Re: explain analyze rows=%.0f

On Fri, Jul 8, 2022 at 3:50 AM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
>
> On Thu, Jul 07, 2022 at 04:21:37PM -0400, Robert Haas wrote:
> > I mean, what I really want here if I'm honest is to not have the
> > system divide the number of rows by the loop count. And it sort of
> > sounds like maybe that's what you want, too. You want to know whether
> > the loop count is actually zero, not whether it's close to zero when
> > you divide it by some number that might be gigantic.
> ...
> > involves a dozen or two different nested loops, and if we didn't
> > insist on dividing the time by the loop count, it would be MUCH EASIER
> > to figure out whether the time spent in the Index Scan is a
> > significant percentage of the total time or not.
>
> I think the guiding princible for what to do should be to reduce how much is
> needed to explain about how to interpret what explain is showing...
>
> The docs say this:
> | In such cases, the loops value reports the total number of executions of the
> | node, and the actual time and rows values shown are averages per-execution.
> | This is done to make the numbers comparable with the way that the cost
> | estimates are shown. Multiply by the loops value to get the total time
> | actually spent in the node.
>
> On Thu, Jul 07, 2022 at 01:45:19PM -0700, Peter Geoghegan wrote:
> > Plus you could probably
> > make some kind of concession in the direction of maintaining
> > compatibility with the current approach if you had to. Right?
>
> The minimum would be to show the information in a way that makes it clear that
> it's "new style" output showing a total and not an average, so that a person
> who sees it knows how to interpret it (same for the web "explain tools")
>
> A concession would be to show the current information *plus* total/raw values.
>
> This thread is about how to display the existing values.
>

I feel the discussion has slightly deviated which makes it unclear
whether this patch is required or not?

--
With Regards,
Amit Kapila.