Skip to main content
cancel
Showing results for 
Search instead for 
Did you mean: 

Find everything you need to get certified on Fabric—skills challenges, live sessions, exam prep, role guidance, and more. Get started

Reply
Ben-Dev
Helper II
Helper II

Table.Combine Dies With Stack Overflow

Hello Microsoft Team,

 

I've stumbled across a stack overflow error which rears its ugly head if I try to Table.Combine two tables which are both based on Table.View. 😞

 

Any idea what's going on here, or suggestions on how we can prevent this? Is this a Power Query bug?

 

Cutting it down to the relevant code, here's a repo example which can be demoed in Power BI's Query Editor:

let
    GetView = (state as record) => 
        Table.View(
            null,
            [
                GetType = () => Value.Type(GetRows()),
                GetRows = () => #table({"Col1"}, {{"a"}}),
                OnTake = (count as number) => @GetView(state & [Take = count])
            ]
        )
    ,
    Table = GetView([])
in
    // * The following successfully return a table:
    // Table
    // Table.FirstN(Table, 1000)

    // * All of the following die with: 'Expression.Error: Evaluation resulted in a stack overflow and cannot continue.'
    // Table.FirstN(Table.Combine({Table, Table}), 1000)
    // Table.Combine({Table.FirstN(Table, 1000), Table.FirstN(Table, 1000)})
    Table.Combine({Table, Table})

 

The self-reference (i.e. the above combining Table with itself) doesn't appear to be the issue, as the stack overflow also occurs when two different views are involved:

let
    GetViewA = (state as record) => 
        Table.View(
            null,
            [
                GetType = () => Value.Type(GetRows()),
                GetRows = () => #table({"Col1"}, {{"a"}}),
                OnTake = (count as number) => @GetViewA(state & [Take = count])
            ]
        )
    ,
    GetViewB = (state as record) => 
        Table.View(
            null,
            [
                GetType = () => Value.Type(GetRows()),
                GetRows = () => #table({"Col1"}, {{"a"}}),
                OnTake = (count as number) => @GetViewB(state & [Take = count])
            ]
        )
in
    Table.Combine({GetViewA([]), GetViewB([])})

 

Help here would be much appreciated! Thank you!

4 REPLIES 4
v-jingzhang
Community Support
Community Support

Hi @Ben-Dev 

 

I tested with a simple Table view. It can be combined with itself. 

vjingzhang_0-1653980065243.png

vjingzhang_1-1653980471533.png

Perhaps the issue is due to the code for generating your table view?  

 

Best Regards,
Community Support Team _ Jing

Thanks, @v-jingzhang!

 

I believe the issue here may be related to the combination of Table.Combine and OnTake. From what I'm hearing, sounds like there's an underlying issue which I'll just have to live with.

AlexisOlson
Super User
Super User

I don't know if this helps whatever your ultimate goal is but you can avoid the error by buffering Table to memory.

 

That is, replace 

Table = GetView([])

 with

Table = Table.Buffer(GetView([]))

Hi @AlexisOlson, thanks!

 

Unfortunatley, since buffering blocks subsiquent folding and the real-life Table.View handles more complex folding than is shown in the example, I'm not sure I can realistically use buffering. 

Helpful resources

Announcements
July 2024 Power BI Update

Power BI Monthly Update - July 2024

Check out the July 2024 Power BI update to learn about new features.

PBI_Carousel_NL_June

Fabric Community Update - June 2024

Get the latest Fabric updates from Build 2024, key Skills Challenge voucher deadlines, top blogs, forum posts, and product ideas.

Top Solution Authors
Top Kudoed Authors