From: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
---|---|
To: | eric(dot)mutta(at)gmail(dot)com, pgsql-docs(at)lists(dot)postgresql(dot)org |
Subject: | Re: Should 'sum(mvf)' read 'sum(mcv)'...? |
Date: | 2022-08-22 07:48:37 |
Message-ID: | 20220822074837.dy4i5t7n5xmbhjbw@jrouhaud |
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Lists: | pgsql-docs |
Hi,
On Sun, Aug 21, 2022 at 11:02:04PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/14/row-estimation-examples.html
> Description:
>
> About halfway down this page
> https://www.postgresql.org/docs/current/row-estimation-examples.html we see
> the following formula for calculating selectivity:
>
> > selectivity = (1 - sum(mvf))/(num_distinct - num_mcv)
>
> And just below the formula we see the explanatory sentence saying:
>
> > That is, add up all the frequencies for the MCVs and subtract them from
> one, ...
>
> It appears the above sentence is referring to the "(1 - sum(mvf))" portion
> of the formula, however I am not sure what "mvf" is referring to
> there...shouldn't it be "(1 - sum(mcv))" in order to match what the
> explanatory sentence is saying?
It should be mcf, ie. Most Common Frequencies. It looks like a very old typo
that survived until now.
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