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help / color / mirror / Atom feedFrom: Matheus Alcantara <[email protected]>
To: Ilia Evdokimov <[email protected]>
Cc: Guillaume Lelarge <[email protected]>
Cc: Daniel Gustafsson <[email protected]>
Cc: Ibrar Ahmed <[email protected]>
Cc: Gregory Stark (as CFM) <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: Justin Pryzby <[email protected]>
Cc: Peter Geoghegan <[email protected]>
Cc: vignesh C <[email protected]>
Cc: David G. Johnston <[email protected]>
Cc: [email protected]
Subject: Re: explain analyze rows=%.0f
Date: Tue, 11 Feb 2025 11:51:28 -0300
Message-ID: <CAFY6G8cQkCF4FryNpBDec8rjoAyQxVryfidd++5cgUE=JSAZqw@mail.gmail.com> (raw)
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Em seg., 10 de fev. de 2025 às 18:14, Ilia Evdokimov
<[email protected]> escreveu:
> Sorry for missing your question earlier. If you notice in the code above, the variable(average) 'rows' is defined as:
>
> double rows = planstate->instrument->ntuples / nloops;
>
> This represents the total rows divided by the number of loops. The condition
> means that variable 'rows' will always between zero and one. Therefore, the
> average rows under such conditions cannot be greater than or even equal to
> one. I wrote this condition specifically to avoid the verbose expression
> 'rows > 0 && rows < 1'. However, since this might not be obvious to everyone,
> perhaps it'd be better to write is using 'rows' directly or add a comment
> explaining this logic.
>
Thanks for the details! It makes sense to me now. I think that adding a comment
could be a good idea
> I agree with the last two points. As for the first one—maybe we could
> simply state that the average rows value can be decimal, especially for
> very small values?
>
> I'm just not sure about the "small values"; the 'rows' in decimal will only
> happen with small values? What would be a "small value" in this context? My main
> point here is more that I think that it would be good to mention *why* the
> 'rows' can be decimal, not just describe that it could be decimal.
>
>
> As for 'small values', it means that the average rows is between zero and
> one, to avoid rounding errors and misunderstanding. I think this would be
> ideal.
>
Get it, sounds reasonable to me.
--
Matheus Alcantara
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Subject: Re: explain analyze rows=%.0f
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