On Tue, Feb 11, 2025 at 12:14 PM Andrei Lepikhov <lepi...@gmail.com> wrote: > 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.
I agree strongly with all of this. I believe we should just implement what was agreed here: https://www.postgresql.org/message-id/21013.1243618236%40sss.pgh.pa.us Let's just display 2 fractional digits when nloops>1, else 0, and call it good. -- Robert Haas EDB: http://www.enterprisedb.com
