NEW Column length limit in dataflows messing existing linked tables up!

[Anonymous]

We are working with dataflows and linked entities.

After the recent update, it apparently checks for too long column names. This used to be fine, so I have an existing linked table with column names deemed too long now. So a dataflow that uses this linked table goes crazy: saving a dataflow first adds a Rename operation to the linked table and then complains that Linked tables can't be modified.

Please help! This all used to work before the update!

[Anonymous]

Thanks, but that's not the point. It has to be a linked table,I want to use the functionality.

But now PowerBI introduces automatic column renamings also on linked tables, which is impossible!

[Daryl-Lynch-Bzy]

Hi @Anonymous - I am sorry I misunderstood the problem.  There appears to be an undocumented rule in Dataflows that limits the length of column name to 80 characters.  I am sorry but you will need to revise the column name lengths below 80 to avoid the Dataflow validation rule and forced truncation.  I have attached examples below.  

I suggest that you shorten the Column Names, but include the longer name in the Column Descripition in the Power BI datasets.  Unfortunately, I am not aware that this piece of metadata can be passed from the Dataflow to Dataset.

//"Example" Dataflow

let
  Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCs7PTVVwSSxJVIqNBQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"1234567890" = _t])
in
  Source

//"Linked Entity" - this references Example dataflow then changes the name.  The step #"Renamed columns 1"

let
  Source = #"Example",
  //This step was added manually by the developer
  #"Renamed columns" = Table.RenameColumns(Source, {{"1234567890", "123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"}}),
  #"Added custom" = Table.AddColumn(#"Renamed columns", "Attempted Column Length", each Text.Length( Table.ColumnNames(#"Renamed columns"){0}), Int64.Type),
  // This step was added by the Dataflow validation process
  #"Renamed columns 1" = Table.RenameColumns(#"Added custom", {{"123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890", "12345678901234567890123456789012345678901234567890123456789012345678901234567890"}}),
  Custom = Table.AddColumn(#"Renamed columns 1", "Revised Column Length", each Text.Length( Table.ColumnNames(#"Renamed columns 1"){0} ) , Int64.Type)
in
  Custom

[Daryl-Lynch-Bzy]

@Anonymous - when you link to the dataflow table "PricingReport" and enable load, Power Query will prevent you from making any modifications within the query.   Essentially, the table will need to re-published like-for-like.  Instead, if you disable the load in the original query and then reference it in a second query, you will be able to make changes and load the modifications.