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Date: Tue, 11 Feb 2025 18:14:49 +0100
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Subject: Re: explain analyze rows=%.0f
To: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>,
 Matheus Alcantara <matheusssilv97@gmail.com>
Cc: Guillaume Lelarge <guillaume@lelarge.info>,
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 "David G. Johnston" <david.g.johnston@gmail.com>,
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From: Andrei Lepikhov <lepihov@gmail.com>
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On 8/2/2025 04:28, Ilia Evdokimov wrote:
> On 08.02.2025 00:01, Matheus Alcantara wrote:
>> Just for reference I'm trying to apply based on commit fb056564ec5.
> You are right, because two commits were appeared after creating v6-patch 
> on partition_prune.out and patch v6 must not have applied on master. 
> Then I created v7 patch rebased on fb056564ec5 . Thank for your remark!
I support the idea in general, but I believe it should be expanded to 
cover all cases of parameterised plan nodes. Each rescan iteration may 
produce a different number of tuples, and rounding can obscure important 
data.

For example, consider five loops of a scan node: the first loop returns 
nine tuples, and each other - zero tuples. When we calculate the 
average, 9 divided by 5 equals 1.8. This results in an explanation that 
indicates "rows = 1," masking almost 40% of the data.

Now, if we apply the same two loops but have a total of 900,000 tuples, 
then 400,000 masked tuples represent a significant portion of the data.

Moreover, switching to a floating-point type for row explanations in 
each parameterised node would provide a more comprehensive view and add 
valuable information about the parameterisation of the node, which may 
not be immediately apparent.

-- 
regards, Andrei Lepikhov