Table.buffer slow

Hi Anonymous ,

If the following code is used without the Table.Buffer function, how long does it take? If it takes longer, then I think using DAX instead of M code would be a better choice.

let
    Source = Excel.Workbook(File.Contents("\.....\CASE SAMPLE DATA\RAAK - storingen per maand.xlsx"), null, true),
    Sheet1_Sheet = Source{[Item="Sheet1",Kind="Sheet"]}[Data],
    #"Promoted Headers" = Table.PromoteHeaders(Sheet1_Sheet, [PromoteAllScalars=true]),
    #"Changed Type" = Table.TransformColumnTypes(#"Promoted Headers",{{"Serial Number", Int64.Type}, {"Jaar maand", type date}, {"Equipment Series", type text}, {"Work Center", type text}, {"SR Number", Int64.Type}, {"SR Stranded Train Number", Int64.Type}, {"SR Safety Number", Int64.Type}, {"EBK Number", Int64.Type}, {"Recidivist", Int64.Type}, {"Q_label_score_maand", Int64.Type}, {"Qlabelscore_laatste_3_maanden", Int64.Type}, {"Qlabel", type text}}),
    #"Removed Columns" = Table.RemoveColumns(#"Changed Type",{"Qlabelscore_laatste_3_maanden"}),
    #"Inserted Date" = Table.AddColumn(#"Removed Columns", "Datum", each Date.From([Jaar maand]), type date),
    #"Adds 3 months back" = Table.AddColumn(#"Inserted Date", "Date", each Date.AddMonths([Datum],-3), type date),
    #"Adds last 3 months" = Table.AddColumn(#"Adds 3 months back", "Q-Score 3mnd", each let 
    myfunction = (CurrentSerial, CurrentEquipment, CurrentWorkCenter,sdate, edate) => 
     let 
       SelectRows = Table.SelectRows(#"Adds 3 months back", each [Serial Number] = CurrentSerial and [Equipment Series] = CurrentEquipment and [Work Center] = CurrentWorkCenter and [Datum] >= sdate and [Datum] < edate) 
     in 
       SelectRows,
   Data = List.Sum(myfunction([Serial Number],[Equipment Series],[Work Center],[Date],[Datum])[Q_label_score_maand])
in 
   Data),
    #"Qlabel 3mnd" = Table.AddColumn(#"Adds last 3 months", "Q_lable_3mnd", each if [#"Q-Score 3mnd"] <= 9 then "A" else if [#"Q-Score 3mnd"] <= 12 then "B" else if [#"Q-Score 3mnd"] <= 14 then "C" else if [#"Q-Score 3mnd"] <= 17 then "D" else if [#"Q-Score 3mnd"] <= 22 then "E" else if [#"Q-Score 3mnd"] <= 30 then "F" else if [#"Q-Score 3mnd"] >= 31 then "G" else null),
    #"Qlabel 3mnd Fouten vervangen" = Table.ReplaceErrorValues(#"Qlabel 3mnd", {{"Q_lable_3mnd", null}}),
    #"Aangepaste kolom toegevoegd" = Table.AddColumn(#"Qlabel 3mnd Fouten vervangen", "Vandaaag", each DateTime.LocalNow())
in
    #"Aangepaste kolom toegevoegd"

If the problem is still not resolved, please provide detailed error information or the expected result you expect. Let me know immediately, looking forward to your reply.
Best Regards,
Winniz
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