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From: Andrey Lepikhov <[email protected]>
To: Amit Kapila <[email protected]>
To: Justin Pryzby <[email protected]>
Cc: Peter Geoghegan <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Greg Stark <[email protected]>
Cc: vignesh C <[email protected]>
Cc: Ibrar Ahmed <[email protected]>
Cc: David G. Johnston <[email protected]>
Cc: pgsql-hackers <[email protected]>
Cc: Simon Riggs <[email protected]>
Cc: Ron Mayer <[email protected]>
Cc: Euler Taveira de Oliveira <[email protected]>
Cc: Tom Lane <[email protected]>
Subject: Re: explain analyze rows=%.0f
Date: Mon, 7 Nov 2022 10:20:59 +0600
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAA4eK1Lmo0FX6Nfr_k3-UX1Hpei1H-xPHL6Wwx7SLUP3s+O1mA@mail.gmail.com>
References: <CA+TgmoZv8DvmeQHQAX+rkn68id2N+DoUhFZB36d-_w1tyAeqeA@mail.gmail.com>
	<[email protected]>
	<CAA4eK1Lmo0FX6Nfr_k3-UX1Hpei1H-xPHL6Wwx7SLUP3s+O1mA@mail.gmail.com>

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

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