Processing of lists is very slow

[Anonymous]

I experience a severe performance issue with the evalution of lists:

The column Values of Table contains about 4000 lists with in average about 2 items.

The evaluation of

Output = List.Combine(Table[Values])

runs at only about 3 list/second!

The similar command 

Output = Table.AddColumn(Table, "Count", each List.Count([Values]), Int64.Type),
MaxNrOfValues = List.Max(Output[Count])

is comparably slow.

Does list processing in Power Query generally need a lot of resources? How can I optimize this?

[watkinnc]

Wrap your Table[Column] in List.Buffer, like

List.Buffer(Table[Column])

You can do it right there in your formulas for all of your lists. You will likely see very significant improvements.

--Nate

[Anonymous]

I thought so too but it unfortunately has no significant impact on the performance.

It's impossible to confirm small improvements as benchmarking of Power Queries under Excel is generally very unreproducible.