Re: incorrect information in documentation
| От | David G. Johnston |
|---|---|
| Тема | Re: incorrect information in documentation |
| Дата | |
| Msg-id | CAKFQuwbHsQ14v3i4oEwPOmgEBqEFjG4i=WsuOMmP2q82myvdQQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | incorrect information in documentation (PG Doc comments form <noreply@postgresql.org>) |
| Ответы |
Re: incorrect information in documentation
|
| Список | pgsql-docs |
On Mon, Aug 9, 2021 at 8:02 AM PG Doc comments form <noreply@postgresql.org> wrote:
Hello, on page
https://www.postgresql.org/docs/current/row-estimation-examples.html - there
is a example:
selectivity = (1 - null_frac1) * (1 - null_frac2) * min(1/num_distinct1,
1/num_distinct2)
= (1 - 0) * (1 - 0) / max(10000, 10000)
= 0.0001
in the first string " * min" and in the second " / max"
as I understand it isn't correct.
Division is just multiplication by the reciprocal so while the presentation here is inconsistent it is correct. Likewise, the larger a number the smaller its reciprocal, so the change from min to max also works.
David J.
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