Message-ID: <a9393107-6bb9-c835-50b7-c0f453a514b8@postgrespro.ru>
Date: Mon, 7 Nov 2022 10:20:59 +0600
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Subject: Re: explain analyze rows=%.0f
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To: Amit Kapila <amit.kapila16@gmail.com>,
 Justin Pryzby <pryzby@telsasoft.com>
Cc: Peter Geoghegan <pg@bowt.ie>, Robert Haas <robertmhaas@gmail.com>,
 Greg Stark <stark@mit.edu>, vignesh C <vignesh21@gmail.com>,
 Ibrar Ahmed <ibrar.ahmad@gmail.com>,
 "David G. Johnston" <david.g.johnston@gmail.com>,
 pgsql-hackers <pgsql-hackers@postgresql.org>,
 Simon Riggs <simon@2ndquadrant.com>,
 Ron Mayer <rm_pg@cheapcomplexdevices.com>,
 Euler Taveira de Oliveira <euler@timbira.com>, Tom Lane <tgl@sss.pgh.pa.us>
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 <20220707222015.GD13040@telsasoft.com>
 <CAA4eK1Lmo0FX6Nfr_k3-UX1Hpei1H-xPHL6Wwx7SLUP3s+O1mA@mail.gmail.com>
From: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
Organization: Postgres Professional
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On 22/7/2022 16:47, Amit Kapila wrote:
> I feel the discussion has slightly deviated which makes it unclear
> whether this patch is required or not?

After quick review I want to express my thoughts.
At first, We have been waiting for this feature for years. Often clients 
give an explain to us where we see something like:
"rows=0, loops=1000000".
Without verbose mode, I can't even understand whether this node produces 
any rows or not.
So, I think this feature is useful for parameterized plans mostly.
Also, printing two decimal digits or even three isn't meaningful - 
sometimes we have a plan where number of loops is about 1E6 or even 1E7, 
but number of real rows is equal 100 or 1000.
To overcome this issue, I see two options:
1. Show the exact number of tuples without division by loops (fair case 
but invasive and bad for automation tools).
2. Show rows in scientific format like X.XXEXX.
I vote for second option.

-- 
regards,
Andrey Lepikhov
Postgres Professional