Re: explain analyze rows=%.0f

From: Andrei Lepikhov <lepihov(at)gmail(dot)com>
To: Ilia Evdokimov <ilya(dot)evdokimov(at)tantorlabs(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Matheus Alcantara <matheusssilv97(at)gmail(dot)com>, Guillaume Lelarge <guillaume(at)lelarge(dot)info>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, "Gregory Stark (as CFM)" <stark(dot)cfm(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, vignesh C <vignesh21(at)gmail(dot)com>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Alena Rybakina <a(dot)rybakina(at)postgrespro(dot)ru>
Subject: Re: explain analyze rows=%.0f
Date: 2025-02-19 15:37:40
Message-ID: c9f91659-f17d-41f4-ad16-2801cf61b608@gmail.com
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On 19/2/2025 15:01, Ilia Evdokimov wrote:
> If we want to convey this information more clearly, we should consider a
> more explicit approach. For example, instead of using a fractional
> value, we could display the minimum and maximum row counts observed
> during execution (e.g.,rows=10..20, formatting details could be
> discussed). However, in my opinion, this discussion is beyond the scope
> of this thread.
I think this approach is redundant. Usually, a problem is an unknown
number of tuples because, having millions of loops, we produce a small
number of tuples, but each tuple costs a lot because of a subplan or
something like that. By printing fractional digits (of course, we need
to view significant ones, but we already agreed on a couple of digits
for now), we may resolve this corner-case problem fully - at least all
examples in my experience would be resolved, and I have even maintained
a patch for years to manage this.
Moreover, it is too simple to implement. I just can't imagine why not to
do it right now.

--
regards, Andrei Lepikhov

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