| From: | Michael Christofides <michael(at)pgmustard(dot)com> |
|---|---|
| To: | Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru> |
| Cc: | Julien Rouhaud <rjuju123(at)gmail(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, e(dot)sokolova(at)postgrespro(dot)ru, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Subject: | Re: [PATCH] Add extra statistics to explain for Nested Loop |
| Date: | 2021-01-18 11:45:09 |
| Message-ID: | CAFwT4nDbor4JMkH1_wocbmvt-U39V0mgrWY9dXDk_mP6Hi-uyg@mail.gmail.com |
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| Lists: | pgsql-hackers |
> New version of this patch prints extra statistics for all cases of
> multiple loops, not only for Nested Loop. Also I fixed the example by
> adding VERBOSE.
>
> Please don't hesitate to share any thoughts on this topic!
Thanks a lot for working on this! I really like the extra details, and
including it only with VERBOSE sounds good.
> rows * loops is still an important calculation.
>
> Why not just add total_rows while we are at it - last in the listing?
>
> (actual rows=N loops=N min_rows=N max_rows=N total_rows=N)
This total_rows idea from David would really help us too, especially
in the cases where the actual rows is rounded down to zero. We make an
explain visualisation tool, and it'd be nice to show people a better
total than loops * actual rows. It would also help the accuracy of
some of our tips, that use this number.
Apologies if this input is too late to be helpful.
Cheers,
Michael
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