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Tom_Y's avatar
Tom_Y
Advocate II
2 years ago
Solved

List.Buffer (Will it refresh automatically?)

Hi,

I'm having these 3 lines in power query to get the column headers of multiple tables before I go back and expand them, so all columns in all tables are extracted. It's too slow until I add "List.Buffer" to the list HEADINGS, and it's now running smoothly.

 

Somewhere said the buffered list is stored in memory. Will it be updated when I click refresh, or scheduled refreshing (BI Services) in mid-night? I'm afraid new columns are added in one of those tables, and the code do not update and extract the data. Thanks in advance.

 

PreExpand = Table.SelectColumns(#"Invoke Custom Function1",{"Transform File"}),

HEADINGS = List.Buffer(List.Union(List.Transform(PreExpand[Transform File], each Table.ColumnNames(_)))),
ReadyToExpand = PreExpand,
#"Expanded Transform File" = Table.ExpandTableColumn(ReadyToExpand, "Transform File", HEADINGS)

Need Help
  • lbendlin's avatar
    lbendlin
    2 years ago

    List.Buffer has no logic or meta data impact on your transforms, it "only"  improves their performance.

     

    You may also want to List.Buffer the column names.

1 Reply

  • lbendlin's avatar
    lbendlin
    Super User
    2 years ago

    List.Buffer has no logic or meta data impact on your transforms, it "only"  improves their performance.

     

    You may also want to List.Buffer the column names.