Dataflow Gen2: issue while refreshing - Error Code: Mashup Exception Expression Erro

[XCT]

Hi,

I'm facing an issue to refresh a dataflow Gen2. It works well in the PowerQuery Interface.

But when I try to run the refresh, I encounter that error message on a table...

Here is the message (sorry t's in french):

Error Code: Mashup Exception Expression Error, Error Details: Couldn't refresh the entity because of an issue with the mashup document MashupException.Error: Expression.Error: Échec de l’insertion d’un tableau., InnerException : Désolé... Nous n'avons pas pu appliquer l'opérateur - aux types Table et Table., Erreur sous-jacente : Désolé... Nous n'avons pas pu appliquer l'opérateur - aux types Table et Table. Details: Reason = Expression.Error;ErrorCode = Lakehouse036;Message = Désolé... Nous n'avons pas pu appliquer l'opérateur - aux types Table et Table.;Detail = [Operator = "-", Left = error "Microsoft.Mashup.Engine1.Runtime.ValueException: [Expression.Error] La valeur n'a pas été spécifiée.#(cr)#(lf) at Microsoft.Mashup.Engine1.Language.ValueCreator.CreateValueForThrow(IThrowExpression throwExpr)#(cr)#(lf) at Microsoft.Mashup.Engine1.Language.ValueCreator.<>c__DisplayClass23_0.<CreateValueForRecord>b__0(Int32 index)#(cr)#(lf) at Microsoft.Mashup.Engine1.Runtime.RecordValue.DemandRecordValue.get_Item(Int32 index)#(cr)#(lf) at Microsoft.Data.Mashup.ProviderCommon.MashupResource.TryGetValue(Func`1 getValue, IValue& value, String& errorMessage)#(cr)#(lf)Record", Right = error "Microsoft.Mashup.Engine1.Runtime.ValueException: [Expression.Error] La valeur n'a pas été spécifiée.#(cr)#(lf) at Microsoft.Mashup.Engine1.Language.ValueCreator.CreateValueForThrow(IThrowExpression throwExpr)#(cr)#(lf) at Microsoft.Mashup.Engine1.Language.ValueCreator.<>c__DisplayClass23_0.<CreateValueForRecord>b__0(Int32 index)#(cr)#(lf) at Microsoft.Mashup.Engine1.Runtime.RecordValue.DemandRecordValue.get_Item(Int32 index)#(cr)#(lf) at Microsoft.Data.Mashup.ProviderCommon.MashupResource.TryGetValue(Func`1 getValue, IValue& value, String& errorMessage)#(cr)#(lf)Record"];Message.Format = Désolé... Nous n'avons pas pu appliquer l'opérateur #{0} aux types #{1} et #{2}.;Message.Parameters = {"-", "Table", "Table"};ErrorCode = 10051;Microsoft.Data.Mashup.Error.Context = System (Request ID: c9e39295-bda4-4ecf-9650-f0cd39e3204a).

The issue is really random — sometimes the run works fine, but since this morning it hasn’t worked at all.

Need your help, please

[v-dineshya]

Hi @XCT ,

Thank you for reaching out to the Microsoft Community Forum.

The error "We couldn't apply the operator '-' to types Table and Table" refers that somewhere in your Power Query logic, you are trying to subtract one table from another using the - operator, which is not valid in Power Query M language. This kind of operation might work in the Power Query Editor due to preview caching or partial evaluation, but fails during actual refresh in the service.

Please try below things to fix the issue.

1. Ensure you are not trying to subtract one table from another. If you are trying to filter out rows, consider using functions like Table.SelectRows, Table.RemoveRows, Table.Join and Table.ExceptShow.

2. If your want to remove rows from one table that exist in another, use
Table.Except(Table1, Table2), it subtract one table from another in Power Query.

3. The error "The value has not been specified", mean that one of the tables involved in the operation is null or not properly loaded. Ensure all queries return valid tables and that any parameters or steps are correctly defined.

4. Test Refresh in Power BI Service:
Sometimes, the Power Query Editor handles previews differently than the actual refresh engine. After making changes, test the refresh in the Power BI Service to confirm the fix.

5. If you are referencing queries that are not loaded ( "Enable Load" is unchecked), it might cause issues during refresh. Ensure all necessary queries are loaded.

6. If you are using dynamic parameters or functions that work differently during refresh like DateTime.LocalNow(), consider replace them with static values.

I hope this information helps. Please do let us know if you have any further queries.

Regards,

Dinesh

[v-dineshya]

Hi @XCT ,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. And, if you have any further query do let us know.

Regards,

Dinesh

[XCT · Accepted solution]

Hi,

I've found a workaround by :

1/ disableing the staging on the concerned table, then refresh the dataflow (the table dissapears but it's normal)

2/ then enabling the staging again on it and refresh the dataflow. 

It works again: the table is correctly overwrite in the staging Lakehouse

[v-dineshya]

Hi @XCT ,

Thanks for the update. We are happy to hear that you have resolved the issue. Thanks for sharing the details here.  And, if you have any further query do let us know.

Regards,

Dinesh