Recursive custom function in Dataflow

[Drshone]

I have a custom function that works fine in Power Query, but when I tried to move it to Dataflow during the refresh it breaks. I have read that in case of recursion in power query/dataflow "@" as inclusive identifier reference be used. But, unfortunately, the custon function is too complex for mayself so I can not find a place where to use inclusive identifier reference. I hope that this could be the reason why the function does't work in Datalow. 

Here is the function, so if anyboddy can hlep.

Spoiler

let
Source = let func =

(ParChTable as table,
ChildKey as text,
ParentKey as text,
LevelColumnName as text) =>
//*/

let
/*/Debug Parameters
ParChTable = SourceData_Loop,
ChildKey = "NodeKey",
ParentKey = "ParentKey",
LevelColumnName = "Name",
*/

SelectRelevantColumns = Table.SelectColumns(ParChTable, {ChildKey, ParentKey, LevelColumnName}),
#"Changed Type" = Table.TransformColumnTypes(SelectRelevantColumns ,{{ChildKey, type text}, {ParentKey, type text}}),
ReplaceNulls = Table.ReplaceValue(#"Changed Type",null,"",Replacer.ReplaceValue,{ParentKey}),
// CleanParChTable = Table.Distinct(ReplaceNulls , {ChildKey, ParentKey}),
MissingParents = List.Buffer(List.Select(List.Difference(List.Distinct(Table.Column(ReplaceNulls , ParentKey)), List.Distinct(Table.Column(ReplaceNulls , ChildKey))), each _ <> "")),
AddMissingParents = Table.Buffer(Table.Combine({ReplaceNulls , #table({ChildKey, LevelColumnName, ParentKey}, List.Transform(MissingParents, each {_, "Unknown TopLevel"& Text.From(List.PositionOf(MissingParents, _)), ""}))})),
#"Merged Queries0" = Table.NestedJoin(AddMissingParents,{ChildKey},AddMissingParents,{ParentKey},"SelectRelevantColumns",JoinKind.LeftOuter),
CheckIfIsLeaf = Table.AddColumn(#"Merged Queries0", "IsLeaf", each if Table.IsEmpty([SelectRelevantColumns]) then "yes" else "no"),
#"Replaced Value1" = Table.ReplaceValue(CheckIfIsLeaf,null,"",Replacer.ReplaceValue,{ParentKey, LevelColumnName}),
AddStartPath = Table.AddColumn(#"Replaced Value1", "Path", each Text.Trim(Record.Field(_, ChildKey)&"|"&Record.Field(_,ParentKey), "|")),
#"Duplicated Column" = Table.DuplicateColumn(AddStartPath, LevelColumnName, "FirstName"),
Feed = Table.DuplicateColumn(#"Duplicated Column", ParentKey, "FirstParentKey"),

// Retrieve all parents per row
fnAllParents = List.Generate(()=>
[Result= Feed, Level=1, EndlessLoop = false, StopEndlessLoop = false],
each Table.RowCount([Result]) > 0 and not [StopEndlessLoop],
each [ Result= let
#"Merged Queries" = Table.NestedJoin([Result],{ParentKey},AddMissingParents,{ChildKey},"Added Custom",JoinKind.Inner),
#"Removed Columns1" = Table.RemoveColumns(#"Merged Queries",{ParentKey}),
#"Expanded Added Custom" = Table.ExpandTableColumn(#"Removed Columns1", "Added Custom", {ParentKey, LevelColumnName}, {"ParentKey.1", "Name.1"}),
#"Duplicated Column" = Table.DuplicateColumn(#"Expanded Added Custom", "ParentKey.1", ParentKey),
#"Merged Columns" = Table.CombineColumns(#"Duplicated Column",{"Path", "ParentKey.1"},Combiner.CombineTextByDelimiter("|", QuoteStyle.None),"Path"),
#"Merged Columns2" = Table.CombineColumns( #"Merged Columns" ,{LevelColumnName, "Name.1"},Combiner.CombineTextByDelimiter("|", QuoteStyle.None),LevelColumnName)
in
Table.Buffer(#"Merged Columns2"),
Level = [Level]+1,
EndlessLoop = List.Sort(List.Distinct(Table.Column(Result, ChildKey))) = List.Sort(List.Distinct(Table.Column([Result], ChildKey))),
StopEndlessLoop = [EndlessLoop]
]),
ConvertToTable = Table.FromList(fnAllParents, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
ExpandLevel = Table.ExpandRecordColumn(ConvertToTable, "Column1", {"Result", "Level", "EndlessLoop"}, {"Result", "Level", "EndlessLoop"}),
ExpandLG = Table.ExpandTableColumn(ExpandLevel, "Result", {LevelColumnName, ParentKey, ChildKey, "Path", "FirstName", "FirstParentKey"}, {"Name", "ParentKey", "NodeKey", "Path", "FirstName", "FirstParentKey"}),
FilterParents = Table.SelectRows(ExpandLG, each ([ParentKey] = null or [ParentKey] = "")),
#"Removed Columns" = Table.RemoveColumns(FilterParents,{"ParentKey"}),
#"Trimmed Text" = Table.TransformColumns(#"Removed Columns",{{"Path", each Text.Trim(_, "|")}}),
ReverseOrderName = Table.TransformColumns(#"Trimmed Text",{{"Name", each Text.Combine(List.Reverse(Text.Split(_, "|")), "|")}}),
ReverseOrderPath = Table.TransformColumns(ReverseOrderName,{{"Path", each Text.Combine(List.Reverse(Text.Split(_, "|")), "|")}}),
#"Reordered Columns" = Table.ReorderColumns(ReverseOrderPath,{"NodeKey", "FirstParentKey", "Path", "FirstName", "Level", "Name"}),
#"Split Column by Delimiter" = Table.SplitColumn(#"Reordered Columns", "Name", Splitter.SplitTextByDelimiter("|", QuoteStyle.Csv), List.Transform({1..Table.RowCount(ConvertToTable)}, each "Level "&Text.From(_))),
#"Merged Queries" = Table.NestedJoin(#"Split Column by Delimiter",{"NodeKey", "FirstParentKey"},ParChTable ,{ChildKey, ParentKey},"Split Column by Delimiter",JoinKind.LeftOuter),
#"Expanded Split Column by Delimiter" = Table.ExpandTableColumn(#"Merged Queries", "Split Column by Delimiter", List.Difference(Table.ColumnNames(ParChTable), Table.ColumnNames(#"Replaced Value1"))),
Rename = Table.RenameColumns(#"Expanded Split Column by Delimiter",{{"Level", "HierarchyDepth"}}),
Parents = List.Buffer(Rename[FirstParentKey]),
IsLeaf = Table.AddColumn(Rename, "IsLeaf", each not List.Contains(Parents, [NodeKey])),
NoOfInterations = List.Count(fnAllParents),
LastIteration = Table.SelectRows(ExpandLG, each ([Level] = NoOfInterations)),
EndlessLoops = LastIteration[EndlessLoop],
IsEndlessLoop = EndlessLoops{0},
RemainingResults = Table.NestedJoin(IsLeaf, {ChildKey}, LastIteration, {ChildKey}, "x", JoinKind.LeftAnti),
Custom1 = if IsEndlessLoop then [Message= "The data is in an endless loop. Check Table in ""Endless Loop""", #" Endless Loop"= LastIteration] meta [ResultsSoFar = RemainingResults] else IsLeaf
in
Custom1
///*
, documentation = [
Documentation.Name = " Table.SolveParentChild
", Documentation.Description = " Creates columns for all parents, multiple parents are supported
" , Documentation.LongDescription = " Creates columns for all parents, multiple parents are supported
", Documentation.Category = " Table
", Documentation.Version = " 2.0: Checking for endless loops
", Documentation.Source = " local
", Documentation.Author = " Imke Feldmann: www.TheBIccountant.com
", Documentation.Examples = {[Description = " See: http://wp.me/p6lgsG-sl for more details
" , Code = "
", Result = "
"]}]
in
Value.ReplaceType(func, Value.ReplaceMetadata(Value.Type(func), documentation))
in
Source

[v-kaiyue-msft · Accepted solution]

Hi @Drshone ,

Here's a simplified way to identify where the ‘@’ symbol might be needed:

In your function, the recursive part seems to be in the fnAllParents definition. You can focus on this part.

In this part, the List.Generate function is used to create a list of tables, where each table represents a level in the hierarchy. Recursion occurs in the each clause of List.Generate.

To use the ‘@’ symbol, you can reference the function itself in the function definition. However, in Power Query M, the ‘@’ symbol is usually used to refer to the current scope of a function, especially nested functions. You should therefore make sure that the function reference is properly scoped and that there are no circular dependencies that would cause recursion to fail.

Best Regards,

Clara Gong

If there is any post helps, then please consider Accept it as the solution  to help the other members find it more quickly.