jcnaylor(at)gmail(dot)com> |
|---|---|
| To: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: MCV lists for highly skewed distributions |
| Date: | 2018-02-04 12:18:26 |
| Message-ID: | CAJVSVGUebFUD3VxyKKSbFP7SLhSwvkSymGinVSQUcZ7X8QzkDg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 2/2/18, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> wrote:
> I think it would be better to try to come up with an alternative
> algorithm that has a better theoretical basis, and then test that to
> see how it holds up in practice.
>
> With that in mind, attached is a patch based on the idea of setting a
> bound on the relative standard error on the sample frequency
I did the same basic eyeball testing I did on earlier patches, and
this is the best implementation so far. I've attached some typical
pg_stats contents for HEAD and this patch. More rigorous testing,
including of planner estimates on real data, is still needed of
course, but I think this is definitely in the right direction.
-John Naylor
| Attachment | Content-Type | Size |
|---|---|---|
| test_mcvstats_v1.sql | application/sql | 4.1 KB |
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