Count number of records in a column for all columns

[MladenJ]

Hi,

I'm trying to evaluate all columns in one big table (99 columns, 1.5m rows).

What i need get is the list of all columns and the count of how many records are there in the respective column.

Table has various column types: dates, strings, numbers, boolean values.

What is the best approach to do this?

What i've tried so far are List functions, but it either seems too long for the refresh (over an hour and a half).

My first step was to get the column names from the fact table and second step is to count the records in selected column as list.

let
    Table = data,
    Source = Table.FromList(Table.ColumnNames(Table), Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    RecordCount = Table.AddColumn(Source, "Record count", each try List.NonNullCount( List.ReplaceMatchingItems( Table.ToList(Table.SelectColumns(Table, [Column1])), {{"", null}} )) otherwise 
List.Count( Table.ToList(Table.SelectColumns(Table, [Column1])) ))
in
    RecordCount

I found that the List.Count or List.NonNullCount don't work as expected, as i have nulls in the list, but it counts them either way.

[wdx223_Daniel · Accepted solution]

NewStep=Table.FromColumns({Table.ColumNames(PreviousStepName),List.Transform(Table.ToColumns(PrevousStepName),each List.Count(List.RemoveItems(_,{"",null})))},{"ColName","NoNullCount"})

[MladenJ]

Thanks, that works, but it still takes really long time to refresh. (hour for now)

I'm not too knowledgeable in PQ, but i've read the posts and use cases for Buffer functions. 

Are they any good in this case?